Magnetic field sensor

Abstract

The magnetic field sensor 1 includes a substrate 4 having opposing upper and lower surfaces that are electrically inert and optically transparent. A microwave or RF generator element 13 is disposed on the upper side of the substrate, and the generator element 13 is configured to be connected to an electrode for connection to a microwave or RF generator. The sensor 1 includes a heterostructure organic light-emitting diode (OLED) 2 disposed adjacent to the microwave or RF generator element 6, the heterostructure organic light-emitting diode (OLED) 2 being configured to be connected to a first electrode and a second electrode.

Description

Technical Field

[0001] The present invention relates to magnetic field sensing, and more particularly, to an optically readable low-intensity magnetic field sensor.

[0002] Preferred embodiments of the present invention are described in connection with the detection of low magnetic field intensities resolved in two-dimensional space, but it will be understood that the present invention is not limited to this particular application example and may also spatially resolve low magnetic field intensities in one or three dimensions.

Background Art

[0003] Quantum sensing and imaging of magnetic fields have attracted wide interest due to their potential for high sensitivity and spatial resolution. Common quantum sensing techniques require either optical excitation (e.g., diamond nitrogen vacancy centers, atomic vapor magnetometers) or cryogenic temperatures (e.g., SQUIDs, superconducting qubits), which pose challenges for chip-scale integration and commercial scalability.

[0004] Magnetic field sensing and mapping are important for many scientific and technical applications across both physical and biological systems. Quantum sensing techniques have decisive advantages compared to classical methods, including high sensitivity in magnetic field detection and high spatial resolution in magnetic field mapping. Among many quantum techniques, the diamond nitrogen vacancy (NV) center has emerged as an excellent sensor platform, demonstrating room-temperature picotesla-level sensitivity, nanoscale spatial resolution, and good integration and miniaturization.

[0005] On the other hand, organic semiconductors (OSCs) are very sensitive to magnetic fields. It has been proven that solid-state devices based on OSC have been proposed as a new type of quantum sensor. Unlike NV-based techniques, magnetic sensors based on OSC do not require optical pumping. Furthermore, both electrical readout and optical readout can be provided through optically detected magnetic resonance (ODMR) and electrically detected magnetic resonance (EDMR). EDMR enables chip-scale integration of single-point sensors. Furthermore, ODMR enables simultaneous acquisition of multiple optical signals within the field of view, enabling spatial resolution sensing and spatial resolution imaging. OSC is also inherently compatible with mass-produced household appliances, offering the potential for ubiquitous deployment. Both electrical readout and optical readout can be provided. Chip-scale integration of single-point sensors becomes possible with EDMR. Furthermore, simultaneous acquisition of multiple optical signals within the field of view becomes possible with ODMR, enabling spatial resolution sensing and spatial resolution imaging. OSC is also inherently compatible with mass-produced household appliances, offering the potential for ubiquitous deployment.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a spatially resolved low magnetic field strength detection device that overcomes one or more of the drawbacks of the prior art, or to provide a useful alternative means.

[0007] According to a first aspect of the present invention, there is disclosed a magnetic field sensor comprising a substrate that is electrically inert and optically transparent and has an upper surface and a lower surface, a microwave or radio frequency (RF) generator element disposed on the upper side of the substrate, the microwave or RF generator being configured to be connected to an electrode for connection to the microwave or RF generator, and a heterostructure organic light-emitting diode (OLED) disposed adjacent to the microwave or RF generator and configured to be connected to a first electrode and a second electrode.

[0008] According to a second aspect of the present invention, there is provided a substrate that is electrically inert and optically transparent and has an upper surface and a lower surface One or more spaced-apart substrates, a plurality of spaced-apart microwave or RF generator elements disposed on one substrate, or one or more microwave or RF generator elements disposed on the upper side of each substrate, each configured to be connected to an electrode for connection to a microwave or RF generator, one or more microwave or RF generator elements, and a heterostructure organic light-emitting diode (OLED) disposed adjacent to each microwave or RF generator element, each configured to be connected to a first electrode and a second electrode, a magnetic field sensor is provided.

[0009] According to another aspect of the present invention, a substrate having an upper surface and a lower surface that is electrically inert and optically transparent, a microwave or RF generator element disposed on the upper side of the substrate, the microwave or RF generator configured to be connected to an electrode for connection to a microwave or RF generator, and a plurality of heterostructure organic light-emitting diodes (OLEDs) disposed adjacent to the microwave or RF generator, each configured to be connected to a first electrode and a second electrode, a magnetic field sensor is disclosed.

[0010] Thus, it can be seen that a spatially resolved low magnetic field device that can be disposed on a single chip and does not require optical pumping or cryogenic temperatures is advantageously provided. Further, an OLED-based integrated quantum sensor for magnetic field imaging that employs spatially resolved magnetic resonance to provide a robust mapping of the magnetic field overcomes the important technical problem of having suitable electrical insulation (optical readout) between the resonator and the OLED while integrating the resonator and the OLED on the same substrate. In the preferred embodiments described below, the optical imaging system is about 160 μTHz 1 / 2 μm -2Magnetic field mapping was achieved with the magnetic field sensitivity of . This demonstrates the possibility of a method for magnetic field sensing and magnetic field mapping based on chip-scale OLEDs without using lasers. An array of sensors can be arranged one-dimensionally, two-dimensionally, or three-dimensionally on a single substrate, or across multiple substrates.

Brief Description of the Drawings

[0011] Preferred embodiments of the present invention will be described by way of example only with reference to the accompanying drawings.

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Embodiments for Carrying Out the Invention

[0012] Referring generally to the drawings of the preferred embodiments, like reference numerals are used to indicate like components unless otherwise expressly indicated.

[0013] First, it should be noted that the principles of optical detection magnetic resonance and electrical detection magnetic resonance rely on spin-dependent recombination and dissociation dynamics in OLEDs. When positive and negative charge carriers are injected from the anode and cathode, they first electrostatically combine to form polaron pairs within the light-emitting layer. These polaron pairs can have either singlet-dominant or triplet-dominant characteristics depending on their spin configuration, and transitions occur between them by spin mixing. The polaron pairs can further recombine to form singlet excitons or triplet excitons, or dissociate back into free charge carriers at a rate depending on their singlet-triplet symmetry. Under magnetic resonance (f = γB0, where f is the microwave frequency, γ is the magnetic gyration ratio, and B0 is the applied magnetic field), the spin orientation of the charge carriers in the polaron pair is manipulated, which causes a change in the population ratio between the singlet pair and the triplet pair. The change in population ultimately leads to changes in both electroluminescence (EL) and current through the recombination process and the dissociation process, respectively.

