A non-destructive imaging system and imaging method for spin and valley polarization signals

Abstract

The present invention discloses a lossless imaging system for spin and valley polarization signals, including an XY scanning stage, a laser, a photodetector, a plurality of lock-in amplifiers and a CCD camera. By setting a micron-level high-precision XY scanning stage, a selected area can be locally scanned to achieve spatially resolved imaging of the device. The present invention receives photocurrent or voltage signals through a lock-in amplifier, and has more accurate acquisition results for weak signals. The present invention integrates excitation light of different wavelengths, and can switch the laser wavelength at any time to meet the required excitation light wavelength of different samples, and can expand the integration of more wavelengths of excitation light at any time. The present invention applies the lossless imaging system to the measurement of tin sulfide crystals, discovers the channel edge spin accumulation phenomenon of tin sulfide crystals, and explores its relationship with the source-drain bias current of the device.

Description

Technical Field

[0001] The invention belongs to the field of nano science and technology, and in particular relates to a lossless imaging system of spin and valley polarization signals. Background Art

[0002] Spin electronics and valley polarization of low-dimensional materials are important research directions in the field of nanoscience. Developing new spin devices by manipulating the intrinsic properties of electron spin will help reduce the power consumption and cost of existing devices and improve the information storage and transmission capabilities of existing devices, and has huge application potential.

[0003] In current device measurements, people mainly use electrically injected and optically injected spin currents. However, due to the limitations of the test environment and equipment configuration, data collection and imaging are limited to the transport behavior of a single device or a certain location in the channel material, and high-precision spatially resolved imaging of the device cannot be achieved.

[0004] Currently, the main method for collecting device spin signals is micro-area point measurement or line scanning, which cannot provide regional surface imaging and is cumbersome to operate. Summary of the invention

[0005] In view of the above-mentioned defects, the present invention provides a non-destructive imaging system for spin and valley polarization signals, which realizes surface imaging by controlling the in-plane movement of the piezoelectric displacement stage, and detects weak signals using a phase-locked amplifier, so that the obtained measurement results are accurate.

[0006] A non-destructive imaging system for spin and valley polarization signals, comprising a laser, an excitation optical path, a reflection optical path, a translation stage, a microscopic imaging system, i.e., an internal optical path of a microscope and a CCD camera, and a measurement system, i.e., a phase-locked amplifier and a source meter;

[0007] The sample holder is provided on the translation stage for fixing the sample. The sample is placed on the sample holder and connected to the sample holder through a gold wire. The sample holder is connected to the first lock-in amplifier, the second lock-in amplifier and the source meter through pins, which are used to display tiny electrical signals, sample reflectivity signals and apply bias electrical signals respectively.

[0008] The laser is connected to the first phase-locked amplifier and the second phase-locked amplifier, and a reference frequency is input to the two phase-locked amplifiers; the laser emits a linearly polarized laser into an excitation light path, the laser of the excitation light path irradiates the sample, the sample reflects the laser, a part of the reflected laser is directly fed back to the CCD camera for display imaging, and the other part of the reflected laser enters the reflection light path in the optical path box at the top of the microscope, and is fed back to the photodetector through a beam splitter and a reflector in the reflection light path; the photodetector is connected to the second phase-locked amplifier to obtain a sample reflection signal to determine the scanning position.

[0009] Preferably, the laser includes several sub-lasers and their controllers integrated in a main laser box, an external expansion laser and its controller; the linearly polarized lasers emitted by the main laser box and the external expansion laser can enter the same excitation optical path.

[0010] Preferably, the laser emitted from the main laser box directly enters the excitation optical path through a rotatable first reflector, wherein a chopper is further provided between the extended laser and the excitation optical path, the chopper being connected to the first phase-locked amplifier to control the reference frequency input to the first phase-locked amplifier; a plurality of sub-lasers in the main laser box output lasers of different wavelengths through their correspondingly connected controllers, which are guided out from the light outlet of the laser box after adjustment by the reflector and the beam splitter, and enter the excitation optical path through the rotatable first reflector located downstream of the light outlet optical path.

[0011] Preferably, the excitation light path changes the propagation direction of the laser through a reflector. Specifically, after being emitted from the laser, the linearly polarized laser passes through the reflectors in sequence and enters the optical path box on the top of the microscope, wherein a first aperture and a second aperture are provided in the middle of the optical path between the laser and the reflector for collimating the laser.

[0012] Preferably, the optical path box on the top of the microscope includes a fourth reflector and a fifth reflector for changing the direction of the laser. At the same time, a quarter glass slide is coupled to the optical path between the fourth and fifth reflectors to change the polarization direction of the laser so that the laser can be changed from linear polarization to elliptical polarization and circular polarization. The light reflected by the fifth reflector passes through the first beam splitter and the second beam splitter and enters the internal optical path of the microscope.

