Plasmonic sensor device, sensor system and sensing method

Abstract

Plasmonic biosensor device comprising a first and second electrode, a charge carrier tunnelling junction for providing charge carriers for generating electroluminescent light emission, that is in electrical connection with the first and second electrodes for application of a voltage potential difference. The second electrode comprises or forms a plasmonic structure including a plurality of optical nanoantennas or a plurality of electrically interconnected optical nanoantennas configured to generate plasmons and light emission via the charge carriers provided by charge carrier tunneling in the charge carrier tunnelling junction. The plurality of optical nanoantennas extend thereon.

Description

[0001] PLASMONIC SENSOR DEVICE, SENSOR SYSTEM AND SENSING METHOD

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] The present application claims priority to European patent application No. 24208501 .7 filed on October 23rd, 2024, the entire contents thereof being herewith incorporated by reference.

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to a sensor device, in particularly a plasmonic sensor device and more particularly a plasmonic sensor device including an embedded source of light provided by a quantum tunnel junction. The present invention relates to a sensor system or point-of-care device including such a plasmonic sensor device, and a sensing method performing sensing using the plasmonic sensor device.

[0006] BACKGROUND

[0007] Optical metasurfaces provide an ideal platform for refractometry sensing because they produce strong optical field confinement and enhancement over extended regions that allow to identify deep-subwavelength layers of organic and inorganic molecules.

[0008] However, the use of external light sources is necessary. The requirement of using external light sources involves bulky equipment and increases the sensing system size. This hinders the provision of point-of-care applications and point-of-care sensor devices.

[0009] Plasmonic metal nanostructures have been intensively investigated as a platform for optical sensors due to their unique abilities to simultaneously support strong optical field enhancement and deep-subwavelength light confinement via localized surface plasmon resonances (SPRs) and propagating surface plasmon polaritons (SPPs). Based on these assets, biosensing devices rapidly excelled the detection performance of conventional optical sensors, paving the way for widespread use and commercialization. Surface plasmon resonance (SPR) biosensors based on flat metal films have become one of the gold-standard label-free techniques for real-time monitoring of biomolecular interactions in both applied and fundamental bioanalytical studies.

[0010] Concurrently, nanostructured surfaces and nanoantennas featuring localized plasmonic resonances enabled furtherenhancement of the sensitivity and facilitated multiplexed sensing. Compact footprint of such nanoplasmonic biosensors also allowed to minimize the sample volumes in portable device configurations and even observe real-time single cell secretion. More recent advances are exploring quantum plasmonic sensing regimes to uncover new opportunities for enhanced device performance detection down to single-molecule level.

[0011] Despite significant progress in nano-photonics, the excitation of surface plasmon polaritons (SPPs) mostly requires an external light source as well as bulky coupling schemes, such as prisms, grating couplers or tightly focusing optics, which limit the usability of plasmonic sensors in biochemical research and medical diagnostics where miniaturized and integrated devices are crucial especially at point-of-care (POC) settings.

[0012] In this regard, electrical excitation of surface plasmon polaritons (SPPs) constitutes a desirable goal to achieve the ultimate on-chip integration and compact device footprint for applications in biosensing and beyond. In 1976, J. Lambe and S. L. McCarthy discovered light generation through electron tunneling in thin film heterostructures with a metal (Al)-insulator (AhOsJ-metal (Au) configuration. These pioneering observations showcased the possibility of direct and ultrafast transduction between electrons and photons, as the excess energy of the tunneling electrons can generate light via radiative decay assisted by the intermediate excitation of plasmons. Applications of this phenomenon have been so far mostly associated with scanning tunneling microscopy (STM) operating in ultrahigh vacuum environments and allowing the mapping of photon emission with exceptional spatial resolution. STM proved itself useful for probing molecular vibrations, visualizing electronic wave functions and molecular orbitals, exploring intermolecular coupling, and scrutinizing the dynamics of adsorbate molecules.

[0013] More diverse applications of light emission from inelastic electron tunneling (LIET) are largely hindered by its extremely low intensity, which is the combined result of low (on the order of 10’6) efficiency of the process and small emission area. Many efforts have been devoted to enhancing it both from material science and nano-photonics research viewpoints. One of the parameters in devices relying on the LIET process is the quality of the electron tunnel barrier. Grain formation and defects of the isolating layer can undermine the stability and efficiency of the insulator junction considerably, thereby necessitating advanced thin film deposition techniques to form sufficiently smooth layers that are immune to such problems.

[0014] In this context, 2D materials offer notable advantages owing to their crystalline structure and atomically flat interfaces. In particular, hexagonal boron nitride (h-BN) with its large (~6 eV) bandgap and excellent crystalline quality can serve as a suitable tunneling barrier material, while graphene or transition metal dichalcogenides can act as either electrical contacts or additional modulators of the LIET efficiency thanks to their optical and electrical characteristics and their tunability via electrical gating. Additionally, barrier engineering through quantum wells has been demonstrated to introduce resonant inelastic electron tunneling, enhancing efficiency considerably. However, 2D materials are so far poorly compatible with large scale fabrication approaches, where a much bigger emission area could compensate for smaller photon yield.

[0015] An increase in the LIET efficiency can be achieved by using resonant optical nanoantennas. Enhancement of the detected LIET from a tunnel junction with a plasmon ic nanoantenna was reported experimentally and later explained theoretically by showing that the nanoantenna radically increases the electromagnetic local density of states and enhances radiative emission by orders of magnitude, thus overcoming nonradiative decay processes, that are otherwise dominant in conventional tunnel junctions. Additional enhancement of the measured LIET signal is also achieved due to the ability of nanoantennas to steer the radiation toward the detector when they are designed to exhibit a directional emission pattern. Furthermore, the resonant response of nanoantennas can be tailored such that they shape the spectrum of the inherently broadband LIET emission.

[0016] Assisted by nanophotonic designs and newly available materials, light emission from inelastic electron tunneling LIET sources have been leveraged for a broad range of applications that include ultra-compact waveguide-integrated light sources, spectroscopic detection of nanoscale distances, on-chip data communication, and enhancement and in-situ tracking of chemical reactions. Recent studies reported LIET efficiencies surpassing 1% but achieving uniform emission over a larger area with stable electrical biasing, and minimizing issues such as blinking still remain a challenge. Addressing these issues is pivotal for the design of integrated devices incorporating tunneling devices in applications such as biosensing.

[0017] US2023 / 0207726 discloses an optical device for generating light. The device includes a silver nanorod upon which an ITO layer is provided. The thickness of the ITO layer is such that biosensing of an object on the device is prevened due to the significant separation of the silver nanorod from the object by the ITO layer.

[0018] A goal of the present invention is to provide a solution to the above-mentioned inconveniences, or at least one of the above-mentioned inconveniences.

[0019] SUMMARY

[0020] It is therefore one aspect of the present disclosure to provide a plasmon ic device orplasmonic biosensor device, in particular, a plasmonic device or plasmonic sensor device that addresses the above-mentioned inconveniences and needs. The plasmonic device may comprise a first electrode or at least one first electrode, a second electrode or at least one second electrode, and at least one charge carrier tunnelling junction for providing charge carriers for generating light emission or electroluminescent light emission, the at least one charge carrier tunnelling junction being in electrical connection with the first electrode and the second electrode for application of a voltage potential difference to the at least one charge carrier tunnelling junction. The second electrode may comprise or form at least one or a plasmonic structure including a plurality of optical nanoantennas ora plurality of electrically interconnected optical nanoantennas configured to generate plasmons or surface plasmons and light emission via the charge carriers provided by charge carrier tunneling in the at least one charge carrier tunnelling junction. The plurality of optical nanoantennas may be located and extend on the at least one charge carrier tunnelling junction.

[0021] The nanoantennas may each include a sensing surface, and the sensing surfaces may be disposed on the plasmonic biosensor device to receive, directly or indirectly on the sensing surface, at least one of an entity, analyte and substance to wavelength shift at least one spectral portion of the luminesce emission spectrum of the plasmonic biosensor device and / or change an intensity of the at least one spectral portion of the luminesce emission spectrum of the plasmonic biosensor device.

[0022] The sensing surfaces may be disposed on the plasmonic biosensor device to receive, directly or indirectly on the sensing surface, at least one of the entity, analyte and substance to wavelength shift a plasmonic spectral feature of the luminesce emission spectrum of the plasmonic biosensor device. Light at, at least one wavelength in a spectral range of the plasmonic spectral feature, may be wavelength shifted.

[0023] The sensing surfaces may be disposed on the plasmonic biosensor device to receive, directly or indirectly on the sensing surface, the at least one of the entity, analyte and substance to change an intensity of the light at the at least one wavelength.

[0024] The at least one wavelength may be at an emission intensity peak value or at least one emission intensity peak value of the plasmonic spectral feature.

[0025] The optical nanoantennas may be physically interconnected optical nanoantennas, each optical nanoantenna may comprises or be made of at least one metal, and the plurality of optical nanoantennas may be interconnected by at least one interconnection comprising or being made of the same at least one metal. The plasmonic structure may include a plurality of interconnections electrically and physically interconnecting the plurality of optical nanoantennas. The optical nanoantennas may extend in a first elongated direction and the plurality of interconnections may extend in a second elongated direction different to the first elongated direction. The second elongated direction may be traverse to the first elongated direction.

[0026] A length of the optical nanoantenna extending in the first elongated direction may be greater than a width of interconnection extending in a direction traverse to the first elongated direction.

[0027] The plasmonic structure may include a plurality of interconnections electrically and physically interconnecting the plurality of optical nanoantennas. The plurality of interconnection and the plurality of nanoantennas may extend to form or define a mesh structure of interlinked optical nanoantennas. The interconnections and the optical nanoantennas may comprise or be made of the same at least one metal.

[0028] A length of the optical nanoantenna extending in an elongated direction of extension of the optical nanoantenna may be between 10 and 10000 times greater than a width of the optical nanoantenna extending traverse to the elongated direction of extension.

[0029] The first electrode, the at least one charge carriertunnelling junction and the second electrode may form a multilayer device and / or a superposed stacked layer device to define or form a planar device geometry.

[0030] The at least one charge carrier tunnelling junction may be a planar tunnelling junction and the plurality of optical nanoantennas may be superposed thereon to extend across the at least one charge carrier tunnelling junction.

[0031] The plasmonic structure may define or form a plasmonic metasurface, and the plasmonic structure is configured to generate plasmons or plasmonic surface lattice resonances; or at least one of plasmons and plasmonic surface lattice resonances.

[0032] The plasmonic structure may define or form an electric contact with the at least one charge carrier tunnelling junction and may define or form at least one optical interface for light emission. The electroluminescent light emission and plasmon generation may be produced by charge carriers provided by the at least one charge carrier tunnelling junction by inelastic tunnelling in the at least one charge carrier tunnelling junction. The second electrode may be in electrical connection with the at least one charge carrier tunnelling junction to generate charge carriers by charge carrier tunneling in the at least one charge carrier tunnelling junction, and the second electrode my generates and emit the light emission and luminesce emission spectrum of the plasmonic biosensor device.

[0033] The optical nanoantennas or each optical nanoantenna may be an optically resonant nanoantenna supporting a resonant mode at an optical frequency. The optical nanoantennas or each optical nanoantenna may have an optical sub-wavelength dimension at a wavelength corresponding to a resonant mode optical frequency of the optical nanoantenna.

[0034] The plasmonic structure and the plurality of optical nanoantennas may be configured to generate plasmons or plasmonic surface lattice resonances providing electric field localization and enhancement at a sensing surface of the plasmonic structure and the optical nanoantennas.

[0035] The plasmonic structure and the plurality of optical nanoantennas may be configured to generate counter-propagating plasmonic lattice modes in the plasmonic structure to provide an optical band gap in a spectral region of the electroluminescence of the plasmonic biosensor device.

[0036] The plurality of optical nanoantennas may be arranged in at least two orthogonal directions with differing periodicities to generate at least one plasmonic lattice mode across the at least one charge carrier tunnelling junction.

[0037] The plasmonic structure may include a plurality of intersections electrically interconnecting the plurality of optical nanoantennas. The optical nanoantennas of the plurality of optical nanoantennas may extend in a first direction and the plurality of intersections may extend in a second direction different to the first direction.

[0038] The plasmonic structure may include a plurality of arrays of physically interconnected optical nanoantennas physically interconnected by the plurality of intersections. The arrays may extend in the first and second directions.

[0039] The plasmonic structure may include a plurality of arrays of optical nanoantennas extending in the first direction. The optical nanoantennas of the arrays that extend in the first direction may be periodically located on the at least one charge carrier tunnelling junction. The plasmon ic structure may include a plurality of arrays of optical nanoantennas extending in the second direction. The optical nanoantennas of the arrays that extend in the second direction may be periodically located on the at least one charge carrier tunnelling junction.

[0040] A periodic separation distance of the optical nanoantennas of the array extending in the first direction may be greater than a periodic separation distance of the optical nanoantennas of the array extending in the second direction.

[0041] The at least one charge carrier tunnelling junction may be an electron tunnelling insulator junction. The first electrode may comprise at least one metal, the second electrode may comprise at least one metal, and the at least one charge carrier tunnelling junction may comprise at least one insulator.

[0042] The at least one charge carrier tunnelling junction may include a single tunnelling insulator layer in which or through which electron tunneling occurs. The single tunnelling insulator layer may comprise aluminum oxide AI2O3. The single tunnelling insulator layer may have a thickness less than 10nm.

[0043] The at least one charge carrier tunnelling junction may be an electron tunnelling insulator junction located between the first and second electrodes, and the at least one charge carrier tunnelling junction may include a layer comprising aluminum oxide AI2O3, the layer may have a thickness less than 10nm.

[0044] The at least one charge carrier tunnelling junction may be an electron tunnelling insulator junction located between the first and second electrodes, and the at least one charge carrier tunnelling junction, in which or through which electron tunneling occurs, may consists of a single layer comprising aluminum oxide AI2O3. The at least one charge carrier tunnelling junction may include at least one insulator layer comprising aluminum oxide AI2O3, and the first electrode may comprise aluminum.

[0045] The at least one charge carrier tunnelling junction may be a non-MQW tunnelling junction, that is, a non metallic-quantum-well tunnelling junction.

[0046] It is another aspect of the present disclosure to provide a sensing method carried out using the plasmonic sensor device. The method may include providing at least one plasmonic biosensor device; providing at least one sample for analysis or investigation to the at least one plasmonic biosensor device; and generating light emission by the at least one plasmonic biosensor device.

[0047] The method may include measuring the generated light emission to determine a wavelength shift in a luminesce emission spectrum and / or an augmentation in intensity of the luminesce emission spectrum.

[0048] The method may include measuring the generated light emission to determine a wavelength shift of at least one spectral portion of the generated luminesce emission spectrum of the plasmonic biosensor device when the at least one sample for analysis or investigation is provided compared to prior to the provision of the at least one sample for analysis or investigation.

[0049] The method may include measuring the generated light emission to determine a wavelength shift of a plasmonic spectral feature of the generated luminesce emission spectrum. The wavelength shift may be determined at at least one wavelength in the spectral range of the plasmonic spectral feature.

[0050] The method may include measuring the generated light emission to determine a change in light intensity of at least one spectral portion of the generated luminesce emission spectrum of the plasmonic biosensor device when the at least one sample for analysis or investigation is provided compared to prior to the provision of the at least one sample for analysis or investigation.

[0051] The method may include measuring the generated light emission to determine the change in light intensity of a plasmonic spectral feature of the generated luminesce emission spectrum.

[0052] The method may include measuring the generated light emission to determine the change in light intensity at the least one wavelength of the plasmonic spectral feature. The at least one wavelength may be at an emission intensity peak value or at least one emission intensity peak value of the plasmonic spectral feature.

[0053] The method may include measuring the generated light emission to determine the change in light intensity in a wavelength window or range of the plasmonic spectral feature. The change in light intensity in the wavelength window or range of the plasmonic spectral feature may comprise determining or calculating at least a differential between (i) light intensity in the wavelength window or range when the at least one sample for analysis or investigation is provided and (ii) light intensity in the wavelength window or range prior to the provision of the at least one sample for analysis or investigation. An average value may be determined by averaging the determined differential over wavelength values of the wavelength window or range.

[0054] Specific embodiments and other advantageous features can be found in the dependent claims.

[0055] The plasmonic sensor advantageously comprises an embedded source of light provided by a quantum tunnel junction.

[0056] The plasmonic structure and the plurality of interconnected optical nanoantennas permit light emission and emission enhancement to be obtained and controlled, allows to define or control the spectral content of the emitted light, permits to determine directivity of the light emission of the sensor device. This assures the provision of a sensor device of high sensitivity, reactivity and / or responsivity for detection or sensing of one or more of an entity, analyte and substance. The plasmonic sensor advantageously allows to provide light emission over a large area.

[0057] The plasmonic sensor advantageously allows to provide substantially uniform emission over large areas.

[0058] In an embodiment, an optically resonant nanoantenna / nanowire metasurface may serve as a top contact for the junction and provides uniform emission over large areas, amplified by nanoantenna modes that simultaneously enhance the spectral and refractive-index sensitivity.

[0059] In an embodiment, the resonant nanoantenna / nanowire is doubly periodic to advantageously further improve light emission uniformity over large areas.

[0060] Spatially resolved refractometric sensing measurements of nanometer-thick polymer coating and protein layer are provided as exemplary results demonstrating the advantages and capability of this disruptive platform for, for example, integrated electro-optical biosensors.

[0061] The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description with reference to the attached drawings showing some preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention.

[0063] Figure 1A is a schematic of an exemplary embodiment of a plasmonic sensor device or plasmonic biosensor device. The specifically mentioned materials, thicknesses and voltages indicated in the Figures are merely exemplary and non-limiting exemplary materials, thicknesses and voltages. The device may be or may form a biosensor, for example, a label-free on-chip biosensor based on light emission from metasurfaces driven by quantum electron tunneling. The device is a quantum tunneling-based sensing device. The inset of Figure 1A shows a cross-sectional exemplary layer sequence of a device according to one exemplary non-limiting embodiment comprising: A gold doubly periodic metasurface with a thin Cr adhesion layer separated by an AI2O3 tunneling barrier from a 25 nm Al film deposited on glass substrate.

[0064] Figure 1 B shows an energy level diagram for a metal-insulator-metal (MIM) tunnel junction of the plasmonic sensor device illustrating the possible electron pathways and plasmon / photon emission driven by inelastic tunneling.

[0065] Figure 1C Illustrates an exemplary quantum tunneling-assisted sensing principle of the present disclosure. The bare device surface or bare metasurface (left curve) exhibits a tunneling luminescence peak that is red-shifted and enhanced when the device surface or the metasurface is provided with or covered by an analyte (right curve).