[0014] A preferred embodiment of the present invention provides an integrated semiconductor device 1 for detecting and imaging a magnetic field, in which an OLED 2 and a microwave resonator 3 are laterally integrated on the same substrate 4 (Fig. 1a). The architecture of the device 1 enables the measurement of magnetic fields both electrically (via EDMR) and optically (via ODMR). The device 1 can function not only as a point sensor by measuring bulk EDMR or ODMR spectroscopy, but also as a virtual array of sensors 10 by spatially resolved ODMR. The latter advantageously provides a path to high-speed magnetic mapping without point-to-point scanning by using a camera to generate the virtual array, which may have potential applications in quantum magnetic sensing and quantum magnetic imaging. The generated microwave field of the split-ring resonator is sufficient for spin resonance even when not driven in the resonant state.

[0015] Referring to Fig. 1, the structure of the device 1 is shown. Fig. 1(a) is a photograph of a template based on the microwave resonator 3, in which an omega-shaped resonator element 6 is integrated on a pre-patterned ITO / glass substrate 4. However, it will be understood that in other preferred embodiments the substrate may be a rigid or flexible plastic. Generally, the resonator element 6 can be said to be omega-shaped considering its similarity to the Greek letter Ω, but in a preferred embodiment it is described as a flat ring 7 having an open arc length 8 defining a chord length disposed between respective ends 9 and 10. The ends 9 and 10 of the ring 7 are connected to respective electrodes 11 and 12 of the microwave source 13. It can be seen that the microwave resonator 3 includes the element 6 and the electrodes or legs 11, 12.

[0016] The active region at the center of the ring 7 has a diameter of 80 μm and is defined by photolithography and deposition of an insulating layer. The inset shows I = 500 nA (about 10 mA / cm 2Figure showing a photograph of the integrated OLED2 in the current corresponding to the current density. Fig. 1(b) shows a schematic diagram of the structure and experimental measurement configuration of the integrated device 1 employed together with the AC magnetic field B1 generated by the microwave resonator 3 and the static magnetic field B0 generated by an external electromagnet 14 (not shown in Fig. 1b).

[0017] Fig. 1(c) shows a conventional EDMR spectrum where the static magnetic field B0 is swept at a fixed microwave frequency of 710 MHz. This spectrum is well described by the sum (black) of two Gaussian functions (red, blue) corresponding to two hyperfine magnetic field distributions (σ1 = 0.18(2), σ2 = 0.94(2)) received by the electron spin and the hole spin respectively. σ1 and σ2 represent the standard deviations of the two Gaussian functions. Fig. 1(d) shows the frequency-swept EDMR spectrum, where the microwave frequency is swept by fixing the current in the electromagnet 14 to a fixed magnetic field

[0018]

Number

[0019] Figs. 7 and 8 show the "wobbling" characteristic noise in the raw magnetic resonance spectrum with the microwave frequency swept. This noise is due to the S 11Since a similar "wobbling" feature is seen in the curve (see Fig. 7(a)), it is considered to originate from the microwave component in the experimental setup. This wobbling may be due to the mismatch of the 50Ω impedance of the RF output, resulting in some end reflection of the signal in cable 16. Fig. 7(b) shows the microwave resonator 3 connected to the microwave source 13 via the PCB. Then, such noise is transmitted and deformed through the PCB and the resonator, and finally coupled to the OLED2, bringing such "wobbling" feature noise to the final EDMR spectrum (see Fig. 8). Furthermore, the amplitude of the noise is not constant and varies at different microwave frequencies (see Fig. 3). Such baseline noise can be measured separately and then subtracted from the data. Fig. 8 shows the raw signals and background noise of the x-channel in Fig. 8(a) and the y-channel in Fig. 8(b) in lock-in detection where the microwave frequency is swept. The signals of the x-channel in (a) and the y-channel in (b) after the noise is subtracted. The final EDMR signal is

[0020]

Number

[0021] The structure of device 1 consists of two main components: an omega-shaped microwave resonator 3 with an element 6 having electrodes 11, 12, and a micrometer-sized heterostructure OLED2 located at the center of the resonator 3 (Fig. 1b). The microwave resonator 3 is electrically insulated from the OLED2 by employing two insulating layers between them (further explained below). Fig. 1(a) shows the resonator integration template on the substrate 4 before including the OLED2, and the inset shows the completed device where the OLED2 is lit or turned on with bright and uniform electroluminescence at a current I = 500 nA. The EDMR characteristics of device 1 were first tested. Fig. 1(c) shows the case where the microwave frequency is fixed (71 shows a typical EDMR spectrum with the external magnetic field B0 swept at 0 MHz. The EDMR signal (current change) coincides well with the magnetic resonance condition and

[0022]

Number

[0023] To measure the externally applied magnetic field B0, the microwave frequency is swept while simultaneously monitoring the current change by lock-in detection 17. The change in current is measured as a function of the microwave frequency, reaches its maximum value at the resonance frequency, and from there the external magnetic field can be easily determined as B0 = f / γ. Figure 1(d) shows the frequency-swept EDMR spectrum, where the external magnetic field B0 is fixed at about 25.2 mT and the spectral peak

[0024]

Number

[0025] Furthermore, the magnetic field response of Device 1 has been shown to be linear over more than two orders of magnitude in the frequency domain (40 MHz to 6.0 GHz). The upper limit of the resonance frequency is purely limited by the microwave source 13, and much higher resonance frequencies can be achieved using a suitable microwave source (not shown). The minimum detectable magnetic field is limited by the intrinsic ultra-fine magnetic field inside the OSC, which can be compensated by applying an additional static magnetic field by the micro-wire design (not shown). Furthermore, for the detection of extremely small magnetic fields, the influence of the Earth's magnetic field (about 50 μT) on the spin-charge carriers in the OSC should be considered, which may be removed by magnetic shielding.

[0026] To demonstrate the sensing ability of Device 1, a permanent magnet 15 is used to generate a magnetic field. The permanent magnet 15 provides an easy way to generate a wide range of static magnetic fields with a known spatial distribution, which will be further described below.

[0027] Figures 2(a)-(c) and 10 show magnetic field sensing based on EDMR of the preferred embodiment. Figure 2(a) is a schematic diagram of the setup of the preferred embodiment (not to scale). The cylindrical magnet 20 is placed adjacent to Device 1 such that the cylindrical axis of the generated magnetic field is aligned with the plane of the substrate 4 of the device. A 2D simulation of the spatial distribution of the decaying magnetic field strength generated by the cylindrical magnet within a 14.0 mm × 36.0 mm region in the x-y plane at a distance d of about 10.0 mm from the magnet 20. Since the OLED 2 is located at the center of the rectangular glass substrate 4 (see Figure 10) of the device for EDMR measurements based on frequency sweeping, the distance d corresponds to half the width of the device substrate 4.

