Enhanced detection integrated infrared spectroscopy chip based on tunable surface plasmons

Abstract

An integrated infrared spectroscopy chip for enhanced detection based on tunable surface plasmons consists, from top to bottom, of a source and drain, a graphene / boron nitride heterojunction, a nanogap layer, a dielectric metasurface, a dielectric layer, an infrared detector, and a substrate. A nanogap layer exists between the dielectric metasurface and the graphene / boron nitride heterojunction. The dielectric metasurface serves as the gate. The source and drain are evaporated on the surface of the graphene / boron nitride heterojunction, forming a tunable surface plasmon waveguide resonator. The infrared detector is vertically integrated with the tunable surface plasmon waveguide resonator via the dielectric layer for infrared spectral signal detection. Under infrared light irradiation, low-loss surface plasmon modes are excited. The resonant peak is manipulated by an external electric field to achieve wide-band wavelength scanning. Infrared spectral signals are sequentially acquired in a time series. Through processing, the infrared spectral absorption signals of molecules are obtained, ultimately realizing an integrated infrared spectroscopy chip for both spectral enhancement and spectral detection. The present invention offers advantages such as high sensitivity, wide range of detectable substances, compact size, and high integration.

Description

Technical Field

[0001] The present invention relates to the field of infrared spectrum technology, and in particular to an infrared spectrum detection chip integrating spectrum enhancement and spectrum detection. Background Art

[0002] Infrared spectroscopy can directly detect molecular vibrational modes. It offers unique advantages, including high "fingerprint" characteristics, no sample labeling, non-destructive in situ detection, and qualitative and quantitative analysis. It is a highly promising on-site rapid spectroscopy technology, widely used in biomedicine, environmental monitoring, food safety testing, chemical composition analysis, explosives detection, and other critical fields related to national economy and livelihoods. However, traditional infrared spectroscopy suffers from low sensitivity, making it incapable of detecting low concentrations of biomolecules. The primary reason for this is that the wavelength of mid-infrared light (6–16 μm) is three orders of magnitude larger than the molecular size (<10 nm), resulting in extremely weak interactions between light waves and molecules, making infrared spectroscopy signals extremely difficult to detect.

[0003] In recent years, surface-enhanced infrared spectroscopy technology developed based on the surface plasmon effect can excite highly localized electromagnetic resonance modes around molecules, confine light waves in nanospace, and thus greatly enhance the interaction between light waves and molecules. This technology provides a new approach to solving the problem of extremely weak interactions between light waves and molecules and breaking through the technical bottleneck of low detection sensitivity of infrared spectroscopy systems. It has rapidly developed into a research hotspot in cutting-edge interdisciplinary fields such as micro-nano optics, nanotechnology, and life sciences. At present, the primary problem that this technology needs to solve is to study the excitation mechanism of high-intensity localized electromagnetic modes and their interaction with molecular vibration modes to achieve a significant enhancement of molecular infrared absorption spectrum signals. Based on a search of the current research status at home and abroad, there are currently two main solutions:

[0004] The first approach is based on the metal surface plasmon effect, using a metal surface plasmon device in conjunction with a Fourier transform infrared spectrometer to detect spectral signals. By designing various metal nanostructures to generate high-intensity localized electromagnetic modes around molecules, high-precision detection of specific trace molecules is achieved. However, the resonant frequency of metal surface plasmons is in the ultraviolet and visible light bands, and the energy loss of metal surface plasmons in the infrared band is severe. The loss and bandwidth limitations of metal materials are determined by the inherent characteristics of the metal free electron gas, resulting in the inability to dynamically tune the resonant frequency and a narrow infrared spectral enhancement band.

[0005] The second approach is to enhance the infrared absorption spectrum of molecules using the surface plasmon effect of graphene. Spectral signal detection is achieved by combining a surface plasmon device with a Fourier transform infrared spectrometer. Graphene, a novel two-dimensional crystalline material composed of carbon atoms, can support intrinsic localized electromagnetic modes of surface plasmons in the infrared band. These modes exhibit extremely low loss, extremely high local enhancement, and tunable resonant frequency. By adjusting an external voltage to alter the plasmon frequency of the graphene nanostructure, high-precision infrared vibrational information of biomolecules such as proteins can be detected.