[0066] Figure 1 D, from left to right, respectively shows an optical microscope image (i) of an array of devices electrically connected to metallic pads on a printed circuit board (PCB), an enlarged optical image (ii) from panel (i) and scanning electron microscope (SEM) image (iii) of the metasurface, a high-resolution transmission electron microscopy image (iv) of a thin lamella cut from the metasurface, further zoom-ins (v)(vi) of a single antenna and the tunneling gap give an estimate for the thicknesses of the AI2O3 insulator gap (5 nm) and the Cr adhesion layer (5 nm).

[0067] Figure 1 E is a schematic of an exemplary embodiment of a plasmonic sensor device. Figures 1 F and 1G are schematics of an exemplary layout of nanoantennas and metasurfaces of an exemplary embodiment of a plasmonic sensor device.

[0068] Figure 1 H is a schematic of an exemplary nanoantenna of an exemplary embodiment of a plasmonic sensor device.

[0069] Figures 11 is a schematic of an exemplary layout of nanoantennas and metasurfaces of an exemplary embodiment of a plasmonic sensor device.

[0070] Figures 2a to 2g show an exemplary fabrication method of a plasmonic sensor device of the present disclosure and show an exemplary fabrication flow to produce the device comprising self-illuminated plasmonic metasurfaces, and Figure 2h is a cross-sectional TEM image of a single nanowire antenna, and Figure 2i is a schematic top view of the exemplary fabricated device. As previously mentioned, the specifically mentioned materials and thicknesses and layout indicated in the Figures are exemplary.

[0071] Figures 3a to 3e show an electro-optical characterization of plasmonic sensor device having a large-area metasurface. The top portion of Figures 3a and 3b show optical microscope images of the light emission from a, a metasurface consisting of 1 D array of horizontal nanowires with an exemplary period Px of 400 nm in the vertical direction (Figure 3a) and a doubly periodic metasurface formed by densely interconnected 2D arrays of nanowires with an exemplary period Px, Py of 400 nm in both directions, that is, the vertical direction and the horizontal direction (Figure 3b), while the bottom portions of Figures 3a and 3b show the corresponding SEM images. Figure 3c (top portion) is an image of the spatially homogeneous and electrically stable light emission from an improved or optimized doubly periodic metasurface formed by less densely interconnected 2D arrays of nanowires with an exemplary 400 nm period Px in the vertical direction and 100 pm period Py in the horizontal direction, the inset shows a measured angular distribution of the tunneling luminescence with different orientation of the analyzer, illustrating that the observed emission has a dipolar nature. The bottom portion of Figure 3c is a SEM image of the metasurface. The scale bar in Figure 3c is common for all three panels of Figures 3a to 3c. Figure 3d show the l-V curve of the metasurface of Figure 3c and shows the simultaneous light emission from this tunneling device (dark curve). The range of voltages above the field emission threshold is shaded. Figure 3e shows the corresponding Fowler-Nordheim representation of the l-V data (lighter curve) and its fitting to the Simmons model (black curve). The field emission region (shaded) is clearly defined by the sharp bend of the curve at 0.8 V. Below 0.8 V (above 1 .25 in 1 / V), the signal is dominated by direct electron tunneling. Figures 4a to 4e show experimental and theoretical analysis of the spectral response in light emission from inelastic tunneling (LET). Electroluminescence spectra from the device having the improved or optimized metasurface for various applied voltages ranging from 1 ,5V to 2.3V as obtained from experimental measurements (Figure 4a) and theoretical calculations (Figure 4b). Figure 4c shows calculated external quantum efficiency (upper curve) and its correlation to the experimental emission spectra (lower curve) at a bias voltage Vp=2.3V, where the insets show the calculated electrical field amplitude distribution in the x-z plane for linearly polarized plane wave excitation at two characteristic wavelengths: 650 nm (left dashed line) and 900 nm (right dashed line). Figure 4d shows calculated normalized tunneling efficiency H(OJ) for Vb=2.3V. Figure 4e shows calculated normalized radiation efficiency G(OJ).

[0072] Figures 5a to 5f show a demonstration of label-free biosensing by electron-tunneling-induced light emission by the device having an improved or optimized metasurfaces. Figure 5a is an image of the homogeneous light emission from the optimized metasurface with (lower box: Analyte region of interest (ROI) and without (upper box: Bare ROI) a coating PMMA thin film. Figure 5b is a spectral response from the boxed regions in Figure 5a with / without PMMA. Figure 5c shows simulated emission spectra under the conditions of Figure 5b. Figure 5d is an image of the light emission from the metasurface of the device with (upper left box: Analyte ROI) and without (bottom right box: Bare ROI) a deposited layer of protein A / G molecules. Figures 5e and 5 show matching spectral response for these ROIs showing the influence of protein addition.

[0073] Figures 6A to 6G show characterization of surface features after functionalization of the LET device with either PMMA or protein AG as measured by an optical microscope (Figure 6A,6D to 6E), by Electron-multiplying CCD (Figures 6B and 6F), and antenna line profiles with and without the analyte in (Figures 6C and 6G) extracted from 2D AFM scans.

[0074] Figures 7A and 7B are schematics of the electroluminescence characterization setup, where Figure 7A shows an optical path of real (thinner and light gray line) and back-focal plane (thicker and darker line) imaging, respectively, and Figure 7B shows the optical path for a spectrum measurement and a device position relative to the objective.

[0075] Figure 8 shows the effect of in-plane momentum conservation, and a comparison of the tunneling efficiency H(OJ, Vb) calculated with and without imposing in-plane momentum conservation. Electrons tunnel from a polycrystalline Al layer to the polycrystalline Cr layer. The bias voltage Vb ranges from 1 .5 V to 2.3 V.

[0076] Figure 9 shows angle-resolved radiation efficiency G(w,0,(p) at selected wavelengths from 500 nm to 725 nm. Results are shown up to a maximum polar angle 0 = 54°, as determined by the numerical aperture NA= 0.8 of the objective used in experiment to collect the emission signal.

[0077] Figure 10 schematically shows a sensor system or point-of-care device including the plasmon ic sensor device of the present disclosure.

[0078] Figure 11 schematically shows an exemplary plasmonicsensordevice or plasmonic biosensor device of the present disclosure.

[0079] Figure 12A shows results of theoretical modeling of angle-resolved reflectance spectrum depending on the thickness of a) resonator (HAU), b) insulator layer (HAI2OS) and c) periodicity of the x-direction nanowire (Px). Figure 12B shows results of theoretical modeling in which the width of the x-direction (Wx) nanowires is varied.

[0080] Figure 13 shows exemplary cross-sectional shape of a nanowire.

[0081] Figures 14Aand 14C are top view schematics of 1- dimensional and 0- dimensional structures, and illustrate the shape of the resonator and its configuration on the insulator from a top view, Figure 14B shows a device including 1-dimensional shaped resonators on the insulating layer.

[0082] Figure 15 shows the measured results of a further evaluation of the sensing performance of the device of the present disclosure based on the exemplary layout design shown in Figure 1A. As demonstrated in Figure 15, the sensing capability was assessed by measuring and quantifying biomolecules (L-Alanine) of varying thicknesses. The limit of detectable analyte thickness in the exemplary design is below 5 nm.

[0083] Figure 16a shows the results of an AFM measurement of plasmonic nanowires of a first exemplary design, Figure 16b shows the results of an AFM measurement of plasmonic nanowires of a second exemplary design. Figures 16c and 16d are color maps of theoretically modelled angle-resolved reflectance spectra of the first design and the second design. Figure 16e shows electroluminescence emission spectra of the device of the second design. Figures 17a and 17b show the results of FMM calculation carried out for design 1 and design 2.

[0084] Figures 18a shows measured angle-resolved reflection spectra for design 1 , Figure 18b with analyte (~35 nm thickness, D-Alanine), and Figure 18c shows emission spectra for design 1. Figures 18d shows measured angle-resolved reflection spectra for design 2, Figure 18e with analyte (~35 nm thickness D-Alanine), and Figure 18f shows emission spectra for design 2.

[0085] Figure 19 shows the results of sensing performance experiments of design 2. The top panels show the EL spectra of the pristine and spotted spectra. The bottom panels show the ratio of the EL difference normalized on the pristine EL for each wavelength.

[0086] Figures 20a to 20c shows generated light’s emission directions, on a collection side and a sensing side.

[0087] Figures 21a and 21b show experimental data for collected light from the top and bottom (backside of the chip) of the device.

[0088] Herein, identical reference numerals are used, where possible, to designate identical elements that are common to the Figures. Also, the images are simplified for illustration purposes and may not be depicted to scale. Any of the embodiments described herein may be used in combination with any other embodiment described herein.

[0089] DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

[0090] Figures 1 A, 1 B and 1 E shows exemplary devices or plasmonic sensor devices 1 according to the present disclosure. The plasmonic sensor device 1 may be, for example, a plasmonic biosensor device 1.

[0091] The plasmonic sensor device 1 is, for example, configured to electrically generate plasmons and photons. The photons or emitted light or electroluminescence is, for example, generated by electrically driven plasmons.

[0092] The plasmonic sensor devicel comprises for example at least one or a first electrode or electrical connection 3, at least one or a second electrode or electrical connection 5 and at least one charge carrier tunnelling junction or barrier 7. The charge carrier tunnelling junction 7 is, for example, located between the first electrode 3 and the second electrode 5. The charge carrier tunnelling junction 7 can be, for example, an electron tunnelling junction. In an embodiment, the plasmonic device 1 may include at least one support or substrate 19 supporting the first electrode 3, the charge carrier tunnelling junction 7 and the second electrode 5. The support or substrate may, for example, comprises or consist of glass or SiC>2.

[0093] The charge carrier tunnelling junction 7 is configured to provide charge carriers or tunnelling charge carriers for generating light emission via inelastic charge carrier (electron) tunnelling.

[0094] The charge carrier tunnelling junction 7 is in electrical connection with the first electrode 3 and the second electrode 5. This permits the application of a potential difference (or voltage potential difference) across or to the charge carrier tunnelling junction 7 to allow charge carriers to tunnel across orthrough the junction 7 to the second electrode 5, orto allow charge carriers to tunnel across orthrough the junction 7 to the electrode from which light emission is to occur.

[0095] In an embodiment, a bias voltage Vbmay, for example, be applied to the first electrode 3 which the second electrode 5 is grounded resulting in a voltage potential difference being applied to or across the charge carrier tunnelling junction 7. The bias voltage Vbmay, for example, be a positive voltage to permit electron tunneling through the tunnelling junction 7. The voltage potential difference applied is inferiortothe breakdown voltage ordielectric breakdown voltage of the tunnelling junction 7 orthe constituent material of the tunnelling junction 7.

[0096] The charge carrier tunnelling junction 7 is, for example, an insulator junction or insulator barrier. The charge carrier tunnelling junction 7 comprises or consists solely of at least one insulator or insulator material. The charge carrier tunnelling junction 7 may comprise at least one electrically insulating material or layer, or consist of an electrically insulating material or layer.

[0097] In an embodiment, the charge carrier tunnelling junction or layer 7 (or a portion thereof or a surface thereof (for example closest to the second electrode 5) may for example comprise or consist of or be, a non-deposited material or layer, and / or a thermally oxidized material or layer, and / or a material or layer formed through thermal oxidation of a first or supporting layer or material that may be for example a deposited material or layer that subsequently oxidized). This assures a highly uniform barrier / and / or a high-quality tunneling contact.

[0098] The insulating material or layer of charge carriertunnelling junction 7 may be, or may comprise or consist of, forexample, at least one metal oxide, for example, aluminium oxide, HfO2, ZrO2, orTi02. In one preferred embodiment, the insulating material or layer may comprise or consist of aluminum oxide. Other metal oxides may preferably be metal oxides whose bandgap is comparable with that of aluminium oxide allowing a switch on threshold voltage of the device 1 to be similar, and permitting threshold voltage operation avoiding or reducing significant leakage current.

[0099] The insulating material or layer of charge carriertunnelling junction 7 may be, or may comprise or consist of, for example, 2D material-based layers, such as h-BN, or a TMDC material, including MoS2, WSe2, or WS2.

[0100] The charge carriertunnelling junction 7 is, for example, an electron tunnelling insulator junction or electron tunnelling insulator barrier.

[0101] The charge carrier tunnelling junction 7 is, for example, electrically insulating and / or of lower electrical conductivity than the first electrode 3 and the second electrode 5. The charge carrier tunnelling junction 7 has a thickness t1 extending (for example in a z-direction) between the first electrode 3 and the second electrode 5 that permits charge transfer by charge carrier tunneling (for example, electron tunnelling) through the insulating material ofthe charge carrier tunnelling junction 7 from the first electrode 3 to the second electrode 5, and permits a charge flow by displacement of charge carriers by tunnelling through from the insulator charge carrier tunnelling junction 7. The thickness t1 is typically small orthin, for example, between 1nm and 20nm, the specific thickness value being chosen as a function of the material of the junction 7.

[0102] The charge carrier tunnelling junction 7 being an electrical insulator or being electrically insulating acts, for example, as a barrier or potential barrier to charge transfer and current flow between the first electrode 3 and the second electrode 5, although allowing charge transfer and flow between the first electrode 3 and the second electrode 5 by tunnelling or quantum tunnelling, where such tunnelling or quantum tunnelling permits penetration of charge carriers through the potential barrier of the junction 7 and through the junction 7. The tunnelling or quantum tunnelling is inelastic tunnelling where the charge carrier (electron) provides a portion of its energy for light emission and a portion for plasmon excitation or generation.

[0103] In an embodiment, The charge carrier tunnelling junction 7 may include a single tunnelling insulator layer in which or through which electron tunneling occurs. The single tunnelling insulator layer comprises, for example, aluminum oxide AI2O3. The charge carrier tunnelling junction 7, in which or through which electron tunneling occurs, may for example, consists of a single layer comprising aluminum oxide AI2O3. The tunnelling insulator located between the first and second electrodes may be, for example, a single insulator layer or consists solely of insulator layers. The tunnelling insulator located between the first and second electrodes may be, for example, barrier metal-free.

[0104] The tunnelling insulator layer or single tunnelling insulator layer 7 may have a thickness less than about 10nm, or preferably less than about 9nm, or more preferably less than about 7.5 nm or most preferably less than about 54nm.

[0105] Such thin layers assure a higher number of tunneled electrons and light emission. The higher resulting light intensity is advantageous forthe application of biosensing. High thickness can prevent inelastic quantum electron tunneling due to the thick tunneling barrier.

[0106] The charge carrier tunnelling junction 7 may be, for example, an electron tunnelling insulator junction located between the first and second electrodes 3, 5 and the charge carrier tunnelling junction 7 may include a layer comprising aluminum oxide AI2O3 having a thickness less than 10nm (or less than about 10nm) or preferably less than 9nm (or less than about 10nm), or more preferably less than 7.5 nm (or less than about 7.5nm) or most preferably less than 4nm (or less than about 4nm).

[0107] In an embodiment, the charge carrier tunnelling junction includes at least one insulator layer comprising aluminum oxide AI2O3, and the first electrode 3 comprises aluminum.

[0108] The charge carrier tunnelling junction 7 may be, for example, a non-metallic-quantum-well tunnelling junction.

[0109] The fabricated charge carrier tunnelling junction 7 can thus be of high quality and has a thickness that can be precisely controlled. The tunnelling component can thus be of reduced complexity and include a reduced number of constituent elements or layers. The first electrode 3, second electrode 5 and charge carrier tunnelling junction 7 structure allows a direct current path from the first electrode 3 to the light emitting second electrode 5, that assures both an electrical and light emitting role or function.

[0110] The second electrode 5 (and plasmonic structure 11) can, for example, be directly connected to the external bias or electrical source, or directly connected to biasing circuitry that permits a voltage potential difference to be applied to the charge carrier tunnelling junction. The first electrode 3 forms an electrical contact or is in electrical contact directly or indirectly with the charge carrier tunnelling junction 7. The second electrode 5 also forms an electrical contact or is in electrical contact with the charge carrier tunnelling junction 7.

[0111] In an embodiment, at least one adhesion layer 9 may optionally be included between the second electrode 5 and to the charge carrier tunnelling junction 7. The adhesion layer 9 directly contacts the second electrode 5 and the charge carrier tunnelling junction 7. This permits to attach or improve the attachment of the second electrode 5 to the charge carrier tunnelling junction 7. The adhesion layer 9 may, for example, comprises at least one metal, the metal being for example different to that of the second electrode 5. In an embodiment, at least one adhesion layer may similarly be included between the first electrode 3 and to the charge carrier tunnelling junction 7. A thickness of the adhesion layer 9 is typically smaller than that of the electrode, for example, between 5 and 12 times smaller, for example, between 3 to 5 nm, or between about 3nm to about 5nm.

[0112] The first electrode 3 is, for example, a conductive electrode and / or comprises at least one metal. The first electrode 3 comprises, for example, at least one electrically conductive material. The metal may be, for example, a noble metal (for example ruthenium (Ru), or rhodium (Rh), or palladium (Pd), or silver (Ag), or osmium (Os), or iridium (Ir), or platinum (Pt), or gold (Au)). The metal may be, for example, aluminium or copper (Cu), or Molybdenum (Mo).

[0113] The second electrode 5 is, for example, a conductive electrode and / or comprises at least one metal. The second electrode 5 comprises, for example, at least one electrically conductive material. The metal permits the generation of plasmons or surface plasmons when excited by inelastic charge carrier (electron) tunneling through the junction 7, and the emission of light (photons).

[0114] The metal may be, for example, a noble metal such as gold (Au). The metal may for example be at least one of ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au). The metal may, for example, be the same those stated above forthe first electrode 3. The first and second electrodes 3, 5 may for example comprise or consist of the same metal or metals, a different metal or metals.

[0115] The first electrode 3 and / or second electrode may for example, comprise or consist of conductive graphene. In an embodiment, the first electrode 3 and / or the second electrode 5 comprise at least one crystalline surface having a defined crystal orientation in contact with the charge carrier tunnelling junction 7. This permits to exploit the effect of conservation of in-plane charge carrier (electron) momentum of the charge carriers (electrons) passing from the first electrode to the junction 7 and permit to enhance tunnelling efficiency of the device 1 .

[0116] The second electrode 5 comprises, forms or defines at least one plasmon ic structure or arrangement or lattice 11 (see, for example, Figures 1A and 1G) or a plurality of plasmonic structures or arrangements or lattices 11. The plasmonic structure 11 includes a plurality of optical nanoantennas and / or optically resonant structures 15. Each optical nanoantenna 15 or the optical nanoantennas 15 are configured to generate plasmons. The generation of plasmons is via interaction with the charge carriers provided or tunneled by the charge carrier tunnelling junction 7. This also results in light emission.