[0028] In use, first, at the starting position, the edge of the substrate 4 (not clearly shown in Figure 10) and A small gap (x0) was set between the magnet 20 to avoid possible physical contact between them during movement. The total distance between the OLED2 (yellow dot) and the magnet is d + x0. The x - coordinate and y - coordinate represent the horizontal movement direction and the vertical movement direction within the laboratory frame, respectively. The OLED2 functions as a point detector for measuring the magnetic field strength generated by the magnet 20, and x0 represents the starting position of the measurement. Fig. 2(b) shows the magnetic field detected when the device 1 is stepped along the x - axis. The magnetic field strength is measured via the frequency - swept EDMR spectrum at each position, and the solid - line curve is a simulation using the estimated starting position of x0~0.20 mm. Fig. 2(c) shows the magnetic - field detection when the device 1 is stepped along the y - axis at the estimated starting position of x0~0.40 mm.

[0029] Fig. 10 shows the experimental setup where the magnet 20 is placed next to the device 1 and the OLED2 operates as a point sensor of the magnetic field via frequency - swept EDMR measurement. In OSC, the resonance peak frequency of the EDMR spectrum depends only on the intensity rather than the direction of the external magnetic field B0, and this direction - independent characteristic is also observed in the device 1 (to be further explained elsewhere). Two independent measurements are carried out, and the device 1 (as a point sensor) is stepped separately along the x - direction (horizontal) and y - direction (vertical). At each step of the movement, the microwave frequency is swept, and the magnitude of B is determined from the resonance frequency of the resulting EDMR spectrum. The measurement results show that the sensor can detect the magnetic field with high precision over a wide range, and the similarity between the experimental results and the computational simulations is approximately 99.8% (Fig. 2b) and 98.6% (Fig. 2c), respectively.

[0030] Specifically, to verify that the magnetic resonance conditions do not depend on the orientation of the external magnetic field B0 within device 1, separate angle-dependent EDMR measurements are performed. As demonstrated in FIGS. 9(a) and (b), device 1 is mounted on a rotating stage 21 positioned between two electromagnet poles 14 (see FIG. 9). Instead of changing the orientation of magnetic field B0, the orientation of microwave field B1 is equivalently changed. As device 1 rotates, the orientation of microwave field B1 rotates within the horizontal x-y plane, which is indicated by angle θ as shown in FIG. 9(a). The following was found: (1) The amplitude of the EDMR spectrum peak corresponding to the maximum change in the EDMR signal is proportional to the projection of the B1 magnetic field along the direction orthogonal to B0, and the relationship between the amplitude and the rotation angle can be well fitted by a sine wave function. (2) The resonance frequency (f = B0 x γ) of the EDMR spectrum peak corresponding to the external magnetic field B0 remains the same with a confidence level of 99.94%.

[0031] FIG. 9(a) shows the rotation method where B0 is a static magnetic field generated by two electromagnet poles with a fixed orientation, and B1 is an oscillating field generated by the integrated microwave resonator 3 on device 1. The orientation of magnetic field B1 rotates within the horizontal x-y plane as the stage rotates. FIG. 9(b) is a photograph of the experimental setup. Device 1 is vertically mounted on a PCB, and the PCB is mounted on a rotating stage. FIG. 9(c) shows the amplitude of the resonance peak of the EDMR spectrum as a function of the rotation angle θ, where the frequency of microwave field B1 is fixed at 700 MHz and magnetic field B0 is swept. FIG. 9(d) shows the difference in the resonance B0 field between the experimental values extracted from the EDMR spectrum and the theoretical values calculated by B0 = f / γ, where f = 700 MHz and γ = 28.03 (GHz / T). The error bars correspond to the magnetic field step accuracy (0.02 mT) in this measurement.

[0032] Very small EDMR signals were observed at θ = 90° and θ = 270°, which are due to spatial variations in the microwave field. The distance between the microwave element 6 and the OLED 2 is much shorter than the wavelength of the microwave radiation, and thus, the OLED 2 is in the near-field region of the B1 magnetic field. As a result, the spatial orientation of the B1 magnetic field is determined by the dimensions of the resonator 3 itself and the surrounding conductors, and this orientation varies slightly within the OLED 2 region. Therefore, a small in-plane projection (B 1 / / ) of the B1 magnetic field always exists during the entire rotation, which plays a dominant role in the non-zero EMDR spectrum at θ = 90° and θ = 270°.

[0033] Small variations in the resonant B0 threshold value result from the following aspects. (1) The influence of the SMA connector 16A on the PCB. The SMA connector 16A of the SMA cable 16 in the preferred embodiment shows weak paramagnetic behavior under a large external magnetic field and was found to lead to a very weak disturbance to the reading of the Gauss probe 22 during rotation. The disturbance becomes prominent (on the scale of 0.1 mT) at some angles (60° - 120°) where the SMA connector 16 is closest to the Gauss probe 22. Note in Fig. 13(d) that such disturbances have been removed by an independent and careful calibration process. (2) The finite sweep magnetic field step size that makes the B0 value extraction uncertain. (3) The uniformity of the static magnetic field B0 between the two electromagnet poles. The magnetic field uniformity depends on the dimensions of the two poles, the gap between them, and their spatial positions. In practice, the magnetic field detected by the Gauss probe 22 always differs slightly from the actual magnetic field received by the device 1, and such differences can even vary during rotation if the rotation setting is not perfectly aligned with the magnet.

[0034] Regarding spatial resolved ODMR and magnetic field mapping, the integrated device 1 can not only electronically sense the magnetic field via the EDMR method, but also provide optical accessibility for magnetic field mapping via spatial resolved ODMR. To measure the spatial resolved ODMR, an optical microscope 23 (Fig. 3a) is used to image the OLED 2 onto a scientific complementary metal oxide semiconductor (sCMOS) camera 24, although it will be understood that any suitable optical imaging system can also be used.

[0035] Fig. 3(a) is a schematic diagram of the setup for spatial resolved ODMR. The inset shows an image of the EL intensity captured by the sCMOS camera 24. The arrow of the B magnetic field represents the magnetic field gradient across the OLED 2 along the x-axis direction in the horizontal x-y plane.

[0036] Fig. 3(b) shows the manner used for pixel binning in which n×n adjacent camera pixels are integrated into one combined pixel called a "superpixel" via the pixel binning process. The optical signal (EL intensity) of each superpixel is the average of all the signals of the n×n individual camera pixels. Fig. 3(c) shows a double Gaussian fit of the ODMR spectra of two superpixels with a binning size n = 3. Superpixel 1 and Superpixel 2 correspond to the superpixels at positions (-63.4 μm, 0.0 μm) and (52.4 μm, 0.0 μm) in (d), respectively. The black dot dots indicate the resonance peak positions in the fit curve. Fig. 3(d) shows the resonance frequencies (f of the ODMR spectra of 166×166 superpixels with a binning size n = 3 ODMR) is a 2D spatial map. The entire area contains 500×500 pixels, and the superpixel size is approximately 0.91(5) μm × 0.91(5) μm (n = 3). Due to the high hole conductivity of the PEDOT:PSS thin film, a weak EL signal is also observed outside the defined area of OLED2. This provides an ODMR spectrum over the entire area. In Fig. 3(e), the leftmost figure (n = 3) shows an enlarged view of a local area (10×10 superpixels) of the 2D map in Fig. 3(d). The other four figures show magnetic field maps of the same area with different binning sizes.