[0006] However, graphene surface plasmon devices still commonly suffer from large plasmon resonance peak linewidths and low quality factors. This leads to challenges with current graphene surface plasmon-enhanced infrared spectroscopy techniques, such as low enhancement multiples and spectral resolution. This often requires coupling with a Fourier transform infrared spectrometer to obtain infrared absorption spectrum signals of molecules. Due to the large size, weight, and high cost of traditional Fourier transform infrared spectrometers, this spectral detection method's heavy reliance on infrared spectrometers has severely hindered its rapid on-site detection applications. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention proposes an integrated infrared spectroscopy chip for enhanced detection based on tunable surface plasmons. The chip adopts a graphene / boron nitride heterojunction and a dielectric metasurface composite to design a tunable surface plasmon waveguide resonator, excites a low-loss surface plasmon mode, and realizes narrowband filtering and molecular infrared absorption spectrum enhancement. The tunable surface plasmon waveguide resonator is monolithically integrated with an infrared detector, and the resonance peak is regulated by an external electric field to achieve wide-band wavelength scanning. Infrared spectral signals are obtained in sequence in a time series, and finally the molecular infrared absorption spectrum signal enhancement and detection are realized. The chip has the advantages of ease of use, high sensitivity, high integration, and the ability to detect a variety of unknown trace molecules. It can be used in biomedicine, environmental monitoring, food safety and other fields.

[0008] In order to solve the technical problem of the present invention, the technical solution adopted is:

[0009] The invention relates to an integrated infrared spectroscopy chip for enhanced detection based on tunable surface plasmons. The chip is provided with a source and a drain, a graphene / boron nitride heterojunction, a nanogap layer, a dielectric metasurface, a dielectric layer, an infrared detector and a substrate in sequence from top to bottom.

[0010] The dielectric metasurface is created by depositing a silicon layer on a dielectric layer and then further processing the silicon layer to form the metasurface's structural profile. This dielectric metasurface structure is used to achieve wave vector matching between surface plasmon modes and free-space light. This dielectric metasurface also serves as a back electrode for electrical control of graphene. Compared to metallic metasurfaces, using a dielectric metasurface can effectively reduce losses and improve the quality factor (Q) of the spectrum.

[0011] The graphene / boron nitride heterojunction is a composite of a boron nitride film and a graphene film, which is used to reduce the influence of the substrate on the properties of the graphene material and obtain a low-loss surface plasmon mode.

[0012] A nanogap layer is provided between the dielectric supersurface and the graphene / boron nitride heterojunction, the nanogap layer serving as a gate dielectric layer, and the graphene / boron nitride heterojunction and the dielectric supersurface form a structure similar to a parallel plate capacitor.

[0013] The source and drain are deposited on the graphene / boron nitride heterojunction, and the source and drain are connected through the graphene.

[0014] The dielectric layer is located between the infrared detector die and the dielectric metasurface, that is, located on the infrared detector as a protective layer, used to protect the surface of the infrared detector die and prevent subsequent micro-nano processing from causing damage to the infrared detector die.

[0015] The infrared detector is located on a substrate and is longitudinally monolithically integrated with a tunable surface plasmon waveguide resonator formed by a dielectric layer, the graphene / boron nitride heterojunction, the nanogap layer, and the dielectric metasurface. The detector is used for infrared spectral signal detection. The detection integrated signal is denoised and demodulated using a spectral reconstruction algorithm to obtain the infrared spectral absorption signal of the molecule. Trace molecules are detected based on the obtained spectral information.

[0016] In the above structure of the present invention, the graphene / boron nitride heterojunction, the nanogap layer, and the dielectric metasurface form a tunable surface plasmon waveguide resonator, which can generate tunable surface plasmons under infrared light excitation, thereby generating a strong localized electric field on the graphene surface. Furthermore, by applying an external voltage between the graphene / boron nitride heterojunction and the dielectric metasurface, the surface conductivity of the graphene is adjusted, thereby dynamically adjusting the surface plasmon resonance peak and achieving narrowband filtering. At the same time, when the surface plasmon resonance frequency is tuned to coincide with the molecular vibration frequency of the substance to be detected, the electromagnetic field intensity per unit space around the detected molecule reaches its maximum, greatly enhancing the infrared spectral signal of the detected molecule.