[0117] The optical nanoantennas 15 or the plurality of optical nanoantennas 15 are located on the charge carrier tunnelling junction 7 and extend on and / or across the charge carrier tunnelling junction 7.

[0118] The optical nanoantennas or optically resonant structures 15 of the plasmonic structure 11 may, for example be arranged non-periodically or disorderly arranged on the charge carrier tunnelling junction 7. The optical nanoantennas or optically resonant structures 15 of the plasmonic structure 11 may, for example be arranged periodically or orderly arranged on the charge carrier tunnelling junction 7.

[0119] The optical nanoantenna or optically resonant structure 15 can be, for example, formed or defined by a nano-line or nano-thread. The plasmonic structure 11 includes at least one or a plurality of nano-lines or nano-threads. The nano-line or nano-thread may be, for example, a nanowire or a nano-filament, ora nanostrip or a nanoribbon (see for example Figure 14A).

[0120] Figure 13 schematically shows non-limiting exemplary cross-sectional shapes of the optical nanoantenna or optically resonant structure 15. The cross-sectional shape or profile may be circular, rectangular, semi-circular (as observed in the TEM images of Figure 1 D), or polygonal.

[0121] The nano-line or nano-thread 15 may, for example, be characterized by or have an (high) aspect ratio in which its length is (significantly) greater (more than several hundred nanometer to micrometer scale) than its diameter (nanometer scale). For example, the length La may be between 10 (or 500) and 10000 times greater than a width Wa. For example, 4000 times for example for an exemplary length of La=400|j.m and an exemplary width Wa = 10Onm).

[0122] The length La is, for example, such that the optical nanoantenna 15 extends on the charge carrier tunnelling junction 7 and extends to a contact pad or zone CP to assure an electrical connection with the contact pad or zone CP of the device 1 (for example connected to ground in the schematic of Figure 1 A), and / or extends to define a sensing surface of the device 1.

[0123] The plasmonic structure or arrangement 11 (and the optical nanoantennas 15 thereof) defines or forms a surface, or metasurface, or plasmonic metasurface 21 that is, for example, a subwavelength structure provided or arranged on the charge carrier tunnelling junction 7 or on the two-dimensional plane (x-y directions) formed or defined by the charge carrier tunnelling junction 7.

[0124] The plasmonic structure or arrangement 11 (and the optical nanoantennas 15 thereof) supports plasmonic modes and is configured to generate surface plasmons by excitation by inelastic charge carrier (electron) tunneling, the carriers passing or tunneling through the junction 7 to the optical nanoantennas 15, with the subsequent emission of photons from the optical nanoantennas 15.

[0125] The plasmonic structure 11 (and the optical nanoantennas 15 thereof) may, for example, be configured to generate plasmons or plasmon resonances. The plasmonic structure or arrangement 11 (and the optical nanoantennas 15 thereof) may, for example, be configured to generate electromagnetically coupled plasmons or electromagnetically coupled plasmon resonances, or plasmonic lattice resonances or plasmonic surface lattice resonances.

[0126] The plasmonic structure 11 defines of forms an electric contact with the charge carrier tunnelling junction 7 and defines or forms an optical interface for light emission or electroluminescence light emission. Light emission and plasmon generation are produced by charge carriers provided by the charge carrier tunnelling junction 7 to the plasmonic structure 11.

[0127] The plasmonic structure 11 defines of forms the electrode 5 and electric contact with the charge carrier tunnelling junction 7 and defines or forms the optical interface for light emission or electroluminescence light emission. The plasmonic structure 11 defines or forms the electrode 5 to which the voltage potential difference is applied to generate charge carrier tunnelling.

[0128] The optical nanoantennas 15 or each optical nanoantenna 15 is an optically resonant nanoantenna supporting an optically resonant mode at an optical frequency or wavelength. For example, at a frequency in the frequency range 30GHz to 10OTHz or a wavelength in the wavelength range 300nm to 10|j.m, or for example, in the wavelength range 300nm to 2|j.m.

[0129] The optical nanoantennas 15 or each optical nanoantenna 15 has an optical sub-wavelength dimension or dimensions. The optical nanoantennas 15 or each optical nanoantenna 15 has sub-wavelength dimensions at a device operation wavelength or at a wavelength corresponding to a resonant mode frequency of the optical nanoantenna 15. The optical nanoantenna 15 may have a width Wa (y-direction) and / or a thickness (or height) Ha or ta (z-direction) that is sub-wavelength (see, for example, Figure 1H).

[0130] In an embodiment, the width Wa may, forexample, be largerthan the thickness ta. The optical nanoantenna 15 has a length La (x-direction) that is, for example, largerthan the width Wa and the thickness ta and the optical nanoantenna 15 is or forms an elongated nanoantenna 15. The length La may be significantly larger than the width Wa and the thickness ta, for example, several orders of magnitude greater, for example, between 10 to 10000 times greater. The optical nanoantenna 15 forms an elongated nanoantenna. The optical nanoantenna 15 extends in an elongated direction. The length La of the optical nanoantenna 15 extends in the elongated direction or elongated direction of extension of the optical nanoantenna 15. The width Wa of the optical nanoantenna 15 extends, for example, in a direction traverse or perpendicular to the elongated direction of extension of the optical nanoantenna 15. The thickness ta of the optical nanoantenna 15 extends, for example, in a direction traverse or perpendicular to the elongated direction of extension of the optical nanoantenna 15.

[0131] In the exemplary embodiment of the device 1 of which a portion of the plasmonic structure 11 is shown in Figure 3, the optical nanoantenna 15 has a thickness (or height) ta of (about) 50nm and a width Wa (Wx) of (about) 92.5nm, and a length La (Lx) of about 400 microns (see also the exemplary schematic of Figure 11).

[0132] Table 1 shows exemplary characteristic values of the plasmonic structure 11 and the optical nanoantenna 15 of one exemplary embodiment of the present disclosure for which TEM images are shown in Figure 1 D (see also the exemplary schematic of Figure 11). Element size Wx Width of the nanoantenna / nanowire 15 90nm-100 nm Wy Width of the y-axis interconnection / nanowire 25 90nm-100 nm Px Period of the x-axis nanoantenna / nanowire 15 400 nm

[0133] Py Period of the y-axis interconnection / nanowire 25 100 um

[0134] Lx Length of the x-axis nanoantenna / nanowire 15 400 um

[0135] Ly Length of the y-axis interconnection / nanowire 25 100 um HAu,t3 Height (thickness) of the nanoantenna / nanowire 15 45-50 nm HAd,t2 Height (thickness) of the adhesion layer 9 3-5 nm HA12O3,11 Height (thickness) of charge carrier tunnelling junction 7 5 nm

[0136]

[0137] HEI, 14 Height (thickness) of the first electrode 3 20-25 nm Table 1

[0138] The above values of Table 1 are exemplary, and a broad range of designs of the device 1 are possible, based on different values of device dimensions, including width, height, length, and periodicity of for example the structure 11 that are considered depending on the target application.

[0139] The nanoantennas 15 each include or define a sensing surface 17 of the plasmonic sensor device 1 . The sensing surfaces 17 are, for example, disposed or exposed to receive, directly or indirectly there upon, at least one of an entity, analyte and substance to be detected or sensed by the device 1.

[0140] Each sensing surface 17, or the sensing surfaces 17 are disposed on the plasmonic biosensor device (1) to receive,

[0141] The direct or indirect contact with or the direct or indirect reception of the at least one of the entity, analyte and substance on the sensing surface 17 wavelength shifts a luminesce emission spectrum of the plasmonic biosensor device 1 and / or augments in intensity the luminesce emission spectrum of the plasmonic biosensor device 1.

[0142] The plurality of optical nanoantennas 15 is located and extend on the charge carrier tunnelling junction 7 to present or provide the sensing surfaces 17 for contact with or reception of at least one of the entity, analyte and substance on the sensing surface 17 that wavelength shifts a luminesce emission spectrum and / or a spectral portion of the luminesce emission spectrum of the plasmonic biosensor device 1 and / or changes an intensity the luminesce emission spectrum of the plasmonic biosensor device 1 and / or changes an intensity of the spectral portion of the luminesce emission spectrum. The surfaces 17 are directly or indirectly exposed or presented so that, for example, the entity, analyte and / or substance can interact with the generated plasmons, plasmonic modes and / or plasmonic surface lattice resonances of the plasmonic structure 11 orthe nanoantenna mesh 11 and influence or impact the optical performance of the device 1 by wavelength shifting an emission wavelength (and / or a spectral portion thereof) of the analyte-free emission of the device 1 or bare-device emission, and / or by increasing / decreasing an emission wavelength intensity of the analyte-free emission of the device 1 or bare-device emission.

[0143] In the case of an indirect contact between the sensing surfaces 17 and at least one of the entity, analyte and substance, the intermediate material(s) and / or layer(s) define a separation distance between the sensing surfaces 17 and the at least one of the entity, analyte and substance that permits a wavelength shift a luminesce emission spectrum (and / or a spectral portion thereof) of the plasmonic biosensor device 1 and / or an augmentation / reduction in intensity the luminesce emission spectrum of the plasmonic biosensor device 1. This separation distance depends on the intermediate material or layer composition separating the sensing surfaces 17 and the at least one of the entity, analyte and substance, and can have, for example, a value less than or equal to 25nm (or less than or equal to about 25nm), preferably less than or equal to 10nm (or less than or equal to about 10nm), and most preferably less than or equal to 5nm (or less than or equal to about 5nm).

[0144] In an embodiment, at least some of the sensing surfaces 17 may, for example, be disposed or exposed to receive, directly there upon, at least one of an entity, analyte and substance to be detected or sensed by the device 1 ; and at least some of the sensing surfaces 17 may, for example, be disposed or exposed to receive, indirectly there upon, at least one of an entity, analyte and substance to be detected or sensed by the device 1.

[0145] In an embodiment, the first electrode 3, the charge carrier tunnelling junction 7 and the second electrode 5 form a multilayer device and / or form a superposed stacked layer device to define or form a planar device geometry (see, for example, Figure 1A and 1E). The charge carrier tunnelling junction 7 is or defines a planar tunnelling junction 7 extending in a plane or planar layer defined by the x-y directions, where a thickness of the junction 7 extends substantially perpendicularly to this plane in the z-direction. The first electrode 3 may also similarly extend to define a plane or planar layer. The charge carrier tunnelling junction 7 is superposed on the first electrode 3, and the plasmonic structure 11 is superposed on the charge carriertunnelling junction 7. The plurality of optical nanoantennas 15 is superposed on the planar tunnelling junction 7 to extend across the planar charge carrier tunnelling junction 7. The plasmonic structure 11 and the plurality of optical nanoantennas 15 form or define a light-emitting facet or interface that interfaces or attaches with at least one of an entity, analyte and substance to be detected or sensed by the device 1 .

[0146] The plasmonic structure 11 includes or forms at least one array PH, PV ora plurality of arrays PH, PV of optical nanoantennas 15.

[0147] In an embodiment, the plasmonic structure 11 includes or forms at least one array or stacked array 23 of optical nanoantennas 15 or a plurality of arrays 23 of optical nanoantennas 15 (see, for example, Figures 1 F, 1G, 11 and 11).

[0148] In an embodiment, the array 23 of optical nanoantennas 15 may, for example, comprise coextending optical nanoantennas 15 arranged or located side-by-side, each optical nanoantenna 15 being laterally displaced with respect to each other. The coextending optical nanoantennas 15 form a ladder rung layout arrangement. Each optical nanoantenna 15 is laterally displaced (in the y-direction) from an elongated direction of extension (x-direction) of the optical nanoantennas 15, as for example shown in the embodiment illustrated in Figure 1 F. The optical nanoantennas 15 may, for example, be laterally displaced in a direction nonparallel to the elongated direction of extension (x-direction) of the optical nanoantennas 15 or form a non-serial alignment of nanoantennas 15 in a direction non-parallel to the elongated direction of extension (x-direction) of the optical nanoantennas 15. The optical nanoantennas 15 form a non-linear series alignment of nanoantennas 15.

[0149] The optical nanoantennas 15 of the array 23 are, for example, separated or laterally separated by a distance sv. The distance sv is, for example, a sub-wavelength distance. The optical nanoantennas 15 of the array 23 may, for example, be (substantially) periodically disposed or located in a second direction (y-direction), with each optical nanoantenna 15 being located at a periodic interval distance Px. The periodic interval distance Px can be, for example, a subwavelength distance.

[0150] While the exemplary illustrated embodiment of Figure 1 F shows one array 23, the plasmonic structure 11 may include a plurality of arrays 23 of optical nanoantennas 15. Figure 11 illustrates an exemplary embodiment. The column arrangement of optical nanoantennas 15 of one array 23, PV is multiplied so that the plurality of arrays 23 comprises a plurality of such columns of optical nanoantennas 15. The arrays 23, PV may, for example, be (substantially) periodically disposed or located in a first direction (x-direction), with each array 23, PV being (substantially) periodically repeated by the periodic interval distance Py. The optical nanoantennas 15 of the array 23 may, for example, be (substantially) periodically disposed or located in the first direction (x-di recti on), with each optical nanoantenna 15 being located at the periodic interval distance Py. The periodic interval distance Py can be, for example, a subwavelength distance.

[0151] The periodic arrangement may, for example, be the same as that described further below in relation to the described embodiment comprising intersections 25, for which an exemplary illustration is provided in Figure 1 G and Figure 11 .

[0152] Each array 23 or the adjacent optical nanoantenna 15 of each array may be separated by a distance ss (see for example Figure 11), for example, a sub-wavelength distance. For example, a distance ss that is the same or substantially the same as the nanoantenna width Wa. The optical nanoantennas 15 can be, for example, disposed along the first direction (x-direction) and disposed (substantially) linearly to form a (substantially) linearly extending plurality, and are disposed along the second direction (y-direction) and disposed (substantially) linearly to form a (substantially) linearly extending plurality. The optical nanoantennas 15 may, alternatively or additionally, be disposed to extend in a curved manner to form a curved extending plurality.

[0153] The optical nanoantennas 15 are, for example, interconnected or electrically interconnected optical nanoantennas 15, or the plurality of optical nanoantennas 15 is a plurality of interconnected electrically interconnected optical nanoantennas. The interconnected optical nanoantennas 15 are, for example, directly interconnected nanoantennas 15 and / or physically interconnected nanoantennas 15 (see, for example, Figures 1A, 1C and 1G). The plasmonic structure 11 may include or form at least one array PH1 , PH2, PV1, PV2 ora plurality of arrays PH1 , PH2, PV1 , PV2 of optical nanoantennas 15 or of physically and / or electrically interconnected optical nanoantennas 15.

[0154] The plasmonic structure 11 may, for example, include at least one intersection or interconnection 25 (or a plurality of intersections 25) physically and / or electrically interconnecting optical nanoantennas 15. The interconnection(s) 25 interconnect the nanoantennas 15 to provides interconnected nanoantennas 15, and provide physically interconnected nanoantennas 15. The interconnections 25 allow to reduce emission discontinuities of the device 1 (see Figures 3a and 3b top-left panel). The emission discontinuities are considered to be the result of local defects which impact the tunnelling process of the charge carriers in the junction 7. Figure 3b shows the resulting reduced emission discontinuities of the device 1 compared to the plasmonic structure 11 of Figure 3a that does not include intersections 25.

[0155] The interconnection or interconnections 25 physically interconnect the nanoantennas 15 and may extend continuously to and / or between the nanoantennas 15 in the elongated direction of extension of the interconnection 25 and the nanoantenna 15. The interconnection or interconnections 25 and the nanoantennas 15 may comprise the same at least one metal that may extend continuously between the nanoantennas 15 and the interconnection or interconnections 25.

[0156] The interconnection or interconnections 25 physically interconnect the nanoantennas 15 to define or form a planer plasmonic structure 11 , superposed on the charge carrier tunnelling junction 7. The planer plasmonic structure 11 extends in a plane, located on the charge carrier tunnelling junction 7, that is parallel to the plane or plane of extension defined or formed by the charge carrier tunnelling junction 7, and / or the plane or plane of extension defined or formed by the first electrode 3.

[0157] The optical nanoantennas or nanowire 15 extending in a first direction (for example in a x-direction) functions as the optically resonant component to generate plasmons, with its resonance of gap plasmon or gap surface plasmon being tunable based on, for example, its width Wa, Wx. The interconnection or nanowire 25 that extends, for example, in a second or different direction (for example in a y-direction) serves or assures to electrically interconnect the structure 11 to assure a uniform electrical connectivity and / or a stable device performance across the device, and can assure a spatially homogeneous and / or electrically reliable light emission.

[0158] The intersection or interconnection 25 is an electrical structure or electrically resonant structure that electrically interconnects a plurality of optical nanoantennas 15. For example, Figure 11 schematically shows an exemplary embodiment including two electrical interconnections 25, each interconnecting a plurality of optical nanoantennas 15 (for example, each interconnecting the same plurality of optical nanoantennas 15).

[0159] The intersection or interconnection 25 may, for example, interconnect a plurality of optical nanoantennas 15 that extend in a first direction or are disposed along a first direction (x-direction) and / or a plurality of optical nanoantennas 15 that extend in a second direction (y-direction) different to the first direction (see, for example, Figures 11 and 1G where an interconnection 25 is located in the separation space or gap of the plasmonic structure 11 of Figure 11 having the separation distance ss). For example, at least a first optical nanoantenna 15a and a second optical nanoantenna 15b that extend in a first direction (x-direction) and / or a first and the second optical nanoantennas 15a, 15d that extend in a second direction (y-direction).

[0160] The intersection or interconnection 25, for example, fills the separation distance ss to provide a direct physical contact or connection between the first optical nanoantenna 15a and the second optical nanoantenna 15b in the first direction, and / or a direct physical contact or connection between the first and the second optical nanoantennas 15a, 15d in the second direction.

[0161] The plasmonic structure 11 may include, for example, a plurality of intersections (25a, 25b...) interconnecting or intersecting the plurality of optical nanoantennas 15. The plurality of optical nanoantennas 15 or optical nanoantennas 15 of the plurality of optical nanoantennas 15 may extend in a first direction or are disposed along a first direction and the plurality of intersections 25 may extend in a second direction different to the first direction.

[0162] The plasmonic structure 11 may include, for example, a plurality of optical nanoantennas 15 disposed or located along a first direction (x-direction) and a plurality of optical nanoantennas 15 disposed or located along a second direction (y-direction) different to the first direction. At least one or a plurality of intersections 25 extend to interconnect the plurality of optical nanoantennas 15 disposed or located along the first direction (x-direction) and extend to interconnect the plurality of optical nanoantennas 15 disposed or located along the second direction (x-direction).