[0037] As described above, the measurement setup is depicted in Fig. 3a. Device 1 is mounted on a three-axis optical stage 25, and the light emitted from OLED2 is collected by an infinity-corrected objective lens and refocused onto camera 24 through a tube lens. The optical signal (EL intensity) is finally detected and acquired by camera 24 via an optical microscope 23. A square-wave microwave signal (0.5 Hz) is applied, and the difference in EL between on and off cycles is measured by camera 24. The microwave frequency is swept, and similar images are taken at each frequency. Thus, each pixel of the camera measures the ODMR spectrum associated with one spatial region of OLED2. As a result, a 2DEL image is captured by camera 24 at a small modulation frequency (0.5 Hz), and then the ODMR spectrum of each pixel is achieved through post-processing and analysis of the image, i.e., spatially resolved ODMR. For details, please refer to "Methods". To improve the signal-to-noise ratio (SNR) of the ODMR spectrum for more accurate magnetic field measurement, the pixels of camera 24 are binned to form superpixels (see Fig. 3b). Fig. 3(c) shows the ODMR spectra of two individual superpixels at different locations. The SNR of the data remains relatively low (about 4) even after binning, but the spectra can be well fitted using a double Gaussian function, from which the resonance frequency (f ODMR) is converted into magnetic field strength (|B|) to obtain the magnetic field. Figure 3(d) shows a 2D map of the magnetic field measured over the entire area (152.5 μm × 152.5 μm) with a superpixel size of 0.91 μm (binning size n = 3).

[0038] The superpixel size exceeds the optical diffraction limit of the microscope objective lens (λ / (2NA) = 714 nm) for a typical EL wavelength of λ = 600 nm. The measured magnetic field shows a distinct and smooth gradient change along the x-axis direction, but remains the same along the y-axis direction, which is consistent with the orientation of the test magnet. Furthermore, there is a barely visible ring-like feature in the central part of the magnetic field map, but its edge is blurred and almost invisible. Such ring-like features are related to the overall SNR of the ODMR spectra in various regions and can be seen to cause spatial variations in the uncertainty of the fitting results (see Figure 13). The EL signal and the related ODMR spectra are observed over the entire field of view, which is much larger than the defined size of OLED2 (D = 80 μm) in the photolithography process (see Figure 5(d)). The reason is due to the high hole conductivity of PEDOT:PSS (>1,000 S cm -1 ), and as a result, the holes injected from the ITO electrode 18 diffuse in the in-plane direction within the PEDOT:PSS layer, resulting in EL emission over a much larger area. Figure 3(e) shows enlarged views of a local area (9.1 μm × 9.1 μm) of the 2D map in Figure 3(d) at various binning sizes. It can be seen that as the binning size increases, the spatial resolution of the magnetic field mapping decreases, and accordingly, the standard error of the fit decreases and the measurement sensitivity improves.

[0039] FIG. 11 shows the method of simulation of the preferred embodiment. In FIG. 11(a), a magnetic field simulation of a test magnet using ANSYS Electronics (Maxwell 3D Design with Magnetostatic Solution). The 2D map represents the spatial distribution of the strength of the magnetostatic field generated by the magnet within a region of 14.0 mm × 36.0 mm in the x-y plane having a gap distance of d = 10.0 mm from the upper surface of the magnet. Note that the test magnet is not drawn to scale. The dimensions and material properties of these cylindrical magnets are summarized in Table 1. FIG. 11(b) shows a comparison between the simulated magnetic field and the magnetic field experimentally measured using a Hall probe gaussmeter. Here, the strength of the magnetic field is a function of the moving distance along the z direction from the upper surface of the magnet. Note that the total thickness of the Hall probe 22 is about 1.6 mm, and since the probe was placed immediately adjacent to the magnet, the starting position of the Hall probe measurement is about 0.8 mm (half of the probe thickness) as indicated by the dashed line. The similarity between the magnetic field of the Hall probe and the simulated magnetic field of the simulation is 98.5%. In FIG. 11(c), respectively, as a function of the moving distance along the x direction, and in FIG. 11(d), as a function of the moving distance along the y direction, a comparison between the experimentally measured magnetic field (gray dots) and the simulated magnetic field (colored curves) using various starting positions x0. Note that the x-y coordinates in (c) and (d) are local frames within the 2D map plane and are labeled separately in (a). The similarity between the measured magnetic field and the simulated magnetic field is 99.8% (x0 = 0.2 mm) in (c) and 98.6% (x0 = 0.4 mm) in (d). The similarity calculation formula is shown below.

[0040]

Table 1

[0041] Table 1: Note that the parameters of diameter, length, and material properties are directly obtained from the product data sheet, and the edge radius is estimated based on the inventor's measurements. Here, the edge radius refers to the smooth curvature of the surface edge of the cylindrical magnet. Furthermore, by comparing the simulation with an edge radius of 0.2 mm and the simulation with an edge radius of 0.0 mm, the influence of the edge radius on the simulated magnetic field distribution is investigated. (1) For the far-field region (d > 8.0 mm), the difference in the magnetic field between the two cases is negligibly small in both amplitude and direction. (2) For the near-field region (d < 5.0 mm around the edge region), although the difference is also very small here, it cannot be ignored. Therefore, in the main figure of Figure 2 where the distance d > 10 mm, the simulated magnetic field remains the same regardless of the estimated value of the edge radius.

[0042] · Definition of similarity:

[0043]

Number

[0044] Regarding FIG. 12, this shows the calculation of the standard error of spatially resolved ODMR in a local region of OLED2, which is the standard error of the fit of the resonance peak frequency at various binning sizes in the local region. FIG. 13(a) shows the spatial distribution in the entire field of view of the standard error (SE) of the resonance peak frequency of the ODMR spectrum. This 2D map demonstrates three distinguishable regions. (1) A central region where R < R2 and SE is clearly larger than in the surrounding region. The reason for the large SE in this region is due to the electrical coupling between the resonator and the device electrodes. The inventors speculate that the "wobbling" characteristic noise from the resonator (see FIG. 7) is encoded and enters device 1, where an electrical coupling between ITO electrode 18 and Al electrode 19 is induced. Such electrical coupling is ultimately transmitted to the output (both current and EL) of device 1, reducing the overall SNR. (2) A ring-shaped region where R2 < R < R3 and SE is the smallest. The EL emission in this ring-shaped region is due to the high hole mobility within the PEDOT:PSS layer. Specifically, holes are injected into the PEDOT:PSS layer through a region (R OLED = 40 μm) defined from ITO electrode 18 and then diffuse outward along the in-plane direction within the PEDOT:PSS layer. Under the bias voltage, these diffusing holes are gradually injected into the light-emitting layer along the diffusion path and finally form excitons by combining with electrons injected from the upper Al electrode 19. Since this is a diffusion region, the noise caused by the electrical coupling between the two electrodes 18 and 19 is much weaker compared to the central region. Therefore, the SE in this ring-shaped region is smaller than that in the central region. (3) An edge region where R > R3, where SE is larger compared to the ring-shaped region but is also a diffusion region. The reason is that the EL signal is very weak in this edge region, and thus, the over SNR is very small.