[0017] Preferably, the external voltage applied between the graphene / boron nitride heterojunction and the dielectric metasurface is in the range of -2 to 2 V, and the graphene surface plasmon resonance peak is dynamically adjusted in the infrared range of 5 to 16 μm.

[0018] The device described above detects electrical signals under different voltage conditions, forms corresponding sets of signals, constructs a numerical calculation model, and converts it into a linear model. The parameters to be solved are obtained through an optimization algorithm. The spectral information is reconstructed based on the optimal values ​​to denoise and demodulate the detection integral signal output by the infrared detector, thereby obtaining the infrared spectral absorption signal of the molecule. The obtained spectral information is then used to detect trace molecules.

[0019] Furthermore, the metasurface structure of the dielectric metasurface adopts a periodic array structure, and has different structural shapes such as rectangular, circular, bow-tie, double bow-tie, concentric ring or cross in the transverse direction of the chip. It can be obtained by electron beam exposure, focused ion beam etching, ultraviolet lithography, laser direct writing and other lithography technologies, combined with electron beam evaporation, magnetron sputtering, thermal evaporation and other methods. The size and period range of the metasurface structure are 0.1μm~1μm, and the thickness range of the metasurface structure is 20~100nm.

[0020] Furthermore, the graphene / boron nitride heterojunction is obtained by vertically stacking a boron nitride film and a graphene film in multiple layers, with the number of stacked layers being 1 to 5. The boron nitride is located at the bottom layer of the heterojunction and contacts the nanogap layer, and the graphene is located at the top layer of the heterojunction and contacts the source and drain. It can be prepared by a mechanical stripping process or a chemical vapor deposition method, and the number of layers of the heterojunction film can be achieved by multiple transfer methods.

[0021] Furthermore, the nanogap layer between the graphene / boron nitride heterojunction and the dielectric metasurface has a thickness in the range of 2-20 nm and is made of an infrared transparent material selected from the group consisting of Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, and SiO2.

[0022] Furthermore, the thickness of the dielectric layer on the infrared detector is in the range of 100-500 nm, which is used to protect the infrared detector bare chip. The material of the dielectric layer is an infrared transparent material selected from: Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, SiO2.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] First, graphene, a two-dimensional electron gas composed of a single layer of carbon atoms, supports the propagation of surface plasmons in the infrared band. By tuning its resonant wavelength to align with the vibrational frequency of the molecule being measured, the interaction between trace molecules and light can be greatly enhanced. Furthermore, graphene has a large specific surface area and excellent biocompatibility, enabling the effective adsorption of biomolecules onto its surface.

[0025] Second, the present invention utilizes the composite method of graphene / boron nitride heterojunction and dielectric metasurface to effectively avoid the large number of boundaries and defects introduced by graphene nanopatterning, thereby increasing the lifetime of graphene free carriers, thereby increasing the lifetime of graphene surface plasmons and effectively reducing optical losses. Figure 5 As shown, the use of graphene / boron nitride heterojunction can excite lower and lower-loss surface plasmon modes, obtaining plasmon resonance peaks with higher excitation efficiency and narrower linewidth, thereby improving the coupling efficiency between the surface plasmon resonance mode and the molecular vibration mode during application and enhancing detection sensitivity.

[0026] Third, the graphene / boron nitride heterojunction, nanogap layer, and dielectric metasurface designed in the present invention are combined to form a tunable plasmon waveguide resonator, which can obtain a plasmon resonance peak with a narrower linewidth. By applying an external bias voltage, the conductivity of the graphene surface can be adjusted, and the plasmon resonance wavelength of the graphene surface can be dynamically tuned over a wide band to achieve narrowband filtering in the infrared band.