[0163] The plasmonic structure 11 may include or form at least one array PH1 , PH2, PV1 , PV2 of physically interconnected optical nanoantennas (15), or a plurality of arrays PH1 , PH2, PV1 , PV2 of physically interconnected optical nanoantennas 15. For example, for illustration and explanatory purposes, Figure 1G includes a dashed box indicating the array PH1 including optical nanoantennas 15a, 15b interconnected by the intersection 25a and includes a dashed oval indicating the array PV1 including optical nanoantennas 15a, 15d also interconnected by the intersection 25a.

[0164] A plurality of intersections or interconnections 25 may electrically and physically interconnect the plurality of optical nanoantennas 15. The plurality of intersections or interconnections 25 may electrically and physically directly interconnect the plurality of optical nanoantennas 15 (see for example, Figures 1A, 1C, 1G, and 3). The plurality of optical nanoantennas 15 of the plasmonic structure 11 may, for example, be located to form a plurality of separated 1D arrangements or 1D arrays PH1, PH2 of optical nanoantennas 15 extending in a first direction (x-direction), and / or a plurality of separated 1D arrangements or 1D arrays PV1, PV2 of optical nanoantennas 15 extending in a second direction (y-direction) different to the first direction (see, for example Figure 1 G).

[0165] The separated intersections 25 may interconnect the optical nanoantennas 15 of the 1D arrangements or of the 1 D arrays PH1 , PH2 extending in the first direction, and interconnect the optical nanoantennas 15 of the 1D arrangements orofthe 1D arrays PV1, PV2 extending in the second direction.

[0166] While the plasmonic structure 11 is shown to include three optical nanoantennas 15 per array in the first direction (and three arrays PV1 ...PV3) and ten optical nanoantennas 15 per array in the second direction (and ten arrays PH1 ...PH10), this represents a non-limiting exemplary embodiment, and it is noted that the plasmonic structure 11 may include different quantities of nanoantennas 15 and / or arrays. The number of nanoantennas 15 and / or arrays can advantageously be large permitting to provide a large emission area and a large sensing or detection area increasing the reliability of detection / sensing measurements.

[0167] An optical nanoantenna 15 may, for example, be common to two different arrays. An optical nanoantenna 15 may, for example, be common to an array extending in the first direction and an array extending in the second direction. For example, in the illustrated embodiment of Figure 1G, the optical nanoantenna 15a is part the array PH1 extending in the first direction and the array PV1 extending in the second direction.

[0168] The plurality of intersections 25 and the plurality of nanoantennas 15 form or define a network of interlinked optical nanoantennas 15. The plurality of intersections 25 and the plurality of nanoantennas 15 (or arrays PH1 , PH2, PV1 , PV2 of nanoantennas) may form or define, for example, a mesh or mesh-like structure of interlinked optical nanoantennas 15. The interconnections 25 and the optical nanoantennas 15 comprise or are made of, for example, the same at least one metal.

[0169] The plasmonic structure 11 may include, for example, one or more closing or extremity intersections 25F located at an extremity of the plasmonic structure 11. The extremity intersection 25F extends, for example, to interconnect optical nanoantennas 15 located in or only in the direction of extension of the intersection 25 (the second direction or y-direction), or to interconnect optical nanoantennas 15 located at the outermost extremities of the plasmonic structure 11 .

[0170] The intersections 25 may, for example, have the same dimensions as the optical nanoantennas 15 and may comprise or be made of the same materials as the optical nanoantennas 15.

[0171] The physically interconnected optical nanoantennas 15 each comprise or is made of for example at least one metal, and the plurality of optical nanoantennas 15 are, for example, interconnected by at least one orthe plurality of interconnections 25 that comprise or are made of the same at least one metal.

[0172] The optical nanoantennas 15 extend, for example, in a first elongated direction and the plurality of interconnections 25 extend in a second elongated direction different to the first elongated direction. The second elongated direction is, for example, traverse to the first elongated direction. The length La of the optical nanoantenna 15, that for example extends in the first elongated direction, is greater than the width Wa of interconnection 25 that extends in a direction traverse or perpendicular to the first elongated direction.

[0173] The second electrode 5 forms the plasmonic structure 11 and the metasurface of the device 1 and thus forms both an electrical element and an optical element of the device 1.The second electrode 5 forming the plasmonic structure 11 , with physically and electrically interconnected optical nanoantennas 15, functions both electrically and optically.

[0174] The second electrode 5 functions as an electrical contact and the plasmonic structure 11 formed by the second electrode 5 also functions to assure the optical function of determining or controlling the emission or emission enhancement of the device 1 through the interconnected configuration of the plasmonic structure 11 , as well as defining the spectral content and a directivity of the device emission.

[0175] The second electrode 5 provides an electrical interconnection structured to form, forexmaple, a lattice such as a dual-directional lattice; and the structured electrical interconnection also influences the optical properties of the device by field localization enhancement and / or periodic lattice mode(s) provided via a periodicity of the plasmonic structure 11 provided by the structured electrical interconnection. The intersection 25 can be, for example, formed or defined by a nanowire or nano-filament or a nanostrip or a nanoribbon (see for example Figure 14A). The intersection 25 may, for example, comprise or form one or nano-antennas 29.

[0176] The number of optical nanoantennas 15 is, forexample, greaterthan the number intersections 25, forexample, at least 50, at least 100, at least 200 or at least 250 times greater.

[0177] Each optical nanoantenna 15 of the plurality of optical nanoantennas 15 can be disposed or located along the second direction (y-direction) is, for example, separated from a directly adjacent or neighboring optical nanoantenna 15 by a separation distance sv (see, forexample, Figure 1G). The separation distance sv is, forexample, a sub-wavelength separation distance. The separation distance sv is, for example, defined or set by the dimensions of the optical nanoantenna 15, for example, by the width or sub-wavelength width Wa, Wx of the optical nanoantenna 15. Each optical nanoantenna 15 of the plurality of optical nanoantennas 15 disposed or located along the first direction (x-direction) is, for example, separated from a directly adjacent or neighboring optical nanoantenna 15 by a separation distance sh (see, for example, Figure 1G). The separation distance sh is, for example, a sub-wavelength separation distance. The separation distance sh is, for example, defined or set by the dimensions of the intersection 25, forexample, by the width Wa, Wy of the intersection 25.

[0178] In an embodiment, the optical nanoantennas 15 of the plurality of optical nanoantennas can extend (substantially) periodically or doubly (substantially) periodically on the charge carrier tunnelling junction 7. The optical nanoantennas 15 can extend (substantially) periodically in a direction on the charge carrier tunnelling junction 7, or extend doubly (substantially) periodically in first and second directions on the charge carrier tunnelling junction 7. The optical nanoantennas 15 of the 1D arrangement or 1D array PH1, PH2 extending in the first direction can be (substantially) periodically located on charge carrier tunnelling junction 7, and / or the optical nanoantennas 15 of the 1D arrangement or 1D array PV1, PV2 extending in the second direction can be (substantially) periodically located on the charge carrier tunnelling junction 7.

[0179] A plurality of the optical nanoantennas 15 or each optical nanoantennas 15 of the plurality of optical nanoantennas 15 is forexample (substantially) periodically disposed or located along the first direction (x-direction) with a period Py, that is, periodically positioned or located to be recurring at a (substantially) regular interval with a repetition distance or period Py. In an embodiment, a plurality of the optical nanoantennas 15 or each optical nanoantenna 15 of the plurality of optical nanoantennas 15 is additionally or alternatively (substantially) periodically disposed or located along the second direction (y-direction) with a period Px, that is, (substantially) periodically positioned or located to be recurring at a (substantially) regular interval with a repetition distance or period Px.

[0180] The periodic value Px, Py may, for example, be sub-wavelength but not may also be larger in value. For example, periodic value may for example be in the range 10OOnm < Px < 1 mm, and 1000nm < Py < 1mm.

[0181] In an embodiment, optical nanoantennas 15 orthe optical nanoantennas 15 are (substantially) periodically disposed or located along the first direction (x-direction) with a period Py that is the same or substantially the same as the repetition distance or period Px of optical nanoantennas 15 or the optical nanoantennas 15 periodically disposed or located along the second direction (y-direction). A periodic separation distance Py of the optical nanoantennas 15 of the 1 D arrangement or 1 D array PH1 , PH2 extending in the first direction is substantially the same or substantially the same as the periodic separation distance Px of the optical nanoantennas 15 of the 1 D arrangement or 1 D array PV1 , PV2 extending in the second direction.

[0182] In an advantageous embodiment, optical nanoantennas 15 orthe optical nanoantennas 15 of the plurality of optical nanoantennas 15 periodically disposed or located along the first direction (x-direction) have a period Py that is different to the repetition distance or period Px of optical nanoantennas 15 or the optical nanoantennas 15 periodically disposed or located along the second direction (y-direction). The periodic repetition value Py is different to the periodic repetition value Px so that the plasmonic structure 11 comprises a (total) number of intersections 25 that provides an increased light emission intensity relative to or compared to a periodic repetition value Py that is the same as the periodic repetition value Px. Figure 3c shows exemplary measurement results of such an increased light emission intensity.

[0183] The optical nanoantennas 15 of the plurality of optical nanoantennas 15 may be periodically disposed along the first direction (x-direction) to have, for example, a period repetition distance Py that is greater than the repetition distance Px of the optical nanoantennas 15 periodically disposed along the second direction (y-direction). A periodic separation distance Py of the optical nanoantennas 15 of the 1 D arrangement or 1D array PH1 , PH2 extending in the first direction is greater the periodic separation distance Px of the optical nanoantennas 15 of the 1 D arrangement or 1D array PV1 , PV2 extending in the second direction. The optical nanoantennas 15 of the plurality of optical nanoantennas 15 can be periodically disposed along the first direction (x-direction) to have, for example, a period repetition distance Py that is between 10 and 5000 times greater, or between 10 and 10000 times greater (the indicated values included) than the repetition distance Px of the optical nanoantennas 15 periodically disposed or located along the second direction (y-direction).

[0184] In an embodiment, the optical nanoantennas 15 of the plurality of optical nanoantennas 15 can be periodically disposed along the first direction (x-direction) to have, for example, a period repetition distance Py that is (i) greater than the repetition distance Px of the optical nanoantennas 15 periodically disposed along the second direction (y-direction) and (ii) that varies or changes. For example, this may provide a plurality of sets of periodic optical nanoantennas 15 where each set has a set period that is different. The repetition distance Px of the optical nanoantennas 15 periodically disposed along the second direction (y-direction) is fixed or remains fixed. The periodic separation distance Py of the optical nanoantennas 15 of the 1 D arrangement or 1 D array PH1 , PH2 extending in the first direction changes value to define, for example, a plurality of sets of periodic optical nanoantennas 15 having a set period that is different.

[0185] The separated 1D arrangements or 1 D arrays of optical nanoantennas 15 may be periodically separated on the charge carrier tunnelling junction 7. The separated 1 D arrangements or 1 D arrays PH1 , PH2 of optical nanoantennas 15 that each extend in the first direction may be periodically separated, for example, by the periodic separation distance Px. The separated 1 D arrangements or 1D arrays PV1 , PV2 of optical nanoantennas 15 that each extend in the second direction may be periodically separated, for example, by the periodic separation distance Py. The periodic layout of the periodic separation distances Px, Py previously described above in relation to the optical nanoantennas 15 equally applies to these arrangements or arrays of optical nanoantennas 15.

[0186] In an exemplary embodiment, the optical nanoantennas 15 may be arranged in for example at least two directions or orthogonal directions, each direction having a differing periodicity to generate a plasmonic lattice mode across the charge carrier tunnelling junction 7 (see, for example, Figure 1 G).

[0187] Similarly, the separated intersections 25 can be periodically separated on the charge carrier tunnelling junction 7. The separated intersections 25 are periodically separated, for example, by the periodic separation distance Py. The periodic layout of the periodic separation distances Px previously described above in relation to the optical nanoantennas 15 equally applies to the separated intersections 25. The origin of the emission enhancement of the device 1 is procured by the interconnected plasmonic structure 11 and comprises an optical enhancement due to the dispersive plasmon ic lattice mode resonances and / or non-dispersive gap modes supported in particular by the periodically structured metasurface formed by plasmonic structure 11. This determines the emission wavelength / frequency peak and can also determine the emission directivity of the device 1 . The plasmonic structure 11 allows to provide or engineer plasmonic modes or lattice modes through the metasurface design to control the emission intensity and also emission wavelength and directivity.

[0188] The interconnected optical nanoantennas 15 of the plasmonic structure 11 provides an enhanced refractive index sensitivity permitting to provide a device 1 of higher sensitivity to detection of an entity, analyte or substance. The plasmonic structure 11 having different periodicities improves uniformity / signal strength. Bidirectional lattice coupling assures better mode confinement I surface coverage. As previously mentioned, the doubly periodic optical nanoantennas 15 advantageously further improve light emission uniformity over large areas of the device 1.

[0189] The Inventors have to date found that the geometrical parameters of the plasmonic structure 11 that individually and collectively impact the most the light emission characteristics of the device 1 are the optical nanoantennas or nanowire width Wa,Wx, the period Px of the optical nanoantennas or nanowire 15 in the first direction (or x-direction), the thickness HAu,t3 of the optical nanoantennas or nanowire 15 and the thickness HAi2O3, t1 of the charge carrier tunnelling junction 7.

[0190] The optical nanoantennas or nanowire width Wa,Wx may for example be 50nm < Wa,Wx < 550nm, or 50nm < Wa,Wx < 150nm. The width Wy of the intersection 25 can be identical to optical nanoantennas or nanowire width Wa,Wx, that is 50nm < Wa,Wy < 550nm, or 50nm < Wa,Wy < 150nm.

[0191] The period Px of the optical nanoantennas or nanowire 15 may for example be 350nm < Px < 800nm.

[0192] The separation distance sv separating directly adjacent or neighboring optical nanoantennas or nanowires 15 may for example be 10Onm < sv < 400nm. The thickness HAu,t3 of the optical nanoantennas or nanowire 15 may for example be 30nm < HAu,t3 < 70nm.

[0193] The thickness HA|2o3, t1 of the charge carrier tunnelling junction 7 may for example be 1nm < HAi2O3, t1 < 20 nm.

[0194] In one exemplary embodiment the plasmonic structure 11 and the plurality of optical nanoantennas 15 are configured to generate plasmons or plasmonic surface lattice resonances providing electric field localization and enhancement at a sensing surface of the plasmonic structure 11 and the optical nanoantennas 15. The exemplary embodiment provides a lattice resonance characterized by field enhancement at the top of the antenna 15 and to optimize or favor enhanced biosensing performance of the device 1 .

[0195] The plasmonic metasurface, being a periodic structure with TM-polarized resonances, underwent an angular resolution investigation of its optical response (reflectance) to obtain a deeper understanding of the metasurface modes. Figures 12A and 12B present numerically modeled angle-resolved reflectance spectra with varying geometrical parameters. The fall in the reflection corresponds to the absorption of the incident light. Due to the reciprocity theorem, electrically generated plasmons through electron tunneling have to illuminate through the same states as absorption of the incident light. Attention is paid in particular to the absorption on angle- resolved reflection spectra to further detect the light, generated by electrically-driven plasmons. The mesh structures 11 were analyzed based on the following geometrical parameters: nanowire width (Wx), period of the x-direction long nanowire (Px), nanowire thickness t3 (HAu), and barrier thickness (HAi2os). Other parameters, such as the bottom contact thickness t4 and adhesion layer thickness t2, seem to have a minimal impact on the optical response under the given polarization.

[0196] The angle-resolved reflection spectra in Figures 12A and 12B illustrate the influence of these parameters on the optical resonances. These Figures reveal an angular-dependent lattice resonance occurring between 500-900 nm and a broad gap plasmon resonance around 1200 nm, which spans a range of incident angles.

[0197] In one example embodiment (design 1), the lattice resonance, characterized by field enhancement at the top of the antenna 15, was optimized for enhanced biosensing performance. Preferred device design values were determined to be:

[0198] 90nm < Wa,Wx,Wy < 110nm, or 90nm < Wa,Wx,Wy < 100nm 350nm < Px < 450nm

[0199] 40nm < HAu,t3 < 60nm, and / or

[0200] 3nm < HAI2O3, t1 < 8nm

[0201] A more preferred device design was determined to be: Wx, Wy, Wa = (about) 90nm or (about) 100 nm, Px = (about) 400 nm, HAut3 = (about) 50 nm, and / or t1, HA|2o3 = (about) 5 nm.

[0202] In another exemplary embodiment, the plasmonic structure 11 and the plurality of optical nanoantennas 15 are configured to generate counter-propagating plasmonic lattice modes in the plasmonic structure 11 to provide an optical band gap in a spectral region of the electroluminescence of the plasmonic biosensor device 1. This advantageously can assure enhanced sensing capability, and / or a sharper spectral edge, and / or a higher collection efficiency.

[0203] Figure 16 shows an alternative or improved electroluminescence (EL) and biosensing performance of a device 1 of the present disclosure. This embodiment exploits the use of the interaction between counter-propagating lattice modes to get mostly pronounced resonances.

[0204] This is achieved by a design (design 2) in which:

[0205] 450nm < Wa,Wx,Wy < 550nm, and / or

[0206] 600nm < Px < 750nm.

[0207] The adhesion layer 9 may optionally have a thickness t2 where 1 nm < t2 < 3nm, or 1 nm < t2 < 2nm.

[0208] A more preferred device design was determined to be: Wx, Wy, Wa = (about) 480nm, Px = (about) 680 nm and optionally, t2 = (about) 1 nm or 2 nm.

[0209] The separation distance sv separating directly adjacent or neighboring optical nanoantennas or nanowires 15 may for example be 150nm < sv < 250nm, or 175nm < sv < 225nm, for example about 200nm.

[0210] The device 1 may have the same exemplary values for the other parameters set out in Table 1 above, such parameters being exemplary and being capable of being varied without a significant impact on the advantages of the present exemplary embodiment. The atomic force microscopy (AFM) images of fabricated samples having the design of the previously described exemplary embodiment (design 1) and the above design (design 2) are shown in Figures 16a and 16b. For the design 2 instead of just lattice resonances of the previous design 1 shown in Figure 16c, one obtains a highly absorptive lattice mode with the “prohibited” band (anticrossing region) in the spectral region of the tunneling EL in the design 2 (Figures 16d to 16e). This “prohibited” band or optical band gap originates from destructive and constructive interference of two counterpropagating lattice modes. Design 2 provides an optical band gap of the plasmonic lattice mode in the spectral region of the EL or tunnelling EL. The most efficient energy transfer from plasmon to photon can be provided by the constructive interference mode having the highest absorption. The value of the band splitting, absorption strength, resonance spectral linewidth, and other parameters can be accurately tuned by the structure 11 design. This advantageously also provides steep slope fall in the experimentally measured EL intensity, particularly useful for the efficient signal probing in the self-illuminating biosensor.