[0045] Figure 13(a) is a 2D map of the standard error of the resonance peak frequency fit with a binning size n = 3 (the entire region contains 166 × 166 superpixels). The OLED region refers to the region where R < R1, and the diffusion region refers to the region where R2 < R < R3. The radius R OLED The yellow dashed circles with a radius indicate the edges of the OLED2 region defined by the photolithography process. Their values are R1 = 30 μm, R2 = 54 μm, R3 = 72 μm, and R OLED = 40 μm. Figure 13(b) shows the spatial distribution of outliers defined as points whose values deviate from the magnetic field range of (754 MHz, 771 MHz). The actual values of the resonance peak frequency and the standard error of those outliers are interpolated by adjacent points, and the distance is indicated by the k value. The selection of these radius values is to cover as many points as possible in each region while avoiding outliers. These outliers are caused by defects during the photolithography process and degradation of device 1 during measurement.

[0046] Figure 14 shows the standard error (SE) of the double Gaussian fit of the spatially resolved ODMR spectra for different binning sizes. The relationship between the magnetic field sensitivity and the spatial resolution of the magnetic field mapping is quantitatively investigated. Generally, the magnetic field sensitivity is defined as the minimum detectable magnetic field B min which corresponds to the error of individual measurements. By combining signals from adjacent pixels, the measurement error can be

[0047]

Number

[0048]

Number

[0049] Therefore, for the magnetic field mapping with a spatial resolution of ~0.91(5) μm in Fig. 3(d) (corresponding to a binning size of n = 3), the magnetic field sensitivity is approximately 233.04 μTHz in the OLED region -1 / 2 and approximately 163.16 μTHz in the diffusion region -1 / 2 respectively. When the superpixel size is increased to approximately 14.64 μm (binning size n = 48), the sensitivity is approximately 136.88 μTHz in the OLED region -1 / 2 up to approximately 40.75 μTHz in the diffusion region -1 / 2 respectively. As described above, the measured sensitivity follows the general 1 / n rule, but the actual sensitivity improvement rate (e.g., in the diffusion region

[0050] [Number] ) is very small compared to the trade-off ratio of the spatial resolution of 48÷3 = 16 times. This is presumably because the improvement in SNR due to the binning process is partially suppressed by device-related noise including the variation in EL intensity caused by the electrical coupling between OLED2 and resonator 3 (see Fig. 8) and other technical contributions.

[0051] Regarding 1 / n, refer to FIG. 15 regarding the sensitivity calculation of spatially resolved ODMR. Here, the magnetic field sensitivity of spatially resolved ODMR as a function of the superpixel size in both the OLED and the diffusion region. See further details regarding the region definition in FIG. 13. The dataset in FIG. 15 can be fitted using the function y = a / x + b. The fitted parameters are: (1) in the OLED region, a = 98.81 (±2.12), b = 132.33 (±0.76); (2) in the diffusion region, a = 127.55 (±2.44), b = 33.77 (±0.87). The units of the parameters a and b are μT·Hz -1 / 2 and μT·Hz -1 / 2 respectively.

[0052] The magnetic field gradient sensitivity of device 1 is calculated from the uncertainty of the magnetic field gradient given by G = ΔB / Δx, where ΔB = B(x2) - B(x1) is the measured magnetic field difference between two superpixels located at x1 and x2, and Δx = x2 - x1 is the distance between them (see the inset in FIG. 4). Based on error propagation, the minimum detectable gradient δG is given as follows.

[0053]

Equation

[0054] Since ΔB = B(x2) - B(x1), (δΔB) 2 =[δB(x2)] 2 +[δB(x2)] 2 where δB(x i (i = 1, 2) is the uncertainty of the magnetic field (or the minimum detectable magnetic field). Here, assuming that the uncertainty of the magnetic field is independent of position and ideally the same throughout the device, i.e., δB(x2) = δB(x1) = δB, the following results are obtained.

[0055]

Equation

[0056] Similarly, the following results are obtained.

[0057]

Number

[0058] Since the entire measurement system is firmly fixed on the optical table and no relative movement between the camera 24 and the device 1 has been observed so far, the actual uncertainty of distance measurement caused by vibration and relative displacement is considered to be negligibly small compared to w.

[0059] Substituting equations (2 - 4) into equation (1) and using G = ΔB / Δx, the following can be obtained.

[0060]

Number

[0061] Equation (5) can be rewritten as follows.

[0062]

Number

[0063] In the above equation (6 - 1), δB is the minimum detectable magnetic field (i.e., the uncertainty of the magnetic field as described above), and as shown in Figure 14, it depends on the superpixel size w (i.e., the binning size n). δx = w is the uncertainty of distance measurement as shown in equation (4). Equation (6 - 1) can also be rewritten as equation (6 - 2) to show all the independent variables w, Δx, and ΔB.

[0064] According to Equation (6-2), δG is a monotonically increasing function of the variable ΔB, where w and Δx are fixed values. Therefore, the minimum detectable gradient δG can be further reduced by selecting the minimum magnetic field difference shown in Equation (2).

[0065]

Number

[0066]

Number

[0067]

Number

[0068] Finally, the magnetic field gradient sensitivity η G is given as follows.

[0069]

Number

[0070] In Equation (8), all uncertainties (i.e., errors) must be relatively small in order to justify the above error propagation analysis.

[0071] Device 1 can also be used to measure the magnetic field gradient on the μm scale in parallel with magnetic mapping. The magnetic field gradient is defined as G = ΔB / Δx, where ΔB is the measured magnetic field difference between two superpixels of size w × w acting as two virtual point sensors, and Δx is the center-to-center distance between them. The average gradient along the x-axis in Figure 3(d) is

[0072]

Number

[0073] For details of the calculation, see Fig. 15. As shown in Fig. 4, the magnetic field gradient can be achieved with a relatively low gradient sensitivity on the μm scale. In general, the gradient sensitivity can be improved by increasing the virtual pixel size or the gap distance, or both, at the expense of the spatial resolution. It is understood that all the noises that limit the magnetic field sensitivity, as described above, also limit the gradient sensitivity.

[0074] One important issue in using any resonance-based technique for magnetic field sensing is the measurement time to find the resonance frequency over a wide range. In particular, it can be time-consuming when the frequency step size is small and the averaging time is long for a better SNR. Operationally, it is expected that the measurement time can be shortened by using a wide-range coarse scan followed by a fine scan over the resonance range. However, such an improvement is related to the frequency step s It may be limited by the resonance linewidth that sets the upper limit of Iz. Another issue is the magnetic field sensitivity in both EDMR and ODMR, especially in spatially resolved ODMR. This can be improved in several ways. First, by minimizing sample-related noise, particularly the electrical coupling between the resonator and the OLED, through device architecture optimization. Second, the sensitivity can be further enhanced by adopting coherent modulation techniques (e.g., Ramsey method or dynamic decoupling method). One of the motivating factors for this research was the existence of a reasonably long spin-phase coherence time of polarons in organic devices at room temperature. T2 approaching 1 μs at room temperature has been observed in EDMR measurements, and the use of deuterated organic materials can be used to increase these times. A collaborative effort aimed at identifying or developing materials with even longer phase coherence times seems promising.