[0027] Fourth, existing graphene surface plasmons usually need to be used in conjunction with a Fourier infrared spectrometer to obtain the infrared absorption spectrum signal of molecules. Due to the shortcomings of traditional Fourier infrared spectrometers such as large size, large weight, and high price, this technology has been hindered from moving from laboratory sampling analysis to on-site rapid detection. In order to solve this problem, the present invention proposes a monolithic integrated structure of a tunable surface plasmon waveguide resonator and an infrared detector, which does not rely on traditional optical interference structures, frequency scanning and spectroscopic components, and constructs an integrated infrared spectrum chip for enhancement and detection, greatly enhancing the infrared absorption spectrum signal of molecules, and realizing "spectral enhancement" and "spectral detection" on the same device. The present invention can realize wavelength scanning by regulating the resonant peak of the resonator through an external electric field, and denoise and demodulate the detection integral signal through a spectral reconstruction algorithm to obtain the infrared spectrum absorption signal of the molecule, thereby realizing molecular detection without the use of a traditional Fourier infrared spectrometer, and can be used for on-site rapid detection.

[0028] It can be seen that the present invention can simultaneously realize "spectral enhancement" and "spectral detection" of molecular infrared absorption signals, and has the advantages of high sensitivity, wide-band dynamic tunability, small size, easy integration, etc., and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of an integrated infrared spectroscopy chip for enhanced detection;

[0030] Figure 2(a)-Figure 2(f) Schematic diagram of an antenna array of a dielectric metasurface in the shape of a rectangle, circle, bow-tie, double bow-tie, concentric ring or cross;

[0031] Figure 3 A magnified longitudinal cross-section of the dielectric metasurface;

[0032] Figure 4 Flowchart of the preparation method of the integrated infrared spectroscopy chip for enhanced detection;

[0033] Figure 5 Infrared absorption spectra of graphene / boron nitride heterojunction and different graphene electron relaxation times;

[0034] Figure 6 Enhanced detection of infrared absorption spectra of the integrated infrared spectrum chip under different voltage conditions;

[0035] Figure 7 To enhance the detection of reconstructed infrared spectrum signals after the integrated infrared spectrum chip adsorbs probe molecules;

[0036] Figure 8 To enhance the detection of molecular infrared absorption spectra detected by integrated infrared spectroscopy chips; DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, preferred embodiments of the present invention are described in further detail below with reference to the accompanying drawings, in which the same reference numerals represent the same or similar components.

[0038] See also Figure 1 The integrated infrared spectroscopy chip for enhanced detection based on tunable surface plasmons designed in the present invention comprises a substrate 1, an infrared detector 2, a dielectric layer 3, a dielectric metasurface 4, a nanogap layer 5, a graphene / boron nitride heterojunction 6, a source 7, and a drain 8, which are arranged in sequence from bottom to top. During testing, the molecule to be tested 10 is placed on the chip by spraying, spin coating, drop coating, etc. Among them, the infrared detector 2 is located on the substrate 1, the dielectric layer 3 is located on the infrared detector 2, the dielectric metasurface 4 is also located on the dielectric layer 3 as a gate, the graphene / boron nitride heterojunction 6 is located on the nanogap layer 5, the source 7 and the drain 8 are deposited on the graphene / boron nitride heterojunction 6, and the source 7 and the drain 8 are connected through the graphene / boron nitride heterojunction 6.

[0039] In the above structure, a nanogap layer 5 is placed between the dielectric metasurface 4 and the graphene / boron nitride heterojunction 6, forming a tunable surface plasmon waveguide resonator for exciting infrared surface plasmons. This structure also forms a structure similar to a parallel plate capacitor. By applying an external voltage through a voltage source 9 between the graphene / boron nitride heterojunction 6 and the dielectric metasurface 4, the graphene's Fermi level is modulated, thereby achieving control of the plasmon resonance peak. The nanogap layer 5 has a thickness ranging from 2 to 20 nm and is made of an infrared-transparent material, which can be selected from: Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, and SiO2.

[0040] Dielectric layer 3 is located on infrared detector 2 and is used to prevent direct contact between dielectric metasurface 4 and infrared detector 2, thereby protecting the bare die of infrared detector 2. Dielectric layer 3 has a thickness ranging from 100 to 500 nm and is made of an infrared-transparent material, which can be selected from: Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, and SiO2.