[0211] This embodiment, as seen in Figures 16c to 16e and in Figure 17, exhibits a sharper spectral edge. This improvement is primarily due to the strong resonance with the "prohibited" band (anticrossing region) of the structure 11 of this embodiment, which more effectively blocks the emission at the short-wavelengths making the optical resonance in EL spectra much more pronounced, as shown in the experimentally measured EL spectra in Figure 16e. Since the resonance has a sharp left-arm slope, the spectral shift (due to some analyte) can be better detected in the given spectral range (of the left arm slope) as a ratio of pristine and shifted EL.

[0212] This embodiment can also assure a higher collection efficiency with a narrow angle emission. As illustrated in Figure 18, the design 2 significantly improves efficiency of light detection by narrowing the emission angle. Design 1 has a wider-angle emission, which caused light to illuminate at large angles which can reduce the overall light collection efficiency. In comparison, design 2 incorporates optimized structures and electrode configurations that directs light from the generated plasmons into a more confined emission angle. This allows using a low or lower numerical aperture objective and collecting more light coming from the highly sensitive plasmonic lattice mode, cutting the scattered and poorly sensitive light. This approach also permits to improve the signal-to-noise ratio and, therefore, overall performance. The experimental results of the EL spectra from design 1 and design 2 are shown in Figures 18c and 18f. The focused, narrow-angle emission greatly enhances collection efficiency, making the system more effective in low-light conditions. This embodiment can also assure a higher sensitivity. Both the aforementioned features of the sharp spectral edge and narrowing angle emission enhance the overall sensing performance. To compare the design 1 and design 2, a thin film (~35 nm) of D-Alanine was deposited on top of the structure 11. Due to the high refractive index lattice modes of both designs there is a shift to the red wavelength region as seen in the measured angle-resolved reflection spectra (Figs. 18a to 18b and 18d to 18e). Due to the mentioned features of the design 2, instead of just an increase in the overall intensity of EL as in design 1 (Figure 18c), design 2 has obvious changes in the EL spectral response (Figure 18f). In the chosen exemplary spectral range (for example 700-800nm) it can increase the EL intensity ratio to 10, whereas the design 1 , in the same conditions, gives a ratio of around 2.2. This difference is due to the mentioned origin of the designed optical band gap of the plasmonic lattice mode and usage of the low numerical aperture objective (04x N.A. = 0.13).

[0213] Design 2 is capable of detecting even lower concentrations of analytes. This was verified by an experiment involving the spotting of different concentrations of antibodies IgG (Figure 19). The antibodies were dissolved in BSA, spotted by the spotting machine cellenion, after the drops with analyte stayed for 2 hours to let the antibodies stick to the device surface, and in the end, the devices were dripped in the deionized water to clean it from the BSA. The EL spectra were measured before and after the spotting for each pad. The preliminary results of the experiment are shown in Figure 19. To better see the difference between the responses, the difference between “pristine” and “spotted” spectra was determined and divided by the “pristine” EL spectra (lower panels in Figure 19). As one can see, the design 2 is capable of detecting an amount of analyte as small as 70 molecules per |j.m2(ratio reaches 0.2 for the particular spectral range). Although, a preliminary result, it brings significant promise for a device with good detection limits.

[0214] The plasmonic structure 11 may, for example, include cavities or separation cavities 27. The separation cavity 27 is located between two optical nanoantennas 15 or between first and second optical nanoantennas 15. For example, in the illustrated exemplary embodiment of Figure 1 G, a separation cavity 27 is located between the first optical nanoantenna 15a and the second optical nanoantenna 15b. The optical nanoantennas 15 may define or form the cavity 27. A base of the separation cavity 27 may, for example, be formed by the junction 7. The separation cavity 27 may include or be (partially) filled with a material different to that of the optical nanoantenna. The plasmonic structure 11 may include or form at least one network of interlinked optical nanoantennas 15 and separation cavities 27, where the separation cavity 27 is located between optical nanoantennas 15 of the network.

[0215] The plasmonic structure 11 may also include a plurality of openings located between the optical nanoantennas 15 and permitting access to the separation cavities 27. The plurality of optical nanoantennas 15 may delimit a plurality of openings located between the optical nanoantennas 15.

[0216] The separation cavity 27 and / or the opening can be, for example, located or formed between first and second optical nanoantennas 15 and a first and / or second separated intersection 25.

[0217] The separation cavity 27 and / or an opening are configured to receive or hold at least one of an entity, analyte or substance 33 to be detected by the device 1.

[0218] As mentioned, the optical nanoantennas or optically resonant structures 15 of the plasmonic structure 11 may, for example be arranged non-periodically or disorderly arranged on the charge carrier tunnelling junction 7. The optical nanoantennas or optically resonant structures 15 of the plasmonic structure 11 may, for example be arranged periodically or orderly arranged on the charge carrier tunnelling junction 7.

[0219] In an exemplary embodiment, the optical nanoantennas or resonant structures 15 may comprise or be O-dimensional resonant structures instead or in addition to the nano-wires 15 as shown in the embodiments illustrated in Figure 1A and in Figure 14A . As shown in Figure 14C, the optical nanoantennas or resonant structures 15 may, for example, comprise or consist of nanorods or elongated nanorods and / or of bow-tie shaped structures that are provided on the charge carrier tunnelling junction 7.

[0220] These structures 15 function independently as optical resonators and electrical connectivity can be provided by the electrical intersections 25.

[0221] Concerning the arrangement of the resonator 15 on the insulator layer, the resonators 15 (whether O-dimensional or 1 -dimensional) can be arranged either randomly or in an ordered manner, as previously mentioned.

[0222] In the case of a random arrangement, a bottom-up approach can be utilized, which involves dispersing liquid samples containing chemically synthesized nanosized plasmonic resonators 15. For example, self-assembled monolayers (SAMs, molecules) can link plasmonic nanostructures 15 to the insulating layer 7 through chemical bonding or physically just attached to the insulator 7. When employing randomly arranged resonant structures 15 on the insulator layer, physical and electrical interconnection via interconnections 25 is included.

[0223] If the resonators are arranged in an ordered manner, a top-down approach, such as lithographically defined patterns, can be employed. The top-down approach is more suitable for large-scale production, provided that the lithography techniques can support such fabrication. If the resonators 15 are prepared using lithography and include electrical connections, they can function effectively for light emission devices. If the lithographically prepared resonators 15 still require additional electrical connections when they are 0-dimentional, the same strategy can be considered to connect all arranged resonators 15 with interconnections 25.

[0224] The device 1 can be configured to provide emitted electroluminescent light through or out of the support or substrate 19, or through or out of a device back-side located opposite the plasmonic structure 11 side that receives a species, entity, analyte or substance 33 to be analyzed or detected. This allows the device 1 to have a sensing side and a collection side that are located opposite to each other on the device. The support or substrate 19 can be for example comprise or consist of an optically transparent material that is transparent at the operation wavelength or wavelengths of the device 1.

[0225] The first or bottom electrode 3 may comprise or consist of material that is transparent at the operation wavelength or wavelengths of the device 1 , such as, ITO, IGZO, or ITZO. The first or bottom electrode 3 may alternatively or additionally include structuring or patterning in or on the bottom electrode layer 3 and configured to direct light emission out through the back side BCS. Alternatively, or additionally the first or bottom electrode 3 can have a thickness t4 that is takes into consideration the material’s penetration depth to permit sufficient light emission intensity to pass through the first electrode 3 and out through the back side BCS. These features can redirect a sufficient amount of light to the backside BCS of the device 1. This allows to separate the top surface of the device 1 for sensing and the bottom surface for optical detection (collection), as shown in Figure 20c, which is highly beneficial for device miniaturization and reducing background noise.

[0226] The measured light emission, shown for example in Figures 3 and 5, is directed mostly to the top side of the device 1 in the fabricated device 1 and collected also from the top side of the device 1. When the device has a relatively large emission angle, this necessitates high NA objective lens to efficiently collect the generated light from the top of the device, as schematically shown in Figure 20a. Designs that using the same mesh structure 11 but with different nanostructure dimensions assure light emission in a narrower angle. This allows to collect more light and also to use a lower NA objective lens (Figure 20b). Such designs are promising for practical applications because light collection is easier and there is also an increased level of collected light and thus an increased collection efficiency.

[0227] There is flexibility for controlling the emission direction in specific directions and optimizing the collection efficiency based on designs of the device 1 having different values of device dimensions, including for example width, height, length, and periodicity of for example the structure 11 .

[0228] The light leakage was also measured from the backside of the chip or substrate 19, as shown in Figure 20C and Figure 21 B. The signal obtained was relatively weak due to scattered light reaching the backside and being captured by the objective lens. This is primarily because the first electrode 3 in the fabricated device has a uniform aluminum film that strongly blocks light, given the small penetration depth in the visible spectral range for aluminium (<15 nm at a 650 nm wavelength). Nevertheless, Figure 21 B makes it clear that light emission can be collected from the backside BCS of the device 1 , and the device 1 can have a sensing side FSS and a collection side BCS that are located opposite to each other on the device 1. The inclusion of a first electrode 3 having the above stated characteristics allows to improve the quantity of light collected from the backside BCS of the device 1.

[0229] Additionally, by dedicating the top surface for sensing and the bottom surface for optical detection, the previously described second design minimizes cross-interference between the optical and sensing sides. This configuration results in a more efficient separation of signal and noise, leading to higher detection sensitivity and incorporation of a sharper spectral edge to reduce noise from unwanted wavelength range, and a higher collection efficiency design for ensuring more light capture.

[0230] Another aspect of the present disclosure concerns a sensor system or point-of-care device 100 including at least one plasmonic sensor device 1 (see, for example, Figure 10). The sensor system or point-of-care device 1 may include, for example, at least one spectrometer and / or an optical detector (for example, a pixelated camera) or photodetector 102 for receiving light emission from the plasmonic sensor device 1 (from the front side FSS or the backside BCS, (see Figure 20c)). A lens (not shown) may optionally be included to direct the emitted light to the spectrometer and / or optical detector 102. The spectrometer and / or optical detector 102 is configured to determine emission light spectra and to provide or communicate the emission light spectra for further analysis, for example, as a emission light spectrum electronic signal or emission light spectra data. The system 100 may also include at least one data processing device 104. The data processing device 104 operatively connected to the spectrometer and / or optical detector 102 to receive the emission light spectrum data or signal.

[0231] The data processing device 104 may include at least one processor 106 and may include at least one storage or memory device 108. The data processing device 104 processes information that may be transmitted from, without limitation, the spectrometer and / or optical detector 102 to which the data processing device is operatively coupled for communication therebetween, or in operative connection thereto.

[0232] The data processing device 104 may, for example, be in operative connection with a display device of the system 1 for displaying calculation or analysis results. The data processing device 104 may, for example, be configured to communicate calculation or analysis results to external devices with which the data processing device is operatively coupled for communication and / or in operative connection.

[0233] Intra-device communication, such as communication may for example be via a wired (for example wired electronic circuitry) and / or a wireless communication technology.

[0234] The processor may comprise one or more processors or microprocessors or processing devices, or microcontrollers, microcomputers, programmable logic controllers (PLC), or application specific integrated circuits, and other programmable circuits.

[0235] Each “processor” herein includes processing circuitry, and / or may include multiple processors. For example, as used herein, including the claims, the term “processor” may include various processing circuitry, including at least one processor, wherein one or more of at least one processor, individually and / or collectively in a distributed manner, may be configured to perform various functions described herein. As used herein, when “a processor”, “at least one processor”, and “one or more processors” are described as being configured to perform numerous functions, these terms cover situations, for example and without limitation, in which one processor performs some of recited functions and another processors) performs other of recited functions, and also situations in which a single processor may perform all recited functions. Additionally, the at least one processor may include a combination of processors performing various of the recited / disclosed functions, e.g., in a distributed manner. At least one processor may execute program instructions to achieve or perform various functions. The storage or memory device 108 may, for example, comprise a computer-readable medium or computer-readable memory for example a semiconductor memory, or a non-volatile medium or memory such as flash memory; or comprise for example a hard disk drive HDD. The storage or memory device may be removable or non-removable. The computer-readable medium or memory is, for example, a non-transitory computer-readable medium or memory.

[0236] The storage or memory device stores and transfers information and instructions to be executed by processing device 104. The memory or storage device can also be used to store and provide temporary variables, static information and instructions, or other intermediate information to the data processing device during execution of instructions by the data processing device 104.

[0237] Instructions that are executed include, but are not limited to, instructions for analysis of received signals and data or of transmitted signals or data transmitted from the spectrometer and / or an optical detector. The execution of sequences of instructions is not limited to any specific combination of hardware circuitry and software instructions.

[0238] Instructions may, for example, include instructions or computer instructions executable on the processor or data processor. Instructions may, for example, be in the form of processor or computer instruction code.

[0239] The storage or memory device 108 may include, for example, one or more computer programs 110 comprising instructions permitting to manage and operate the calculations relating to the optical spectra and the analysis of the optical spectra mentioned herein.

[0240] For example, custom-made (for example, Matlab) functions may be used for such calculations and analysis.

[0241] In an embodiment, the plasmonic sensor device 1 is located on a mounting device to be angularly orientated with respect to the optical detector 102 to provide a selected angular range and a selective spectral range of the light emission to the at least one spectrometer and / or optical detector 102. In this embodiment, the sensor system or point-of-care device 1 can be spectrometer-free and only comprise the optical detector 102 and not an optical detector - spectrometer combination.

[0242] Another aspect of the present disclosure concerns a sensing or detection method. The method includes providing at least one plasmonic sensor device 1 or sensor system 100 including at least one plasmonic sensor device 1, providing at least one sample for analysis or investigation to the plasmonic sensor device 1 or to the plasmonic structure 11 thereof (for example, into cavities 27); and generating light emission by the plasmonic sensor device 1.

[0243] The method may include measuring the generated light emission to determine a wavelength shift in a luminesce emission spectrum and / or in or of at least one spectral portion of the generated luminesce emission spectrum; and / or a change (for example, an augmentation or reduction) in intensity of the luminesce emission spectrum and / or a change in intensity in at least one spectral portion of the generated luminesce emission spectrum. This determination can be made with respect to a bare plasmonic sensor device 1 without a species, entity, analyte or substance 33 that is to be investigated, or with respect to a reference plasmonic sensor device 1 including at least one species, entity, analyte or substance 33.

[0244] For example, the sensing surface or surfaces 17 receiving at least one of an entity, analyte and substance may wavelength shift a luminesce emission spectrum of the plasmonic biosensor device and / or at least one spectral portion of the generated luminesce emission spectrum to a longer wavelength and augment in intensity the luminesce emission spectrum of the plasmonic biosensor device. Compared to a bare device 1 , the presence of the entity, analyte and substance may produce a red wavelength-shift and an increase in emitted light intensity.

[0245] The species, entity, analyte or substance 33 interacts with plasmonic modes of the nanoantenna arrangement or mesh 11 to influence the optical performance of the device 1, for example to change the sensor device 1 readout.

[0246] Light emission is, for example, generated by the plasmonic sensor device 1 prior to providing the sample for analysis or investigation to the plasmonic sensor device 1, and light emission received from the plasmonic sensor device 1 at the spectrometer and / or optical detector is used to determine a reference measurement. Light emission is received or provided to the spectrometer and / or optical detector when the sample is provided for analysis is used to determine a sample measurement. The presence of at least one of a species, entity, analyte or substance 33 based on a comparison of the sample measurement and the reference measurement is then determined or carried out. Light emission may be received from the plasmonic sensor device 1 from the front side FSS and / or the backside BCS of the device 1 . Sensing or detection can be determined by a wavelength shift and / or by a change in emission intensity.

[0247] The generated light emission can be measured to determine a wavelength shift of at least one spectral portion of the generated luminesce emission spectrum of the plasmonic biosensor device 1 when the sample for analysis or investigation is provided compared to prior to the provision of the at least one sample for analysis or investigation. The generated light emission can, for example, be measured to determine a wavelength shift of the plasmonic spectral feature SC of the generated luminesce emission spectrum. The wavelength shift can be determined at the wavelengthrefi (or reference wavelengthrefi) in the spectral range of the plasmonic spectral feature.

[0248] Additionally or alternatively, the generated light emission can be measured to determine a change in light intensity of the spectral portion of the generated luminesce emission spectrum when the at least one sample for analysis or investigation is provided compared to prior to the provision of the at least one sample for analysis or investigation. The change in light intensity of the plasmonic spectral feature SC can be determined to determine the presence of a species, entity, analyte or substance 33. The change in light intensity can be determined at the wavelength / .ref (or reference wavelengthrefi) in the spectral range of the plasmonic spectral feature SC.

[0249] As previously mentioned, the wavelengthrefi may be at an emission intensity peak value PK1 or at least one emission intensity peak value PK1 of the plasmonic spectral feature SC.

[0250] Additionally or alternatively, the generated light emission can be measured to determine the change in light intensity in a wavelength window or rangewindow of the plasmonic spectral feature (see for example, Figure 5e). The change in light intensity in the wavelength window or rangewindow may comprise determining or calculating at least a differential between (i) light intensity in the wavelength window or rangewindow when the sample (species, entity, analyte or substance 33) for analysis or investigation is provided and (ii) light intensity in the wavelength window or rangewindow priorto the provision ofthe sample (species, entity, analyte or substance 33) for analysis or investigation. An average value can for example determined by averaging the determined differential over wavelength values of the wavelength window or range / .window. Further exemplary details of exemplary specific embodiments and measurements obtained therefrom of the device 1 of the present disclosure are now set out below.

[0251] As is evident from the above description, the present disclosure concerns, for example, a plasmonic sensor 1 with an embedded source of light provided by quantum tunnel junctions 7. An optically resonant, doubly periodic nanowire metasurface 21 serves as a top contact for the junction 7 and provides extremely uniform emission over large areas, amplified by nanoantenna modes that simultaneously enhance the spectral and refractive-index sensitivity. Spatially resolved refractometric sensing of nanometer-thick polymer coating and protein layer is demonstrated below. The device 1 of the present disclosure opens exciting prospects based on a disruptive platform for integrated electro-optical biosensors.