[0075] In NV-based detection, multiple resonance peaks can occur due to multiple different crystal axes of NVs in the diamond. In contrast, the inventors' device sensor, which is sensitive to the strength of the external magnetic field regardless of the magnetic field orientation, has only one resonance peak. This means that sensor alignment is not required in detecting the magnetic field strength. This property of not requiring alignment may be useful in applications where the magnitude rather than the orientation of the magnetic field is important, and can reduce the inaccuracies caused by improper orientation of the magnetometer (i.e., Hall effect probe). It should be noted that the amplitude of the resonance signal is proportional to the projection of the microwave field B1 along the static external magnetic field B0 and reaches a minimum or disappears when B0 is parallel to B1. The sensitivity problem caused by this can potentially be solved by generating a B1 field with a large directional non-uniformity across the OLED such that a measurable resonance is produced regardless of the orientation of B0, as there is always a component of the B1 magnetic field projected orthogonally to B0.

[0076] To detect the direction of the magnetic field, it is possible to expand the device architecture by using two mutually perpendicular metal strip lines integrated below the OLED. This provides an in-plane microwave field with an arbitrary direction. Together with the out-of-plane microwave field from the already integrated resonator, there will be three independent microwave fields perpendicular to each other. By repeating the measurements in each microwave field, the corresponding vector components of the unknown magnetic field can be detected. It should be noted that the use of metal strip lines can block light emission and, as a result, limit the optical readout in ODMR. Furthermore, these metal layers, including the top Al electrode of the device, can distort the external magnetic field, especially at high magnetic fields, increasing the challenges for accurate vector measurements.

[0077] Advantageously, Device 1 provides an OLED-based integrated quantum magnetometer capable of both optical and electrical readouts. Device 1 can function not only as a point sensor under electrical operation by bulk EDMR or ODMR, but also as a virtual array of sensors under optical readout by spatially resolved ODMR. Optical access enables magnetic field mapping, and a magnetic field sensitivity of 163.2 μTHz -1 / 2 is achieved in Device 1 with a spatial resolution of 0.91 μm. This conceptually demonstrates electrically driven, OLED-assisted driven magnetic sensing and mapping using Device 1 on-chip; the magnetic field sensitivity can be further improved by several methods, including minimizing device-related noise by optimizing the device architecture; improving the SNR of spatially resolved ODMR by utilizing spin coherent operation; and reducing the resonance linewidth by using deuterated materials. Device 1 provides a chip-scale, laser-free OLED-based platform for magnetic field sensing and mapping, with potential for ubiquitous quantum sensing and quantum mapping applications, driving significant investment in consumer OLED technology.

[0078] Now, turning to the fabrication of the integrated microwave resonator 3, in order to enable optical access to device 1, the structure of resonator 3 and OLED 2 should be laterally separated so that light can be emitted out from the ITO / glass side of substrate 4. The main challenge in integrating resonator 3 and OLED 2 on the same glass substrate 4 based on ITO was how to electrically insulate them from each other. Here, the inventors adopted the atomic-layer-deposition (ALD) method at low temperature for the deposition of the insulating layer to provide a conformal and high-quality thin electrical insulating layer with a thickness of . The main procedure is as follows. 1) A glass substrate (20.0 mm × 30.0 mm × 0.7 mm) with pre-patterned ITO (120 nm) was purchased from a company for commercial purposes. 2) A first insulating layer Al2O3 was prepared between the ITO layer and the next resonator layer. The geometry of the insulating layer was patterned by a standard photolithography process (MA6 system with negative photoresist nLOF2020 and developer ZA826MIF), and an Al2O3 (45 nm) layer was deposited by low-temperature ALD, followed by a lift-off process in an NMP bath. 3) A resonator layer was prepared on top of the first insulating layer. The structure of the resonator was defined by standard photolithography (the same as in step 2), and then a metal layer of Ti (10 nm) / Au (500 nm) / Ti (10 nm) was thermally deposited in a thermal deposition chamber (Jurt J. Lesker), followed by a standard lift-off process. The 10-nm Ti layer was an adhesion layer. 4) A second insulating layer was prepared on the resonator in the same way as the first insulating layer in step 2. This second insulating Al2O3 (45 nm) layer is for electrically insulating resonator 3 itself from the upper electrode of the deposited OLED 2 in the subsequent device 1 fabrication process. The final layer structure of the resonator integration template is ITO lower electrode layer (120 nm) / first insulating layer of Al2O3 (45 nm) / Ti microwave resonator layer (10 nm) / Au (500 nm) / Ti (10 nm) / second insulating layer of Al2O3 (45 nm).

[0079] In particular, referring to FIG. 5, a micrometer-sized OLED 2 having a microwave resonator 3 is integrated on the same substrate 4. Such an integrated device should have good capabilities for both EDMR measurement and ODMR measurement at room temperature, good electrical insulation between the resonator 3 and the OLED 2, and an open ITO surface for mounting the micrometer-sized OLED 2 thereon. In order to extract light from the lower ITO electrode 18 side of the device 1, it is necessary to laterally separate the layer of the resonator 3 from the ITO electrode 18. Gold (Au) is an excellent room-temperature conductor, resistant to most acids / chemicals, and is preferred for the layer of the resonator 3. An important procedure for integrating the resonator 3 with the OLED 2 on the same glass substrate 4 based on ITO is how to electrically insulate the layer of the resonator 3 from the two electrode layers 18 and 19 of the OLED 2, which are the lower ITO electrode 18 as the anode and the upper Al electrode 19 as the cathode. Here, the low-temperature atomic layer deposition (ALD) method is adopted for the deposition of the insulating layer. Different from thermal evaporation and electron beam evaporation where the stepped edges are not fully covered, the ALD method is conformal and provides a very high-quality insulating layer even with a thin layer thickness, which is essential for electrically insulating some regions with sharp edges.

[0080] In particular, referring to FIG. 5, FIG. 5(a) shows the patterned ITO electrode 18 on the glass substrate 4. The diameter of the circular end of the electrode is about 120 μm. FIG. 5(b) shows the first insulating layer on the ITO electrode 18, and FIG. 5(c) shows the microwave omega-shaped resonator 3. The end of the ITO electrode 18 is located at the center of the center of the omega shape, and the intersection of the resonator 3 and the ITO is electrically insulated by the first insulating layer. FIG. 5(d) shows the second insulating layer on the resonator 3. There is an opening at the center of the insulating layer that defines the geometric shape of the active region of the OLED 2. FIG. 5(e) is a photograph of the resonator integration template. The right side of the resonator 3 shows a region covered by the second insulating layer presenting a relatively yellowish color, and FIG. 5(f) is an enlarged view of the template, showing the patterned transparent OLED 2 region at the center of the resonator. The diameter of the patterned area is about 80 μm. The inner diameter of the resonator is about 200 μm. Note that the overall layer structure is glass (0.7 mm) / ITO (120 nm) / Al2O3 (45 nm) / Ti (10 nm) / Au (500 nm) / Ti (10 nm) / Al2O3 (45 nm).