[0041] Infrared detector 2 is fabricated on substrate 1 via vacuum coating and molecular beam epitaxy. Available detector types include mercury cadmium telluride (HgCdTe) infrared detectors, type II superlattice infrared detectors, and pyroelectric infrared detectors. Metal electrodes are fabricated via vacuum thermal evaporation. The infrared detector is connected to an external circuit using wires attached to the metal electrodes. In this way, infrared detector 2 is vertically integrated with a tunable surface plasmon waveguide resonator via dielectric layer 3 for infrared spectral signal detection. A spectral reconstruction algorithm is used to denoise and demodulate the integrated detection signal to obtain the molecular infrared spectral absorption signal. This spectral information enables detection of trace molecules.

[0042] See Figure 2 and Figure 3 The structural shape of the dielectric metasurface 4 can be various, including Figure 2 (a) rectangle, 2 (b) circle, 2 (c) bow-tie, 2 (d) double bow-tie, 2 (e) concentric ring or 2 (f) cross, etc. The size and period of these antenna structures range from 0.1 μm to 1 μm, and the thickness ranges from 20 to 100 nm. They can be prepared by electron beam exposure, focused ion beam etching, ultraviolet lithography, laser direct writing and other lithography techniques, combined with electron beam evaporation, magnetron sputtering, thermal evaporation and other methods.

[0043] The present invention sandwiches a nanogap layer 5 between a graphene / boron nitride heterojunction 6 and a dielectric metasurface 4, and excites surface plasmons in the graphene / boron nitride heterojunction 6 through the dielectric metasurface 4, thereby generating a strong localized electric field on the graphene surface in the graphene / boron nitride heterojunction 6. This strong localized electric field couples with the molecular vibration mode, greatly enhancing the infrared absorption signal of the molecule 10 to be measured on the chip surface.

[0044] Figure 4 Detailed processing flow chart for preparing enhanced detection integrated infrared spectrum chip:

[0045] Step S1, preparing an infrared detector: preparing an infrared sensitive material thin film on a substrate 1 by using vacuum coating, molecular beam epitaxy and vacuum thermal evaporation methods to prepare an infrared detector 2.

[0046] Step S2, preparing a dielectric layer: using electron beam evaporation, atomic deposition or molecular beam epitaxial growth methods to prepare a dielectric as a dielectric layer 3 on the surface of the infrared detector, which is used as a protective layer.

[0047] Step S3, preparing the dielectric metasurface 4: depositing a silicon layer on the surface of the dielectric layer 3 by magnetron sputtering, electron beam evaporation, atomic deposition, etc., engraving the structural outline of the metasurface on the deposited silicon layer by electron beam exposure or focused ion beam etching, dry-etching the electron beam exposed structure to obtain the dielectric metasurface structure 4, and using the dielectric metasurface as a gate.

[0048] Step S4, preparing a nanogap layer: using magnetron sputtering, electron beam evaporation, and atomic deposition methods to prepare a dielectric as a nanogap layer 5 on the dielectric metasurface to achieve surface plasmon excitation and gate voltage control.

[0049] Step S5, preparing a boron nitride film: preparing a boron nitride film by using a mechanical stripping process or a chemical vapor deposition method;

[0050] Step S6, preparing a graphene film: preparing a graphene film by using a mechanical exfoliation process or a chemical vapor deposition method;

[0051] Step S7, transferring the graphene / boron nitride heterojunction film: The prepared boron nitride film and graphene film are alternately transferred to the prepared substrate. During the transfer, the boron nitride is located at the bottom of the heterojunction and contacts the nanogap layer, while the graphene is located at the top of the heterojunction and contacts the source and drain electrodes. The number of layers of the graphene / boron nitride heterojunction film 6 ranges from 1 to 5, and a multilayer structure can be achieved through multiple transfers.

[0052] Step S8, preparing the source and drain: using ultraviolet lithography, laser direct writing, and electron beam evaporation to prepare metal contact ohmic electrodes, namely the source 7 and the drain 8, on the graphene / boron nitride heterojunction film 6.

[0053] The tunable surface plasmon waveguide resonator composed of the dielectric metasurface 4, the nanogap layer 5, and the graphene / boron nitride heterojunction 6 can generate surface plasmons under the excitation of infrared light waves, thereby generating strong absorption in the infrared region, such as Figure 3As shown, a strong localized electric field is generated on the graphene surface. Furthermore, an external voltage 9 is applied between the dielectric metasurface 4 and the graphene / boron nitride heterojunction 6 to adjust the graphene's surface conductivity. The external voltage 9 ranges from -2 to 2 V, dynamically adjusting the surface plasmon resonance peak of the graphene / boron nitride heterojunction 6 within the 5-16 μm infrared range.