[0252] The present disclosure presents and demonstrates an exemplary device 1 that is an on-chip self-illuminating label-free optical biosensor 1 that exploits quantum tunneling in a multilayer metal-insulator-metal film. The top surface incorporates a plasmonic metasurface 21 that plays a dual role, serving simultaneously as an electric contact for the tunnel junction 7 and as an optical interface for facilitating the coupling of quantum electron tunneling emission to free space light modes. The latter aspect, which is enabled by the localized plasmonic modes and / or the generation / excitation of surface plasmons and / or the generation / excitation of surface plasmon resonances (for example, localized surface plasmons or surface plasmon polaritons) of the antennas 15 in the metasurface 21 , impacts the internal quantum efficiency of the tunneling process through the enhancement of the electromagnetic density of optical states, contributing to the improvement of radiative quantum efficiency and, therefore, enhancing the detected signal. A flexible metasurface design is exploited to optimize for biosensing to produce efficient and spatially uniform LIET, enabling the mapping of the spatial distribution of the analyte layer 33 deposited on the metasurface 21 . These features ultimately enable an integrated nanoscale light source that can transduce small changes of the local optical environment from the low volumes of analyte 33 to the modulation ofthe far field signal without requiring labels.

[0253] The biosensor 1 is tested with various analytes 33 such as thin layers of polymer and protein, and it is observed that both the intensity and the spectral profile of the emitted light are modulated upon local refractive index changes produced by the presence of the analyte 33. These results support the use of LIET devices 1 as highly compact and sensitive on-chip optical biosensors for point-of-care POC applications by eliminating the need for an external light source. Different self-illuminating metasurface 21 designs were explored. The metasurface 21 can, for example, be considered to be based on an interconnected mesh of nanowire nanoantennas 15 that are used as a transducer between the plasmons excited by inelastic electron tunneling in a vertical planar junction 9 and the far-field light emission (Fig. 1 A). In the schematic partial cross-sectional view of the device (Fig. 1A, inset), these cross-linked gold nanowires 15 reside on top of a thin alumina layer (the tunneling barrier 7) that separates it from an Al film (the bottom contact 3).

[0254] To make this barrier 7 extremely uniform and ensure a low defect density, thermal oxidation of an amorphous Al film 3 sputtered on a glass substrate 19 is used, which leads to the formation of a thin AI2O3film with self-limited thickness. The metasurface 21 is fabricated by depositing a 50 nm thick gold film after a thin (about 5 nm) chromium adhesion layer 9. The nanowires have a width of about 92.5 nm (from scanning electron microscopy (SEM) images), a fixed period of 400 nm along the x-axis, as shown in Fig. 1A and a varying period (100pm to no period) along the y-axis.

[0255] A schematic of the resulting tunnel junction 7 is shown in Fig. 1 B. In the experiments, a positive bias voltage Vbis applied to the gold metasurface layer 21 while the aluminum layer 3 is grounded. Inelastic electron tunneling leads to the excitation or generation of plasmons and subsequent emission of photons that are detected in the far field with a spectrometer system forspectral analysis orwith a camera for imaging. To electrically drive the sensor 1 , a custom-printed circuit board is used with a set of contact pads (Fig. 1 D) that are connected to the pads on the chip via wire bonding. The contact pad of each device is fabricated on top of the bare glass area, while the metasurface 21 extends overthe bottom Al contact (Fig. 1 D(ii)).

[0256] The transmission electron microscopy (TEM) image of a thin lamella cut from the metasurface in Fig. 1 D(iii) demonstrates a high-quality tunneling contact with a AI2O3barrier thickness of 5 nm.

[0257] The metasurface electro-optical properties were examined. An important prerequisite for sensing applications is to realize a LIET device 1 that produces highly uniform emission over a large detection area for reliable measurements. Due to the extreme sensitivity of the tunnel junction to local defects, even minor perturbations along the length of the antennas 15 could lead to voltage drops and strong variations in the emission strength. To illustrate this point, Fig. 3a presents a metasurface 21 made solely from a 1D array of horizontal nanowire antennas 15 with a period of 400 nm. Its LIET image clearly shows such defect-related emission discontinuities. This issue is mitigated by adding an array of nanowires 15 in the y- axis direction to form an interconnected mesh (see SEM images in Figs. 3b, 3c). Overall, one observes that the doubly periodic design suppresses discontinuities, but the density of the interconnections also affects the strength of the emission intensity.

[0258] For example, the LIET image of a high-density mesh with 2D arrays of nanowires 15 having a period of 400 nm in both vertical and horizontal directions (in Fig. 3b) produces a very low emission yield. Instead, Fig. 3c shows an optimized metasurface 21 with an exemplary period of 400 nm and 100 pm in the x- and y-axis directions, respectively. This design principle with less dense interconnections produces a highly uniform emission over a large area without sacrificing the emission intensity, a result of a favorable tradeoff between the electrical connectivity that improves with a denser mesh and far-field light outcoupling that is facilitated by sparser antennas.

[0259] Insets in Fig. 3c are the back focal plane images of the emission collected from the metasurface fortwo orthogonal polarizations of the analyzer. The radiation patterns show two characteristic lobes that reveal the dipolar nature of the emission associated with the transversal plasmonic mode of the nanowire grid 21. The weaker signal with a similar pattern observed for the opposite polarization is consistent with the smaller density of nanowire antennas 15 in the orthogonal direction.

[0260] Further characterization of the exemplary optimized metasurface 21 through electro-optical measurements was carried out. In Fig. 3d, a semi-log plot displays the dependence of the current density on the applied bias voltage, exhibiting an exponential profile typical of tunnel junctions. When the applied voltage exceeds 1.25 V, the detected light intensity by a single photon counter increases linearly with the electric current in the shaded violet area. The transition between the direct-tunneling and field-emission regimes is illustrated in the Fowler-Nordheim representation of the l(V) data in Fig. 3e, which shows a minimum at a voltage of 0.8 V. The l-V data is fit with the Simmons model, assuming an effective electron mass of 0.23me. From this analysis, the extracted values were determined of the junction’s mean barrier height (p = 2.62 eV and barrier width As = 3.2 nm. The inconsistency of fitting results with TEM data indicates the presence of local (antenna-scale) inhomogeneities of the barrier layer and surface charge phenomena that could contribute to diminishing of the effective tunneling barrier width.

[0261] The optical properties of LIET was studied in detail by measuring the dependence of the emission spectra on applied bias voltage. Figure 4a shows the corresponding spectra recorded from the optimized metasurface within the 500 to 950 nm spectral range for a bias voltage Vbincreasing from 1.5 to 2.3 V. One observes two major trends in the spectra: first, the emission band shifts to shorter wavelengths with increasing Vb, which is explained by the linear change in the cutoff condition with the energy of the emitted photons: hwmax= |eVb|; second, for high enough Vb(>1.9 V), the spectra start to manifest a pronounced peak close to 650 nm. The change of Vbwithin the 1.5-2.3 V range leads to an increase of the total signal intensity as well as a gradual blueshift of the shorter wavelength peak.

[0262] To elaborate on the origin of the observed spectral features and their evolution with bias voltage, the Inventors introduce a theoretical model that describes both the tunneling process and the antenna-assisted coupling of LIET to the far-field. The spectrally resolved LIET intensity is calculated as

[0263] l[_IET(w. Vb) oc H(w, Vb) ■ G(w),

[0264] where the electron tunneling efficiency H(oj,Vb) across the tunneling layer is introduced as a function of photon frequency co and applied potential Vb, and the antenna-mediated photon emission efficiency G(co). Results from the simulations closely reproduce the spectral features of the emission observed in the experiment (Fig. 4c) as well as their evolution with increasing Vb (Figs. 4a, 4b).

[0265] Importantly, the model allows to discriminate the contributions of the tunneling efficiency H(co,Vb) and the antenna-mediated emission efficiency G(co) to the resulting spectra. Figures 4d and 4e show the spectral dependence of these two functions plotted separately for Vb = 2.3 V. The tunneling efficiency H(co, Vb) has no pronounced spectral features (Fig. 4d) and its contribution to the total emission intensity is mainly consisting of a gradual increase towards longer wavelengths. In contrast, G(co) (Fig. 4e) shows strong spectral variations associated with the plasmonic modes of the nanowire antenna 15. The main observed feature is a sharp peak at 550 nm, which corresponds to a mode of dipolar nature. This is confirmed by simulations of the electric near field of the nanowire for linearly polarized plane-wave excitation: the field calculated fora lightwavelength of 650 nm (Fig. 4c, inset in left box) shows two characteristic hotspots at the top surface of the antenna 15. It is also observed a minor increase of G(OJ) at longer wavelengths (850 nm). This corresponds to the wing of another peak outside of the experimentally studied spectral region. Numerical simulations of the nearfield distribution for plane-wave excitation at 900 nm (Fig. 4c, inset in right box) reveal a strong enhancement in the AI2O3 insulating layer, which is beneficial in assisting the inelastic tunneling process. These observations, along with simulations in a broader spectral range, allow us to identify the dominant spectral feature as a plasmonic gap mode or a gap plasmon or gap surface plasmon.

[0266] Biosensing with self-illuminating metasurface 21 of the device 1 was performed. To benchmark the exemplary on-chip LIET-based optical biosensor 1 , the device was tested with two distinct organic analytes: a 45 nm thick polymethyl methacrylate (PMMA) polymer layer and a film of protein A / G.

[0267] The LIET image of the metasurface covered with PMMA and biased with a sufficiently high voltage to induce tunneling luminescence is shown in Fig. 5a. To illustrate the changes in the emission intensity and the spectrum with and without analyte, after spin-coating a uniform layer of PMMA on the sensor surface, electron-beam exposure is used and subsequent development steps to selectively remove the polymer and create PMMA-free regions. Figure 5a shows a rectangularly shaped bare region (top box) that is used for reference spectra measurements as well as a patterned region in the form of the EPFL logo. The image shows a significantly higher emission intensity on the areas covered with the analyte film compared to the bare regions, and the intensity distribution is spatially uniform.

[0268] Further insight is provided by the emission spectra shown in Fig. 5b, which are measured from the bare and an analyte-covered regions of interest on the functionalized LIET device 1 . The spectra reveal that the stronger emission intensity in the LIET image is mainly due to enhancement of the shorter wavelength peak corresponding to the dipolar plasmonic mode of the nanowire antenna 15. Forthe bias voltage applied (Vb=2.8 V), the initial emission spectrum has a peak at around 620 nm. The PMMA presence leads to the red-shifting of this peak up to 70 nm as well as a 2.3-fold increase in its intensity.

[0269] To test protein A / G as the analyte 33, it is introduced on the sample surface by drop casting protein A / G stock and subsequently drying it to form the film. Compared to the PMMA layer, where the reference regions are spatially well defined by the lithography steps, the protein layer has a varying thickness due to the employed drop-casting method. As Fig. 5d, shows, this leads to a radially decreasing emission intensity distribution, with the area with more analyte having higher intensity. Similarly to PMMA, one immediately notices the pronounced effect of the analyte on the intensity of the LIET, which increases with the thickness of the layer.

[0270] Further insight is provided by the emission spectra measured from bare and analyte-covered regions of interest on the functionalized LIET devices that are shown in Figs. 5b, 5e. The analyte-covered region of interest shows that protein A / G induces up to a 50 nm red shift of the peak associated with the dipolar plasmonic mode (centered at around 630 nm forthe bare area) and a 1 .45-fold increase in its intensity. Incidentally, differences in the shape of the emission spectra as compared to PMMA sample are due to variations of the tunnel junction parameters across different chips.

[0271] To elaborate on the origin of spectral redshift and intensity increase of the emission due to the presence of analytes, the Inventors use the theoretical model discussed above. In the simulations, analytes are represented as layers of uniform thickness and constant refractive index (1.49 for PMMA and 1.35 for Protein A / G). Their thicknesses are set at 45 nm for PMMA and 15 nm forthe protein. The spectral shifts observed for PMMA show good agreement with the results of the simulations (Fig. 5c). The measured spectral shift and intensity increase of the emission peak for protein functionalization (Fig. 5f) exceeds the prediction of the theoretical model, which suggests additional mechanisms that are not accounted in the theory, such as the effect of variations in analyte thickness.

[0272] For both cases, one observes that the gap mode or plasmonic gap mode that resides in the long-wavelength region of the spectra is not strongly affected by the functionalization, a result that this is interpreted in terms of a weak spatial overlap between the associated near-field and the analyte in that spectral region. The increase of the short wavelength peak amplitude is reproduced in the simulations and can be explained by the improved impedance matching for antenna mode that enhances the fa r-field light out-coupling efficiency.

[0273] The spectral and / or intensity characteristics of the generated light emission of the device 1 permits sensing or detection. Measurement of the generated light emission to determine a wavelength shift (for example, red-shift or blue-shift) in the luminesce emission spectrum and / or a change in intensity, (for example, an augmentation or reduction) of the luminesce emission spectrum permits sensing or detection of an entity, analyte and / or substance received on the device 1.

[0274] As explained above and shown in Figure 1C and Figures 5b, 5c, 5e and 5f, the sensing surfaces 17 receive, directly or indirectly, an entity, analyte or substance to wavelength shift at least one spectral portion of the luminesce emission spectrum of the plasmonic biosensor device 1 . The spectral portion may, for example, red-shift or blue-shift, with a red-shift shown in the exemplary embodiment of Figure 1 C and Figures 5b, 5c, 5e and 5f. The spectral portion may, for example, increase or decrease in light emission intensity with an increase shown in the exemplary embodiment of Figure 1 C and Figures 5b, 5c, 5e and 5f. The spectral portion may, for example, be a plasmonic spectral feature SC of the luminesce emission spectrum of the plasmonic biosensor device. Sensing or detection can be implemented by determining a wavelength shift (for example, red-shift or blue-shift) in the luminesce emission spectrum of the plasmonic spectral feature SC and / or a change in intensity, (for example, an augmentation or reduction) of the luminesce emission spectrum of the plasmonic spectral feature SC at one or more wavelength values of the plasmonic spectral feature SC.

[0275] As seen in Figure 1C and 5, the wavelength shift may be, for example, a wavelength shift (or displacement) of at least one wavelength valuerefi (or at least one reference wavelength value refi) of a spectral peak or spectral characteristic SC of the bare device 1 in the luminesce emission spectrum. As mentioned, the spectral peak or spectral characteristic SC is, for example, a plasmonic spectral feature SC of the luminesce emission spectrum of the plasmonic biosensor device 1. That is, a spectral feature in the light emission produced or resulting from the plasmon or plasmonic modes of the plasmonic structure 11 and / or the (interconnected) optical nanoantennas 15, as described herein.

[0276] Light at this wavelengthrefi (reference wavelengthrefi) in the spectral range of the plasmonic spectral feature SC is, for example, wavelength shifted (blue or red shifted) by the entity, analyte and / or substance, and / orthe light intensity at this wavelength (reference wavelength) in the spectral range of the plasmonic spectral feature SC is, for example, changed (increased or decreased).

[0277] In the exemplary embodiment of Figure 1 C and Figures 5b, 5c, 5e and 5f, the wavelengthrefi is red-shifted by the presence of the sample material, and there is a reduction in intensity in the example of Figure 1 C, while there is an increase in intensity in the exemplary embodiment of Figure 5b. The spectral shift and intensity change are sample dependent.

[0278] For example, the wavelength valuerefi or reference wavelength valuerefi may be a wavelength PK1 at which the spectral peak or spectral characteristic SC has a maximum intensity value (or at least one of the maximum intensity values of the spectral peak or spectral characteristic SC in the case where several different wavelengths have the same maximum intensity values). Alternatively, for example, the wavelength valuerefi (or reference wavelengthrefi) and the emission intensity at that wavelength value (of the bare device) can be compared to a comparison wavelength value / .ref2 (or comparison reference wavelength / .ref2) of the plasmonic spectral feature SC of the device including the entity, analyte and / or substance. The comparison wavelength value / .ref2 can also be defined to be at a value PK2 of the spectral peak or spectral characteristic SC that has a maximum intensity value (or at least one of the maximum intensity values of the spectral peak or spectral characteristic SC in the case where several different wavelengths have the same maximum intensity values).

[0279] Alternatively, for example, the wavelengthrefi (or reference wavelengthrefi) can be defined at the FWHM center wavelength of the plasmonic spectral feature SC of the bare device and compared to the FWHM center wavelength / .ref2 that defines a comparison wavelength value ret2 (orthe comparison reference wavelength / .ref2) ofthe plasmonic spectral feature SC of the device including the entity, analyte and / or substance. The determination of wavelengthsrefi, ret2 using the full width half-maximum FWHM that is the central wavelength between and / or of the wavelengths at the 50% intensity value of the maximum intensity value is exemplary, and a value of 75% or 85% or 95% ofthe maximum intensity value may be used.

[0280] Alternatively, for example, a range of wavelengths Rrefi (or reference range Rrefi) can be defined between the FWHM wavelengths of the plasmonic spectral feature SC of the bare device and compared to a wavelength range Rref2 that defines a comparison range Rref2 (orthe comparison reference range Rref2) ofthe plasmonic spectral feature SC ofthe device including the entity, analyte and / or substance. A wavelength shift is for example determined by a shift ofthe wavelength range and an intensity change determined by comparing in an accumulated intensity ofthe wavelength ranges Rrefi , Rret2. Similarly, The determination of ranges Rrefi , Rret2 using the full width half-maximum FWHM that is the central wavelength between and / or of the wavelengths at the 50% intensity value of the maximum intensity value is exemplary, and a value of 75% or 85% or 95% ofthe maximum intensity value may be used.

[0281] It is however noted that other wavelength values or other reference wavelength values can be used during such a comparison of the bare device emission to the received sample / entity device emission.

[0282] In summary, an exemplary self-illuminating plasmonic sensor 1 is provided in which light emission is provided by quantum tunnel junctions 7. The design features a bottom (aluminum) electrode 3, with a thin isolating layerof alumina formed by thermal oxidation ofthe film, acting as a tunneling barrier 7. The upper electrode 5 includes, for example, a doubly periodic metasurface 21 made of resonant gold nanowire antennas 15 that simultaneously provide enhanced electron-to-light conversion and far-field light emission due to the mediation of plasmonic antenna modes. The metasurface 21 undergoes optimization to provide exquisite spatially uniform and large-area emission that is highly advantageous for the good performance of the proposed sensors 1 .

[0283] The electro-optical properties of the devices 1 and their spectral performance toward the detection of different types of analytes are well explained by theoretical modeling incorporating microscopic details of the tunneling process as well as the electromagnetic response associated with plasmonic antenna modes. It is demonstrated that the emission peak at shorter wavelengths that originates from the resonant mode of the nanowire antennas allows spatially resolved refractometric sensing with ourdevice. This sensing concept is validated for a thin film of polymer and a biomolecule layer.