[0081] The pre-patterned ITO / glass substrate 4 is purchased from Kintec Company (Hong Kong). The ITO substrate is cleaned by standard cleaning procedures and dried overnight at 120 °C in a vacuum drying oven before use. Note that the dimensions of the glass substrate are 30.0 (±0.05) mm × 20.0 (±0.05) mm × 0.7 (±0.01) mm. The shadow mask used for the thermal deposition of the upper Al electrode 19 of the OLED2 is accurately cut by a laser based on the substrate dimensions. The accuracy of the shadow mask dimensions is particularly important for good alignment between the substrate and the shadow mask, and this alignment is an important step in the subsequent OLED2 manufacturing process (see Figure 6).

[0082] The photoresist structures for the two insulating layers and the layers of the microwave resonator 3 are prepared by a standard photolithography process using the MA6 system with the negative photoresist nLOF2020 and the developer ZA826MIF with optimized parameters. The details of the photolithography process are as follows. 1) Spin nLOF2020 on the substrate at 3000 RPM for 30 seconds to make the thickness of the photoresist layer about 2.3 μm. 2) Pre-bake the photoresist at 115 °C for 1 minute. 3) Expose to UV for 4.5 seconds. 4) After exposure, bake (PEB) the photoresist at 115 °C for 1 minute. 5) Develop in AZ826MIF for 1 minute. 6) Rinse with deionized water for 20 seconds and dry with a nitrogen gun. 7) Bake further at 115 °C for 2 minutes to remove residual water. 8) Perform post-plasma cleaning for 10 minutes (plasma etching rate is approximately 30 nm / min).

[0083] The reason for selecting Al2O3 as the insulating material is its excellent electrical insulation properties, and more importantly, its compatibility with the materials and manufacturing methods used in the preferred embodiments. The breakdown electric field of Al2O3 by ALD at room temperature is approximately 8 MV / cm (or 0.8 V / nm). Therefore, a thickness of 45 nm is sufficient for an OLED with an operating voltage range of 0 V to 15 V. The ALD system is the CNT Savannah S200. The precursors of Al2O3 in ALD are water vapor (H2O) and trimethylaluminum (TMA). The chamber temperature of the ALD process was set at 120 °C. If the chamber temperature is too high, the photoresist will solidify, making the subsequent lift-off process very difficult, so it cannot be set too high. In principle, the temperature can be lowered, such as 80 °C, which facilitates the next lift-off process, but the cycle time increases, and the total deposition time increases dramatically. There is a trade-off between the deposition temperature and the deposition time cost. The total deposition time of 45 nm of Al2O3 by ALD at 120 °C is approximately 9.5 hours.

[0084] Following ALD, a lift-off procedure for Al2O3 was performed by immersing the sample in an N-methyl-2-pyrrolidone (NMP) bath. In order for the NMP to penetrate the conformal insulating layer more quickly and attack the underlying photoresist, it was necessary to lightly scratch the surface of the sample by hand in areas without pattern features. For the lower insulating layer, the surface near the edge of the substrate could be scratched relatively easily because there was no pattern underneath. For the upper insulating layer, a cascade probe station and a sharp metal probe tip were used to gently cut the photoresist pillars inside the resonator downward from the top. After scratching, the sample was immersed in the NMP bath on a hot plate at 100 °C in the lift-off chamber until the lift-off procedure was completed. The sample was immersed in the NMP bath on a hot plate at 100 °C in the lift-off chamber until the lift-off procedure was completed.

[0085] For the layer deposition of resonator 3, a substrate with a pre-patterned photoresist structure was transferred to a thermal evaporation chamber (Jurt J. Lesker) for metal deposition. The vacuum condition was about 10 -6 mbar, and the layer stack was Ti(10 nm) / Au(500 nm) / Ti(10 nm). The first 10-nm Ti layer was deposited as an adhesion layer for depositing Au on the glass surface next. For the deposition of the Au layer, to minimize heating effects such as deformation or softening on the pre-patterned photoresist structure, the first 100 nm was deposited at a low speed of 0.5 Å / s. The next 400 nm was deposited at a high speed of 2 Å / s for time saving. The second 10-nm Ti layer was deposited as another adhesion layer for spin-coating photoresist in the next photolithography procedure. Subsequently, standard lift-off was performed in a 100 °C NMP bath.

[0086] Figure 6(a) shows a schematic of the fabrication of device 1 where micrometer-sized OLED2 is fabricated within the active region (D ≈ 80 μm), and in Figure 6(b) the top Al electrode 19 is deposited by using a well-aligned shadow mask. Figure 6(c) is a photograph of the PCB platform for mounting and electrical connection of device 1. Device 1 is mounted on the PCB via a 3D-printed plastic lid. Device 1 is electrically connected to the PCB via pogo pins (resonator 3 is AC-connected, OLED2 is DC-connected). OLED2 is encapsulated by using a square glass coverslip (10 mm × 10 mm) with a cavity (depth 300 μm) inside to avoid physical contact with the top Al electrode 19. Figure 6(d) is a photograph of device 1 during operation. The outlines of the bottom ITO electrode 18, the top Al electrode 19, and the Au resonator 3 are emphasized by dashed lines. There is a small offset from the center in the top Al electrode 19, which is due to the manual alignment of the shadow mask during the OLED2 fabrication procedure. The scale bar in (d) is 100 μm.

[0087] In the method of integrating micrometer-sized OLED2 on a resonator template, the resonator integration template was first cleaned for 10 minutes using a UV ozone cleaner (purchased from Osilla), followed by spin-coating PEDOT:PSS (purchased from Heraeus, Al 4083) at 3000 rpm for 1 minute and baking on a hot plate at 120 °C for 2 hours to obtain a film thickness of about 35 nm. Then, the sample was transferred to a glove box (O2 < 0.5 ppm, H2O < 0.5 ppm), where SY-PPV solution (3 mg / ml in toluene) was spin-coated at 1200 rpm for 1 minute and then baked on a hot plate at 60 °C for 2 hours to obtain a film thickness of about 80 nm. Before spin-coating, the SY-PPV solution was filtered using a PTFE syringe filter with a pore size of 0.45 μm to remove polymer aggregates. The extra portion of the SY-PPV layer on the Au resonator 3 and the electrode pads was carefully removed using a cotton swab. Next, the sample was transferred to a high-vacuum chamber (<10 -8 mbar) to deposit LiF (1 nm) / AI (100 nm) using a shadow mask. To avoid any possibility of short-circuit connection between the resonator 3 and the upper Al electrode 19, the shadow mask was carefully aligned with the substrate so that Al was deposited only on the target area (the upper part of the second insulating layer area). After manufacturing, the device 1 was encapsulated with a thin glass lid having a recessed cavity using a UV-activated epoxy inside the glove box. To prevent deterioration of the device in air, a thin desiccant sheet (as a moisture and oxygen absorber) was attached to the inner surface of the recessed cavity.