[0054] like Figure 8 As shown, as the external voltage increases from -0.5V to -2V, the corresponding enhanced resonance peak blue-shifts; when the resonance frequency of the excited graphene surface plasmon is tuned to be consistent with the molecular vibration frequency of the molecule to be detected 10, the electromagnetic field intensity within the unit space around the molecule to be detected reaches the strongest, thereby enhancing the infrared spectrum signal of the molecule to be detected 10.

[0055] The spectral signal is further detected by the infrared detector 2 to obtain the electrical signal detected under different voltage conditions. The spectral reconstruction algorithm is used to realize the denoising and demodulation of the detection integral signal output by the infrared detector. Figure 6 and Figure 7 The infrared spectral signals before and after the adsorption of the probe molecule are reconstructed respectively, and the infrared spectral absorption signal of the molecule to be tested 10 is finally obtained, and the trace molecule is detected according to the obtained spectral information.

[0056] The following further illustrates the principles and intended effects of the present invention with reference to the following embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below, and those skilled in the relevant art may implement the present invention in various forms. The essence of this specification is merely to help those skilled in the relevant art comprehensively understand the specific details of the present invention.

[0057] This embodiment takes a graphene plasmon-enhanced detection integrated chip based on a HgCdTe detector as an example. First, a layer of HgCdTe material is grown on a substrate by vacuum coating and molecular epitaxy to prepare an infrared detector, which is then connected to an external circuit. Second, a layer of aluminum oxide film with a thickness of approximately 200 nm is deposited on the surface of the infrared detector by electron beam evaporation to serve as a dielectric layer to protect the infrared detector. Then, a layer of silicon with a thickness of approximately 30 nm is deposited on the dielectric layer by magnetron sputtering to serve as a gate material to regulate the Fermi level and carrier concentration of graphene and also as a dielectric metasurface material. Focused ion beam etching is then used to prepare a dielectric metasurface structure. The dielectric metasurface structure has a bow-tie shape, a period of 300 nm, a gap of 80 nm, and an overall size of 100 μm × 100 μm. Next, a thin layer of aluminum oxide with a thickness of approximately 10 nm is deposited on the dielectric metasurface structure by atomic layer deposition to prepare a nanogap layer. Further, a single layer of boron nitride (0.1 The boron nitride film and graphene film were sequentially transferred onto a thin layer of aluminum oxide using poly(methyl methacrylate) (PMMA) as a transfer agent. Finally, gold source and drain electrodes were prepared on the graphene / boron nitride heterojunction by UV etching and electron beam evaporation.

[0058] Lattice defects, mechanical damage, and impurity contamination on the detector surface can introduce energy levels into the bandgap, increasing the surface trapped charge density and causing more surface recombination. More injected carriers recombine and disappear on the surface, severely impacting device performance. Therefore, the difficulty in integrating infrared detectors lies in optimizing the device surface passivation process. By depositing or growing a suitable passivation film on the semiconductor surface, dangling bonds on the semiconductor surface can be bound, reducing the surface state density and the surface recombination rate, effectively lowering the device dark current and improving detection performance.

[0059] In the embodiment, biomolecules are used as probe molecules, and a biomolecule film with a thickness of 8 nm is spin-coated on the detection chip. Figure 8The graphs show the chip's infrared absorption enhancement curves for biomolecules under different voltage conditions. As can be seen, the biomolecule's vibrational modes at 6.235μm and 6.355μm are significantly enhanced on the graphene nanoprobe. By increasing the external voltage from -0.5V to -2V, the graphene nanoprobe's infrared resonant frequency blueshifts, enabling selective enhancement of biomolecule vibrational modes. The graph shows that the coupling of biomolecule vibrational modes with the graphene surface plasmon resonant modes results in concave peaks, whose frequencies correspond to the resonant frequencies of the biomolecule's respective vibrational modes. At external voltages of -0.5V and -2V, the graphene nanoprobe's resonant modes are closest to the biomolecule's vibrational frequencies, resulting in the greatest enhancement of these molecular vibrational modes. Calculated enhancement factors for biomolecule infrared spectroscopy signals from the chip can reach up to 100 times.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above embodiments, those skilled in the art should understand that the descriptions and embodiments are merely exemplary and that various changes may be made in form and details. The true scope and spirit of the present invention are defined by the claims.