[0284] Additional insight could be gained by resorting to angle-resolved photodetection, as the angulardistribution of the emission is intimately related to the frequency of the excited modes. The evolution of the observed angle-resolved emission patterns indicates the possibility of photodetection along selected angular windows as a way to gain spectral selectivity without the need to use an optical spectrometer.

[0285] In addition, because the employed metal films are polycrystalline, the effect of conservation of in-plane electron momentum is substantially erased by averaging over grain orientations. The tunneling process should instead be dominated by specific in-plane momentum components via the use of crystalline surfaces with a well-defined crystal orientation. This provides an additional knob to gain control over the inelastic tunneling process.

[0286] The inherently low efficiency of emission from inelastic electron tunneling is compensated in the approach of the present disclosure design not only by antenna-driven enhancement but also by having a lithographically defined large area of emission. Such planar device geometry enables the potential of large-scale fabrication and the potential fora general-purpose electro-optical biosensing platform and other novel applications.

[0287] For fabrication of an exemplary sensor device 1 , the LIET device 1 was fabricated on a commercially available glass coverslip measuring 22x22x0.13mm3. The bottom metal electrode was designed using UV laser photolithography (VPG 200, Heidelberg Instruments, Germany), while the metasurface 25 and top electrode 5 were defined by the e-beam lithography (Raith EBPG5000+). Each metal thin film was deposited through e-beam evaporation using a Leybold Optics LAB 600H evaporator.

[0288] The bottom electrode 3 was formed by depositing aluminum (Al) through the designed photoresist layer and subsequently lifting it off. Then, the AI2O3layer 7 was formed using a thermal oxidation process in a Neytech furnace (Qex) at 200°C for 3 hours. After forming the AI2O3 tunnel barrier 7, a Cr adhesion layer was deposited as well as the top Au electrode 5 using a patterned e-beam resist. Subsequently, the e-beam resist layers were removed through a lift-off process, resulting in the formation of a metasurface 21 connected with a top electrode. Electrical connections from the bottom and top Al and Au electrodes were established by connecting them to a PCB board with Au wire using a wire bonder (F&S Bondtec 5630i Semiconductor GmbH).

[0289] As mentioned, the LIET device 1 was fabricated on a commercially available glass coverslip 19 measuring 22x22x0.13mm3, as schematically illustrated in the process flow in Figs. 2a-g.

[0290] Before delineating the electrode with nanostructures, a bulk alignment marker was defined using UV laser photolithography (VPG 200, Heidelberg Instruments, Germany) with a Bi-layer resist of LOR 5A I AZ1512HS (Kayaku advanced materials, MicroChemicals), as shown in Fig. 2a. Following this process, an adhesion layer of 5 nm Cr layer and a thin film of 100 nm Au were deposited, and the photoresist was developed using MIF 712. After creating an alignment marker, the bottom electrode 3 was defined using the same lithography tool and photoresist, as shown in Fig. 2b.

[0291] Subsequently, a 25 nm layer of Al was deposited via an e-beam evaporator (base pressure of 1 .8 x io-6mbar) at a deposition rate of 4.0 A / s (Leybold Optics LAB 600H), followed by liftoff of the resist. Next, the AI2O3layer (acting as the electron tunneling barrier 7 in the devices 1) was formed through thermal oxidation in a Neytech furnace (Qex) at 200°C for 3 hours, with a ramping rate of 50°C / min (see Fig. 2c).

[0292] The sample was extracted from the furnace upon reaching room temperature. The stability of the tunnel junction 7 was notably sensitive to this final temperature, and therefore, this protocol was followed to ensure the stability of the tunnel junction 7. After defining the AI2O3tunnel barrier 7, e-beam lithography (Raith EBPG5000+) was employed to delineate a nanomesh structure 21 with a top electrode. The e-beam resist for this pattern consisted of a double layer using MMA EL6 and PMMA 950 K A2. To prevent the e-beam charging effect on these two resists, a thin Au layer was sputtered on top of the e-beam resist, as shown in Fig. 2d. Following e-beam writing and development of these two layers, as shown in Fig. 2e, the adhesion layer 9 of 5nm Cr and the 50 nm Au layer 5 were deposited using an e-beam evaporator, and the resist was lifted off using a suitable solution (MiBK:IPA=1 :3 solution), as shown in Fig. 2f.

[0293] The final device was formed as shown in Figs. 2g and 2i (cross-sectional and top views, respectively).

[0294] The geometrical parameters of the device 1 were analyzed using a bright- field high-resolution transmission electron microscope (HRTEM, Fig. 2h), and then, the composition of each layer was measured by energy dispersive spectroscopy (EDS) in scanning transmission electron microscopy (STEM) mode.

[0295] For functionalization of LIET devices 1 with polymer and protein layers, and for the exemplary on-chip LIET-based optical biosensori , two types of analytes were prepared: PMMA and nonlabeled protein A / G. For the former, PMMA 495k A2 (Sigma-Aldrich) was used, which was coated onto the substrate using a spin-coating machine at 6000 rpm for 60 seconds. Subsequently, the sample was baked at 180°C for 5 minutes. To open an area for reference measurements, PMMA layer was patterned using an e-beam. After the exposure, the resist was developed using a MiBK:IPA=1 :3 solution for 1 minute. The resulting analyte layer had a thickness of approximately 45 nm, and a refractive index of 1 .49.

[0296] For the functionalization with protein A / G (a recombinant fusion protein with protein A- and G-binding sites, a molecular weight of 50 kDa, and a refractive index of 1.35-1.6040), additional materials were prepared, including Acetate buffer (pH 4), Glycerol, and Phosphate-buffered saline (PBS, pH 7.4). A 0.5 mg / ml protein A / G solution was prepared in 10 mM Acetate buffer with 0.5% Glycerol and applied to the metasurface 21 . Prior to this, the metasurface 21 had been treated with O2plasma to create a negative charge on the surface. After a 2-hour incubation period, the chip was washed in PBS buffer for 5 minutes under constant agitation to remove excess protein, followed by rinsing with water.

[0297] Analyte characterization was performed by conducting an investigation into the functionalization of two analytes, PMMA and protein AG, on the LIET device 1 using an optical microscope, an EMCCD-based real-plane image, and an atomic force microscope (AFM). As detailed previously and in Fig. 6A, one of the target analytes (PMMA 495k A2) was patterned using e-beam lithography and lifted off using a developer solution (MiBK:IPA=1 :3). Area 1 featured a mesh metasurface 21 without analyte, while Area 2 had a mesh metasurface 21 coated with analyte PMMA. Both of these areas were characterized by EMCCD to compare the intensity of the generated light through the LIET device, as illustrated in Fig. 6B. The mesh metasurface 21 alone had a height of about 55 nm, whereas the analyte had a thickness of about 45 nm, as measured by AFM and depicted in Fig. 6C.

[0298] Similarly, the analyte protein AG was applied to the LIET device 1 using the drop-casting method, as depicted in Fig. 6D-6E, followed by cleaning the remaining analytes not bound to the surface. As illustrated in the EMCCD map in Fig. 6F, there was an intensity gradient attributed to the varying thickness resulting from the drop-casting method. Through AFM measurements as shown in Fig. 6G, it was determined that the thickness of the protein AG coated on the mesh metasurface was in the range of 10-15 nm, whereas the aggregated form of protein AG appeared to be approximately 30 nm.

[0299] For sample characterization, all optical measurements were conducted using a customized inverted Nikon microscope (Ti-E). For optical response measurements without biasing, the reflection mode of the microscope with a halogen lamp was employed, which was focused onto the top objective (50x with NA 0.8, or 100x with NA 0.9). The emitted light from the LIET devices 1 under electrical biasing was collected using a dry objective with a high numerical aperture (100x, NA 0.9). The spectrally resolved measurements were performed with an IsoPlane 320 Spectrometer using a Pixis camera from Princeton Instruments. All spectra were normalized to account for system efficiency, acquisition time, and sampling rate, resulting in emission spectra quantified in counts / s / nm unit.

[0300] Real-plane and back-focal-plane images of the metasurface emission were captured using an Andor iXon Ultra EMCCD camera (model 888). For the experiments, the optical path in the signal collection channel was customized by introducing and additional linear polarizer and a Bertrand lens before the tube lens that formed the image on the EMCCD camera. Switching between real-plane and back-focal-plane imaging regimes was achieved by adding or removing the Bertrand lens from the optical path.

[0301] Electrical biasing was performed using a Keithley 2636B source-meter along with Kickstart software from Linktronix. Material characterization was conducted through various techniques, including scanning electron microscopy (SEM, MERLIN Zeiss Gemini II), transmission electron microscopy (TEM, Tecnai Osiris), and atomic force microscopy (AFM, Bruker FastScan). Electroluminescence characterization was performed and the optical properties of each LIET device 1 was characterized using a customized inverted optical microscope (Ti-E) equipped with a) an electron multiplying CCD (EMCCD, iXon Ultra 888) and b) a spectrometer (Isoplane 320 Spectrometer with a Pixis camera from Princeton Instrument).

[0302] The optical characteristics were measured with 50x (NA=0.8) and 100x (NA=0.9) objectives when the junction 7 was biased (i.e., Au biased and Al grounded). A 300 EM gain was emplyed to record EMCCD images for both the real and the back- focal planes.

[0303] In Fig. 7A, the optical paths for the real plane (image plane) and back-focal plane images are indicated by the light-solid and dark-solid lines, respectively. During the recording of backfocal plane images, an additional lens (Bertrand lens) was used in conjunction with the tube lens. To investigate polarization effects, an additional polarizerwas introduced when recording both real and back-focal plane images.

[0304] For spectral measurements, the generated light was collected through the objective and then directed to the spectrometer, as shown in Fig. 7B. A correct interpretation of electroluminescence spectra necessitates taking into consideration the spectral transfer function of the detection path. The wavelength-dependent transfer function of all individual elements, as well as the quantum efficiency (QE) of the EMCCD, were obtained from the manufacturers. Using this data, corrected spectra and emitted photon numbers were calculated. To obtain spectra that are independent of exposure time and pixel size, corresponding to AA, and to form the final version of the spectrum, corrected spectra were derived according to

[0305] j _

[0306]

[0307] c / ;A( AA

[0308] where lc, , lb, and ltare the corrected, initial, background, and transfer-function intensities, respectively, while At represents the given exposure time, and each data point reflects the photon counts on individual pixels. The quantity AA denotes the difference in nanometers between two consecutive measurement points. The units of the corrected intensity lcare counts per second per nanometer.

[0309] This normalization ensures that the spectrum is independent of exposure time and pixel size, providing a reliable measure of the emitted light intensity across different wavelengths. For additional optical characterization, an avalanche photodiode (APD, Excelitas Technologies SPCM-AQRH-14 APD) was employed to monitor the photons emitted from the LIET devices 1 under room temperature and ambient conditions. All electrical excitation and characterization procedures were conducted using a Keithley 2636 B source-meter in conjunction with the Kickstart software from Linktronix. Both l-V (current-voltage) and l-t (current-time) modes were utilized, with current recording occurring typically every 100 ms. This comprehensive approach allowed for a thorough assessment of the electrical characteristics of the LIET devices 1.

[0310] In relation to the stability of electrical and optical properties, the width and quality of the AI2O3 LIET device tunnel layer are expected to influence both the intensity and stability of the tunnel current. The field strength of the LIET device 1 was measured to be 4 x 109V / m at room temperature under ambient conditions for a duration of 13 minutes during which a voltage of 2.0 V was maintained. During the initial 10 minutes of recording, a minor increase in tunneling current was observed, with no significant fluctuations throughout the entire measurement period. Following the electrical stability test, the electroluminescence stability was assessed based on the applied voltage, comparing samples before and after the 13-minute electrical stability test. Despite the fact that experiments were conducted under ambient conditions, the tunnel junction demonstrated good stability in both electrical and optical characteristics, even with a relatively large LIET-based sensing area of approximately 300 pm x 300 pm.

[0311] In Fig. 8, the resulting tunneling efficiency H(OJ, Vb) is compared with and without inclusion of in-plane momentum conservation for a bias voltage Vbin the 1.5-2.3 V range. Under positive bias, electrons tunnel from the polycrystalline Al layer to the polycrystalline Cr layer. As excpected, the two results are identical, so one concludes that parallel-momentum conservation can be disregarded for tunneling between polycrystalline metal surfaces, and only energy conservation needs to be incorporated.

[0312] Electromagnetic mode analysis was performed through the angle- resolved emission efficiency, and further insight into the nature of the excitation of plasmonic modes of the metasurface devices 1 can be revealed by examining their electric field distributions. In Fig. 9, the angle-resolved radiation efficiency is studied at selected wavelengths from 500 nm to 725 nm, from which it is determined the incident angles 0 and (p that can excite the plasmonic modes at specific wavelengths. The excitation of a plasmonic mode by light incident from a given direction is connected by reciprocity to the emission of light along that direction via radiative de-excitation of the same mode, which is considered to be previously excited by inelastic electron tunneling in the present context. The angles 0 and (p play an important role in determining the modes collected for each wavelength, indicating that additional insight into the LIET process could be gained by resorting to angle-resolved photodetection. However, for the present, in which the photoluminescence signal is collected through an objective lens, one integrates over emission angles and, therefore, calculate the antenna-mediated photonemission efficiency as

[0313]

[0314] oc ' J d# sin 8 f <?)

[0315] where the 0 integral is limited by the numerical aperture of the optical system. Figure 9 shows the angle-resolved radiation efficiency G(oj,0,(p) at selected wavelengths from 500 nm to 725 nm. Results are shown up to a maximum polar angle 0 = 54°, as determined by the numerical aperture NA= 0.8 of the objective used in experiment to collect the emission signal.

[0316] Implementations described herein are not intended to limit the scope of the present disclosure but are just provided to illustrate possible realizations.

[0317] The word “about” as used herein means the identified value plus / minus 5%.

[0318] Sub-wavelength means sub-wavelength at a device operation wavelength of the device 1 or intended device operation wavelength of the device 1, unless otherwise specified.

[0319] Each embodiment herein may be used in combination with any other embodiments) described herein.

[0320] “On” as used herein covers both directly on, and indirectly on with intervening element(s) therebetween. Thus, for example, if element A is stated to be “on” element B, this covers element A being directly and / or indirectly on element B. Likewise, “supported by” as used herein covers both in physical contact with, and indirectly supported by with intervening element(s) therebetween.

[0321] While the disclosure has been illustrated and described with reference to various example embodiments, it will be understood that the various embodiments are intended to be illustrative, not limiting. It will further be understood by those skilled in the art that various changes in form and detail may be made without departing from the true spirit and full scope of the disclosure, including the appended claims and their equivalents. It will also be understood that any of the embodiments) described herein may be used in combination with any other embodiments) described herein. Extremity values in ranges are included in the specified range. REFERENCES

[0322] 1. Maier, S. A. Plasmonics: Fundamentals and Applications; Springer US.

[0323] 2. Homola, J. Surface plasmon resonance sensors for detection of chemical and biological species. Chemical reviews 2008, 108, 462-493.

[0324] 3. Mayer, K. M.; Hafner, J. H. Localized Surface Plasmon Resonance Sensors. Chem. Rev.

[0325] 2011 , 111 , 3828-3857.

[0326] 4. Chen, P.; Chung, M. T.; McHugh, W.; Nidetz, R.; Li, Y.; Fu, J.; Cornell, T. T.; Shan- ley, T. P.; Kurabayashi, K. Multiplex Serum Cytokine Immunoassay Using Nanoplas- monic Biosensor Microarrays. ACS Nano 2015, 9, 4173-4181 .

[0327] 5. Belushkin, A.; Yesilkoy, F.; Gonza lez-Lo pez, J. J.; Ruiz-Rodnguez, J. C.; Ferrer, R.; Fa'brega, A.; Altug, H. Rapid and Digital Detection of Inflammatory Biomarkers Enabled by a Novel Portable Nanoplasmonic Imager. Small 2020, 16, 1906108.

[0328] 6. Ansaryan, S.; Liu, Y.-C.; Li, X.; Economou, A. M.; Eberhardt, C. S.; Jandus, C.; Al- tug, H. High-throughput spatiotemporal monitoring of single-cell secretions via plas- monic microwell arrays. Nat. Biomed. Eng. 2023, 7, 943-958.

[0329] 7. Lee, C.; Lawrie, B.; Pooser, R.; Lee, K.-G.; Rockstuhl, C.; Tame, M. Quantum Plasmonic Sensors. Chem. Rev. 2021 , 121 , 4743-4804.

[0330] 8. Lee, J.; Jeon, D.-J.; Yeo, J.-S. Quantum plasmonics: energy transport through plasmonic gap. Advanced Materials 2021 , 33, 2006606.

[0331] 9. Baumberg, J. J. Picocavities: a Primer. Nano Lett. 2022, 22, 5859-5865.

[0332] 10. Baumberg, J. J.; Aizpurua, J.; Mikkelsen, M. H.; Smith, D. R. Extreme nanophotonics from ultrathin metallic gaps. Nature Materials 2019, 18, 668-678.

[0333] 11. Ye, F.; Merlo, J. M.; Burns, M. J.; Naughton, M. J. Optical and electrical mappings of surface plasmon cavity modes. Nanophotonics 2014, 3, 33-49.

[0334] 12. Lambe, J.; McCarthy, S. L. Light Emission from Inelastic Electron Tunneling. Phys. Rev. Lett. 1976, 37, 923-925

[0335] 13. Dong, Z. C.; Zhang, X. L.; Gao, H. Y.; Luo, Y.; Zhang, C.; Chen, L. G.; Zhang, R.; Tao, X.; Zhang, Y.; Yang, J. L.; Hou, J. G. Generation of molecular hot electrolumines- cence by resonant nanocavity plasmons. Nat. Photonics 2010, 4, 50-54.

[0336] 14. Schuler, B.; Cochrane, K. A.; Kastl, C.; Barnard, E. S.; Wong, E.; Borys, N. J.; Schwartzberg, A. M.; Ogletree, D. F.; de Abajo, F. J. G.; Weber-Bargioni, A. Electri- cally driven photon emission from individual atomic defects in monolayer WS2. Science advances 2020, 6, eabb5988.

[0337] 15. Yu, A.; Li, S.; Wang, H.; Chen, S.; Wu, R.; Ho, W. Visualization of nanoplasmonic coupling to molecular orbital in light emission induced by tunneling electrons. Nano Letters 2018, 18, 3076-3080. 16. Zhang, Y.; Luo, Y.; Zhang, Y.; Yu, Y.-J.; Kuang, Y.-M.; Zhang, L.; Meng, Q.-S.; Luo, Y.; Yang, J.-L.; Dong, Z.-C.; Hou, J. G. Visualizing coherent intermolecular dipole-dipole coupling in real space. Nature 2016, 531 , 623-627.