[0088] Referring to the EDMR measurements of FIGS. 1 and 2, OLED2 was operated at a constant current of 0.5 μA (Keysight, SMU B2901A) at room temperature. The device 1 was mounted on a PCB via a 3D-printed lid base board, the device 1 was electrically connected to the PCB via the pogo pins integrated on the PCB, and the PCB was connected to an SMA cable 16 via It was used to connect to all the measuring instruments. The signal generator 13 (SRS SG396) was connected to the microwave resonator 3 via the electrodes 11 and 12, and an input microwave signal pulse - modulated with a 10 μs pulse width and 10 kHz modulation was provided. The other end of the resonator 3 was connected to a 50 Ω terminator. The periodic change in the device current during the EDMR measurement was first amplified through a low - noise current amplifier (SRS SR570) using a 6 dB band - pass filter at 10 kHz, and then detected by a lock - in amplifier (SRS SR865A).

[0089] Regarding the spatial resolution of the ODMR measurement, referring to Fig. 3(a), the device 1 is mounted on the three - axis optical stage 25 and then aligned with the optical imaging system 23 / 24. The light emitted from the ITO side of the device 1 is collected by an infinity - corrected objective lens (Mitutoyo Plan - Apochromat Objective, NA = 0.42, working distance = 20.0 mm, focal length = 10.00 mm), and then refocused onto a scientific CMOS camera (Andor iStar sCMOS 18U - A3 with an operating temperature of 0.0 °C) through a matching tube lens (focal length = 200.0 mm). Here, the EL intensity signal was detected and acquired by the camera 24. At a magnification of 20 times, the pitch between two adjacent pixels on the OLED2 plane is approximately 0.30(5) μm. The OLED2 was operated at a constant current of 0.5 μA (Keysight, SMU B2901A) at room temperature, and the resonator was connected to the signal generator 13 (SRS SG396). Mitutoyo Plan - Apochromat Objective, NA = 0.42, working distance = 20.0 mm, focal length = 10.00 mm), and then refocused onto a scientific CMOS camera (Andor iStar sCMOS 18U - A3 with an operating temperature of 0.0 °C) through a matching tube lens (focal length = 200.0 mm). Here, the EL intensity signal was detected and acquired by the camera 24. At a magnification of 20 times, the pitch between two adjacent pixels on the OLED2 plane is approximately 0.30(5) μm. The OLED2 was operated at a constant current of 0.5 μA (Keysight, SMU B2901A) at room temperature, and the resonator was connected to the signal generator 13 (SRS SG396).

[0090] A test magnet 20 was placed next to device 1 to provide a static external magnetic field for Zeeman energy splitting. The microwave field output was modulated in 200 operating sequences by a 0.5 Hz square wave sequence, and the on-off cycle EL intensity signal was recorded by camera 24 (exposure time of 980 ms) at each microwave frequency. The microwave frequency was swept, and finally, a full set of EL intensity data was recorded as a function of the microwave frequency. By calculating the average change in the EL signal between on-off cycles as a function of the microwave frequency, the ODMR spectrum at each camera pixel, i.e., the spatially resolved 2D ODMR spectrum, could be obtained.

[0091] As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

[0092] As used herein, the term "comprising" (and its grammatical variations) is used in an inclusive sense of "including" or "having", and is not used in the exclusive sense of "consisting only of". from".

Claims

1. A substrate having an electrically inert and optically transparent top and bottom surface, A microwave or RF generator element disposed on the upper side of the substrate, configured to be connected to an electrode for connecting to the microwave or RF generator, A heterostructured organic light-emitting diode (OLED) disposed adjacent to the microwave or RF generator element, configured to be connected to a first electrode and a second electrode, A magnetic field sensor equipped with the following features.

2. The sensor according to claim 1, wherein the microwave or RF generator element is a split-ring resonator having an arc-opening length, and each end of the split ring is configured to be connected to the microwave or RF generator, and the OLED is centrally located within the split-ring resonator.

3. The sensor according to claim 1 or 2, wherein the substrate is formed from glass or from a rigid or flexible plastic material.

4. The sensor according to claim 1 or 2, wherein the OLED includes a first electrode or a second electrode disposed on the upper side of the substrate, the second electrode or the first electrode is disposed above the first electrode, and a dielectric layer is disposed between them.

5. The sensor according to claim 4, wherein the second electrode is connected to a digital acquisition device.

6. The sensor according to claim 2, wherein the arc length of the microwave or RF generator element of the split-ring resonator is defined by a string having a predetermined length and each string end being configured to be connected to the electrode for connection to the microwave or RF generator.

7. The first OLED electrode ITO or the second OLED electrode ITO is a digital acquisition device The sensor according to claim 4, wherein the second OLED electrode or the first OLED electrode is connected to a signal multiplexing unit.

8. The sensor according to claim 1, comprising a permanent magnet adapted to provide a static magnetic field.

9. The sensor according to claim 1, wherein the OLED is configured to be read optically through the substrate.

10. The sensor according to claim 9, wherein the OLED is optically read by a camera.

11. The sensor according to claim 10, wherein the camera is a digital camera having a camera sensing element based on CMOS.

12. The sensor according to claim 10 or 11, comprising a microscope objective lens disposed between the camera and the OLED.

13. The sensor according to claim 1, wherein the OLED is disposed within the AC magnetic field B1 of the microwave generator element field.

14. The sensor according to claim 1, wherein the OLEDs are configured to be imaged by an imaging device in order to provide a virtual array of OLEDs therefrom.

15. One or more spaced substrates having an upper and lower surface, which are electrically inert and optically transparent, A plurality of spaced microwave or RF generator elements arranged on a single substrate, or one or more microwave or RF generator elements arranged on the upper side of each substrate, each configured to be connected to an electrode for connection to a microwave or RF generator, A heterostructure organic light-emitting diode (OLED) is disposed adjacent to each microwave or RF generator element, and each heterostructure organic light-emitting diode (OLED) is configured to be connected to a first electrode and a second electrode, A magnetic field sensor equipped with the following features.

16. An electrically inert and optically transparent substrate having an upper and lower surface, and a microwave or RF generator element disposed on the upper side of the substrate, configured to be connected to an electrode for connection to the microwave or RF generator, A plurality of heterostructure organic light-emitting diodes (OLEDs) arranged adjacent to the microwave or RF generator element, each configured to be connected to a first electrode and a second electrode, A magnetic field sensor equipped with the following features.

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