Claims

1. An integrated infrared spectroscopy chip with enhanced detection based on tunable surface plasmons, characterized by: Including top-down source and drain stages, graphene / boron nitride heterojunction, nanogap layer, dielectric metasurface, dielectric layer, infrared detector and substrate; The dielectric metasurface is obtained by depositing a silicon layer on the surface of a dielectric layer and further performing micro-nano processing on the silicon layer to form a metasurface structural profile, thereby obtaining a dielectric metasurface structure for achieving wave vector matching between surface plasmon modes and free-space light. The graphene / boron nitride heterojunction is a composite structure of a boron nitride film and a graphene film, and is used to reduce the influence of the substrate on the properties of the graphene material, thereby obtaining a low-loss surface plasmon mode; A nanogap layer is provided between the dielectric metasurface and the graphene / boron nitride heterojunction, forming a tunable surface plasmon waveguide resonator. When excited by infrared light waves, tunable surface plasmons are generated, thereby generating a strong localized electric field on the graphene surface. Furthermore, by applying an external voltage between the graphene and the dielectric metasurface, the surface conductivity of the graphene is adjusted, thereby dynamically adjusting the surface plasmon resonance peak to achieve narrowband filtering. Simultaneously, when the surface plasmon resonance frequency is tuned to coincide with the molecular vibration frequency of the substance to be detected, the infrared spectral signal of the molecule to be detected is enhanced. The source and drain are deposited on the graphene / boron nitride heterojunction, and the source and drain are connected through the graphene; The dielectric layer is located between the infrared detector die and the dielectric metasurface and is used to protect the surface of the infrared detector die; The infrared detector die is located on a substrate and is vertically integrated with a tunable surface plasmon waveguide resonator via a dielectric layer for infrared spectrum signal detection.

2. The enhanced detection integrated infrared spectrum chip according to claim 1, characterized in that: The metasurface structure of the dielectric metasurface is rectangular, circular, bow-tie, double bow-tie, concentric ring or cross-shaped in the transverse direction of the chip; the size and period of the metasurface structure range from 0.1 μm to 1 μm, and the thickness of the metasurface structure ranges from 20 to 100 nm.

3. The enhanced detection integrated infrared spectrum chip according to claim 1 or 2, characterized in that: The dielectric metasurface is obtained by utilizing electron beam exposure, focused ion beam etching, ultraviolet lithography, and laser direct writing lithography technology in combination with electron beam evaporation, magnetron sputtering, and thermal evaporation methods.

4. The enhanced detection integrated infrared spectrum chip according to claim 1, characterized in that: The graphene / boron nitride heterojunction is a multi-layer alternating stack of boron nitride films and graphene films in a vertical direction, with the stacking range being 1 to 5 layers. The boron nitride is located at the bottom layer of the heterojunction and contacts the nanogap layer, and the graphene is located at the top layer of the heterojunction and contacts the source and drain electrodes.

5. The enhanced detection integrated infrared spectrum chip according to claim 4, characterized in that: The graphene / boron nitride heterojunction film is prepared by a mechanical exfoliation process or a chemical vapor deposition method, and the number of layers of the heterojunction film is achieved by multiple transfer methods.

6. The enhanced detection integrated infrared spectrum chip according to claim 1, characterized in that: The thickness of the nanogap layer is in the range of 2-20 nm, and the material is an infrared transparent material selected from: Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, and SiO2.

7. The enhanced detection integrated infrared spectrum chip according to claim 1, characterized in that: The thickness of the dielectric layer is in the range of 100-500 nm, and the material is an infrared transparent material selected from: Al2O3, KBr, MgF2, CaF2, BaF2, AgCl, ZnSe, and SiO2.

8. The enhanced detection integrated infrared spectrum chip according to claim 1, characterized in that: The infrared detector has a detection band range of 3-10 μm and is selected from a mercury cadmium telluride infrared detector, a type II superlattice infrared detector, and a pyroelectric infrared detector.

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