[0338] 17. Merino, P.; Roslawska, A.; Leon, C. C.; Grewal, A.; GroBe, C.; Gonz alez, C.; Kuhnke, K.; Kern, K. A single hydrogen molecule as an intensity chopper in an electrically driven plasmonic nanocavity. Nano letters 2018, 19, 235-241.

[0339] 18. Qin, H.; Sorkin, V.; Pei, Q.-X.; Liu, Y.; Zhang, Y.-W. Failure in two-dimensional ma- terials: Defect sensitivity and failure criteria. Journal of Applied Mechanics 2020, 87, 030802.

[0340] 19. Yersak, A. S.; Lee, Y.-C. Probabilistic distributions of pinhole defects in atomic layer deposited films on polymeric substrates. Journal of Vacuum Science & Technology A 2016, 34.

[0341] 20. Parzefall, M.; Bharadwaj, P.; Jain, A.; Taniguchi, T.; Watanabe, K.; Novotny, L. Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions. Nat. Nanotechnol.

[0342] 2015, 10, 1058-1063.

[0343] 21. Parzefall, M.; Szabo , A .; Taniguchi, T.; Watanabe, K.; Luisier, M.; Novotny, L. Light from van der Waals quantum tunneling devices. Nature communications 2019, 10, 292.

[0344] 22. Namgung, S.; Mohr, D. A.; Yoo, D.; Bharadwaj, P.; Koester, S. J.; Oh, S.-H. Ultrasmall plasmonic single nanoparticle light source driven by a graphene tunnel junction. ACS nano 2018, 12, 2780-2788.

[0345] 23. Wang, L.; Papadopoulos, S.; lyikanat, F.; Zhang, J.; Huang, J.; Taniguchi, T.; Watan- abe, K.; Calame, M.; Perrin, M. L.; Garc ia de Abajo, F. J.; Novotny, L. Exciton-assisted electron tunnelling in van der Waals heterostructures. Nat. Mater. 2023, 22, 1094-1099.

[0346] 24. Papadopoulos, S.; Wang, L.; Taniguchi, T.; Watanabe, K.; Novotny, L. Energy transfer from tunneling electrons to excitons. arXiv preprint arXiv:2209.11641 2022,

[0347] 25. Qian, H.; Li, S.; Hsu, S.-W.; Chen, C.-F.; Tian, F.; Tao, A. R.; Liu, Z. Highly-efficient electrically-driven localized surface plasmon source enabled by resonant inelastic electron tunneling. Nature communications 2021 , 12, 3111.

[0348] 26. Kern, J.; Kullock, R.; Prangsma, J.; Emmerling, M.; Kamp, M.; Hecht, B. Electrically driven optical antennas. Nature Photonics 2015, 9, 582-586.

[0349] 27. Bigourdan, F.; Hugonin, J.-P.; Marquier, F.; Sauvan, C.; Greffet, J.-J. Nanoantenna for Electrical Generation of Surface Plasmon Polaritons. Phys. Rev. Lett. 2016, 116, 106803. 28. Gurunarayanan, S. P.; Verellen, N.; Zharinov, V. S.; James Shirley, F.; Moshchalkov, V. V.; Heyns, M.; Van de Vondel, J.; Radu, I. P.; Van Dorpe, P. Electri- cally driven unidirectional optical nanoantennas. Nano letters 2017, 17, 7433-7439.

[0350] 29. Kullock, R.; Ochs, M.; Grimm, P.; Emmerling, M.; Hecht, B. Electrically-driven Yagi- Uda antennas for light. Nature communications 2020, 11 , 115. 30. Qian, H.; Hsu, S.-W.; Gurunatha, K.; Riley, C. T.; Zhao, J.; Lu, D.; Tao, A. R.; Liu, Z. Efficient light generation from enhanced inelastic electron tunnelling. Nature Photonics 2018, 12, 485-488.

[0351] 31. Liu, L.; Krasavin, A. V.; Li, J.; Li, L.; Yang, L.; Guo, X.; Dai, D.; Zayats, A. V.; Tong, L.; Wang, P. Waveguide-Integrated Light-Emitting Metal-lnsulator-Graphene Tunnel June- tions. Nano Lett. 2023, 23, 3731-3738.

[0352] 32. Dathe, A.; Ziegler, M.; Hu bner, U.; Fritzsche, W.; Stranik, O. Electrically Excited Plas-monic Nanoruler for Biomolecule Detection. Nano Lett. 2016, 16, 5728-5736.

[0353] 33.Wang, P.; Krasavin, A. V.; Nasir, M. E.; Dickson, W.; Zayats, A. V. Reactive tun- nel junctions in electrically driven plasmonic nanorod metamaterials. Nat. Nanotechnol. 2018, 13, 159-164.

[0354] 34. Du, W.; Wang, T.; Chu, H.-S.; Nijhuis, C. A. Highly efficient on-chip direct electronic-plasmon ic transducers. Nature Photonics 2017, 11, 623-627.

[0355] 35. Zhang, C.; Hugonin, J.-P.; Coutrot, A.-L.; Sauvan, C.; Marquier, F.; Greffet, J.-J. An-tenna surface plasmon emission by inelastic tunneling. Nat. Commun. 2019, 10, 1-7.

[0356] 36. Simmons, J. G. Electric Tunnel Effect between Dissimilar Electrodes Separated by a Thin Insulating Film. J. Appl. Phys. 1963, 34, 2581-2590.

[0357] 37. Groner, M.; Elam, J.; Fabreguette, F.; George, S. M. Electrical characterization of thin AI2O3 films grown by atomic layer deposition on silicon and various metal substrates. Thin solid films 2002, 413, 186-197.

[0358] 38. Oborina, E. I.; Benjamin, H. N.; Hoff, A. M. Fowler-Nordheim analysis of oxides on 4H-SiC substrates using noncontact metrology. J. Appl. Phys. 2009, 106 .

[0359] 39. Beadie, G.; Brindza, M.; Flynn, R. A.; Rosenberg, A.; Shirk, J. S. Refractive index measurements of poly (methyl methacrylate)(PMMA) from 0.4-1.6 pm. Applied optics 2015, 54, F139-F143.

[0360] 40. Voros, J. The density and refractive index of adsorbing protein layers. Biophysical journal 2004, 87, 553-561.

[0361] The disclosure of each of the above references is hereby incorporated herein by reference in its entirety for all purposes

Claims

CLAIMS1. Plasmonic biosensor device (1) comprising:- a first electrode (3),- a second electrode (5); and- at least one charge carrier tunnelling junction (7) for providing charge carriers for generating light emission by electroluminescence, the at least one charge carrier tunnelling junction (7) being in electrical connection with the first electrode (3) and the second electrode (5) for application of a voltage potential difference to the at least one charge carrier tunnelling junction (7),wherein the second electrode (5) comprises or forms a plasmonic structure (11) including a plurality of electrically interconnected optical nanoantennas (15) configured to generate plasmons and light emission via the charge carriers provided by charge carrier tunneling in the at least one charge carrier tunnelling junction (7), the plurality of optical nanoantennas (15) being located and extending on the at least one charge carrier tunnelling junction (7); andwherein the nanoantennas (15) each include a sensing surface (17), and the sensing surfaces (17) are disposed on the plasmonic biosensor device (1) to receive, directly or indirectly on the sensing surface (17), at least one of an entity, analyte and substance to wavelength shift at least one spectral portion of the luminesce emission spectrum of the plasmonic biosensor device (1).

2. Plasmonic biosensor device (1) according to claim 1 , wherein the sensing surfaces (17) are disposed on the plasmonic biosensor device (1) to receive, directly or indirectly on the sensing surface (17), at least one of the entity, analyte and substance to wavelength shift a plasmonic spectral feature (SC) of the luminesce emission spectrum of the plasmonic biosensor device (1).

3. Plasmonic biosensor device (1) according to claim 2, wherein light at, at least one wavelength (refi) in a spectral range of the plasmonic spectral feature (SC), is wavelength shifted.

4. Plasmonic biosensor device (1) according to claim 3, wherein the sensing surfaces (17) are disposed on the plasmonic biosensor device (1) to receive, directly or indirectly on the sensing surface (17), the at least one of the entity, analyte and substance to change an intensity of the light at the at least one wavelength (refi).

5. Plasmonic biosensor device (1) according to any one of the previous claims 2 to 4, wherein the at least one wavelength ( refi) is at an emission intensity peak value (PK1) or at least one emission intensity peak value (PK1) of the plasmonic spectral feature.

6. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the optical nanoantennas (15) are physically interconnected optical nanoantennas (15), each optical nanoantenna (15) comprises oris made of at least one metal, and the plurality of optical nanoantennas (15) are interconnected by at least one interconnection (25) comprising or being made of the same at least one metal.

7. Plasmonic biosensor device (1) according to claim 6, wherein the plasmonic structure (11) includes a plurality of interconnections (25) electrically and physically interconnecting the plurality of optical nanoantennas (15), wherein the optical nanoantennas (15) extend in a first elongated direction and the plurality of interconnections (25) extends in a second elongated direction different to the first elongated direction.

8. Plasmonic biosensor device (1) according to claim 7, wherein the second elongated direction is traverse to the first elongated direction.

9. Plasmonic biosensor device (1) according to claim 7 or8, wherein a length (La) of the optical nanoantenna (15) extending in the first elongated direction is greater than a width (Wa) of interconnection (25) extending in a direction traverse to the first elongated direction.

10. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plasmonic structure (11) includes a plurality of interconnections (25) electrically and physically interconnecting the plurality of optical nanoantennas (15), wherein the plurality of interconnection (25) and the plurality of nanoantennas (15) extend to form or define a mesh structure of interlinked optical nanoantennas (15).

11. Plasmonic biosensor device (1) according to claim 10, wherein the interconnections (25) and the optical nanoantennas (15) comprise or are made of the same at least one metal.

12. Plasmonic biosensor device (1) according to any one of the previous claims, wherein a length (La) of the optical nanoantenna (15) extending in an elongated direction of extension of the optical nanoantenna is between 10 and 10000 times greater than a width (Wa) of the optical nanoantenna (15) extending traverse to the elongated direction of extension.

13. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the first electrode (3), the at least one charge carrier tunnelling junction (7) and the second electrode (5) form a multilayer device and / or a superposed stacked layer device to define or form a planar device geometry.

14. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the at least one charge carrier tunnelling junction (7) is a planar tunnelling junction and the plurality of optical nanoantennas (15) are superposed thereon to extend across the at least one charge carrier tunnelling junction (7).

15. Plasmonic biosensor device (1) according to any one of the previous claims, wherein plasmonic structure (11) defines or forms a plasmonic metasurface (21), and the plasmonic structure (11) is configured to generate plasmonic surface lattice resonances.

16. Plasmonic biosensor device (1) according to any one of the previous claims, wherein plasmonic structure (11) defines or forms a plasmonic metasurface (21), and the plasmonic structure (11) is configured to generate plasmons.

17. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plasmonic structure (11) defines or forms an electric contact with the at least one charge carrier tunnelling junction (7) and defines or forms at least one optical interface for light emission, wherein electroluminescent light emission and plasmon generation are produced by charge carriers provided by the at least one charge carrier tunnelling junction (7) by inelastic tunnelling in the at least one charge carrier tunnelling junction (7).

18. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the second electrode (5) is in electrical connection with the at least one charge carrier tunnelling junction (7) to generate charge carriers by charge carrier tunneling in the at least one charge carrier tunnelling junction (7), and the second electrode (5) generates and emits the light emission and luminesce emission spectrum of the plasmonic biosensor device (1).

19. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the optical nanoantennas (15) or each optical nanoantenna (15) is an optically resonant nanoantenna supporting a resonant mode at an optical frequency, and wherein the optical nanoantennas (15) or each optical nanoantenna (15) has an optical sub-wavelength dimension at a wavelength corresponding to a resonant mode optical frequency of the optical nanoantenna (15).

20. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plasmonic structure (11) and the plurality of optical nanoantennas (15) are configured to generate plasmonic surface lattice resonances providing electric field localization and enhancement at a sensing surface of the plasmonic structure (11) and the optical nanoantennas (15).21 . Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plasmonic structure (11) and the plurality of optical nanoantennas (15) are configured to generate plasmons providing electric field localization and enhancement at a sensing surface of the plasmonic structure (11) and the optical nanoantennas (15).

22. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plasmonic structure (11) and the plurality of optical nanoantennas (15) are configured to generate counter-propagating plasmonic lattice modes in the plasmonic structure (11) to provide an optical band gap in a spectral region of the electroluminescence of the plasmonic biosensor device (1).

23. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plurality of optical nanoantennas (15) are arranged in at least two orthogonal directions with differing periodicities to generate at least one plasmonic lattice mode across the at least one charge carrier tunnelling junction (7).

24. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the plasmonic structure (11) includes a plurality of intersections (25) electrically interconnecting the plurality of optical nanoantennas (15), wherein optical nanoantennas (15) of the plurality of optical nanoantennas (15) extend in a first direction and the plurality of intersections (25) extends in a second direction different to the first direction.

25. Plasmonic biosensor device (1) according to the previous claim, wherein the plasmonic structure (11) includes a plurality of arrays (PH1, PH2, PV1 , PV2) of physically interconnected optical nanoantennas (15) physically interconnected by the plurality of intersections (25), the arrays (PH1 , PH2, PV1 , PV2) extending in the first and second directions.

26. Plasmonic biosensor device according to the previous claim, wherein the plasmonic structure (11) includes a plurality of arrays (PH1 , PH2) of optical nanoantennas (15) extending in the first direction, the optical nanoantennas (15) of the arrays (PH1 , PH2) extending in thefirst direction being periodically located on the at least one charge carrier tunnelling junction (7), and the plasmonic structure (11) includes a plurality of arrays (PV1 , PV2) of optical nanoantennas (15) extending in the second direction, the optical nanoantennas (15) of the arrays (PV1 , PV2) extending in the second direction being periodically located on the at least one charge carrier tunnelling junction (7).

27. Plasmonic biosensor device according to the previous claim, wherein a periodic separation distance (prh) of the optical nanoantennas (15) of the array (PH1 , PH2) extending in the first direction is greater than a periodic separation distance (prv) of the optical nanoantennas (15) of the array (PV1 , PV2) extending in the second direction.

28. Plasmonic biosensor device (1) according to any one of the previous claims, wherein the at least one charge carrier tunnelling junction (7) is an electron tunnelling insulator junction, wherein the first electrode (3) comprises at least one metal, the second electrode (5) comprises at least one metal, and the at least one charge carrier tunnelling junction (7) comprises at least one insulator.

29. Plasmonic biosensor device (1) according to the previous claim, wherein the at least one charge carrier tunnelling junction (7) includes a single tunnelling insulator layer in which or through which electron tunneling occurs.

30. Plasmonic biosensor device (1) according to the previous claim, wherein the single tunnelling insulator layer comprises aluminum oxide (AI2O3).

31. Plasmonic biosensor device (1) according to the previous claim, wherein the single tunnelling insulator layer has a thickness less than 7.5nm.

32. Plasmonic biosensor device (1) according to claim 28, wherein the at least one charge carrier tunnelling junction (7) is an electron tunnelling insulator junction located between the first and second electrodes (3, 5), and the at least one charge carrier tunnelling junction (7) includes a layer comprising aluminum oxide (AI2O3), the layer having a thickness less than 7.5nm.

33. Plasmonic biosensor device (1) according to claim 28, wherein the at least one charge carrier tunnelling junction (7) is an electron tunnelling insulator junction located between the first and second electrodes (3, 5), and the at least one charge carrier tunnelling junction (7),in which or through which electron tunneling occurs, consists of a single layer comprising aluminum oxide (AI2O3).

34. Plasmonic biosensor device (1) according to the previous claim, wherein the at least one charge carrier tunnelling junction (7) includes at least one insulator layer comprising aluminum oxide (AI2O3), and the first electrode (3) comprises aluminum.

35. Plasmonic biosensor device (1) according to any one of the previous claims 28 to 34, wherein the at least one charge carrier tunnelling junction (7) is a non metallic-quantum-well tunnelling junction.

36. Sensing method including:providing at least one plasmonic biosensor device (1) according to any one of the previous claims;providing at least one sample for analysis or investigation to the at least one plasmonic biosensor device (1), the sample including at least one of an entity, analyte and substance; and- generating light emission by the at least one plasmonic biosensor device (1).

37. The method of the previous claim, including measuring the generated light emission to determine a wavelength shift of at least one spectral portion of the generated luminesce emission spectrum of the plasmonic biosensor device (1) when the at least one sample for analysis or investigation is provided compared to prior to the provision of the at least one sample for analysis or investigation.

38. The method of the previous claim, including measuring the generated light emission to determine a wavelength shift of a plasmonic spectral feature (SC) of the generated luminesce emission spectrum.

39. The method according to claim 38, wherein the wavelength shift is determined at at least one wavelength (refi) in the spectral range of the plasmonic spectral feature.

40. The method of any one of the previous claims 36 to 39, including measuring the generated light emission to determine a change in light intensity of at least one spectral portion of the generated luminesce emission spectrum of the plasmonic biosensor device (1) when the at least one sample for analysis or investigation is provided compared to prior to the provision of the at least one sample for analysis or investigation.

41. The method of the previous claim, including measuring the generated light emission to determine the change in light intensity of a plasmonic spectral feature (SC) of the generated luminesce emission spectrum.

42. The method of the previous claim, including measuring the generated light emission to determine the change in light intensity at at least one wavelength (refi) of the plasmonic spectral feature (SC).

43. Plasmonic biosensor device (1) according to any one of the previous claims 38 to 40, wherein the at least one wavelength (refi) is at an emission intensity peak value (PK1) or at least one emission intensity peak value (PK1) of the plasmonic spectral feature (SC).

44. The method of the previous claim 41 , including measuring the generated light emission to determine the change in light intensity in a wavelength window or range (window) of the plasmonic spectral feature (SC).

45. The method of the previous claim, wherein the change in light intensity in the wavelength window or range (window) of the plasmonic spectral feature (SC) comprises determining or calculating at least a differential between (i) light intensity in the wavelength window or range (^window) when the at least one sample for analysis or investigation is provided and (ii) light intensity in the wavelength window or range (window) prior to the provision of the at least one sample for analysis or investigation.

46. The method of the previous claim, wherein an average value is determined by averaging the determined differential over wavelength values of the wavelength window or range

Images