[0013] Preferably, the reflected light path is the part of the laser reflected from the sample stage that enters the photodetector through the internal light path of the microscope and the second beam splitter and then the light path box on the top of the microscope. Specifically, the reflected laser enters the light path box on the top of the microscope through the second beam splitter, is split by the first beam splitter in the box, and is reflected by the sixth reflector into the photodetector.

[0014] Preferably, the translation stage includes a stacked main scanning translation stage and a secondary scanning translation stage, which respectively perform coarse and fine adjustments on the sample position, and the main scanning translation stage is placed below the secondary scanning translation stage; the main scanning translation stage controls the x, y, and z directions through three motors and is connected to a joystick to perform coarse adjustments and focusing on the sample position; the secondary scanning translation stage is connected to a computer through a controller, and the sample position can be finely adjusted in the xy plane in the software, and the micron-level scanning step length in the plane can be set.

[0015] The present invention also discloses an imaging method of a lossless imaging system of spin and valley polarization signals, comprising the following steps:

[0016] Step 1: Prepare a sample, place the sample on the sample holder with gold wire and silver glue and connect it to the sample holder pin, move the main scanning stage and the secondary scanning stage, find the position of the sample under the microscope, and focus the excitation light on the sample surface; control the secondary scanning stage to move the sample in the field of view at the micrometer level based on software, move the sample to the center of the field of view for point measurement, or perform surface scanning measurement and imaging of the sample by setting the scanning step length and the scanning time of each point;

[0017] Step 2, by applying different source-drain bias voltages to the sample, changing the rotation angle of a quarter of the glass slide, using the obtained left circularly polarized light and right circularly polarized light to perform surface scanning on the same position of the sample, and subtracting the two scanned images to obtain the spin current signal diagram of the sample.

[0018] Preferably, the sample is a material with a spin-split energy band structure, which generates a photoelectric signal related to the polarization of light. When a bias current is applied to both ends of the sample, when circularly polarized light is irradiated onto a device made of the sample, the electron spins generated by the left circularly polarized light and the right circularly polarized light are in opposite directions, and the current-induced out-of-plane spins accumulate near both ends of the opposite channel edges of the device, changing the rotation angle of a quarter of the glass slide, and using the obtained left circularly polarized light and right circularly polarized light to scan the same position of the sample, the result of subtracting the obtained scanned images is the spin current signal of the sample.

[0019] Preferably, the sample is tin sulfide crystals, which are grown on a magnesium oxide substrate by physical vapor deposition. By applying different source-drain bias voltages to the tin sulfide crystals, the spin signal image and reflectivity signal of the tin sulfide are measured, and a spin current signal diagram of the tin sulfide crystals is obtained.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention can realize surface imaging by controlling the piezoelectric displacement stage to move in a plane, thereby solving the problem that the device spin signal is collected in the prior art by micro-area point measurement or line scanning, which cannot provide regional surface imaging and is cumbersome to operate. At the same time, the weak signal is detected by combining a phase-locked amplifier, thereby obtaining accurate measurement results.

[0022] (2) The present invention uses a phase-locked amplifier whose reference frequency comes from a laser, and can accurately identify weak electrical signals at the microvolt and nanovolt levels obtained in device measurement, thereby capturing spin signals under helical light excitation;

[0023] (3) The present invention controls the movement of the sample stage through the main stage and the secondary stage. The main stage controlled by the remote control handle allows the user to easily find the position of the sample under the microscope and focus the excitation light on the sample surface. The software-controlled secondary stage allows the user to move the sample at the micrometer level, accurately set the required scanning range and micrometer scanning step length, and perform coarse scanning and fine scanning as required;

[0024] (4) The laser box of the present invention integrates excitation lights of different wavelengths, and the laser wavelength can be switched at any time to meet the required excitation light wavelength of different samples, and more wavelengths of excitation light can be expanded and integrated at any time;

[0025] (5) The present invention uses physical vapor deposition to produce tin sulfide crystals and fabricate Hall bar shaped tin sulfide devices. Further measurements reveal that there are spin accumulation signals at the channel edge, and the direction and magnitude of the signals vary with the direction and magnitude of the applied source-drain bias voltage, demonstrating the feasibility and convenience of the spin signal imaging method and providing a new type of material for the fabrication of spin devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below.

[0027] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of a laser according to an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of an excitation light path according to an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of a reflected light path according to an embodiment of the present invention;

[0031] Figure 5 Schematic diagram of a top optical path box of a microscope according to an embodiment of the present invention;

[0032] Figure 6 is a schematic diagram of a device according to an embodiment of the present invention;

[0033] Figures 7 to 9 The figure is a spin signal image and a reflectivity signal diagram of tin sulfide measured by applying different source-drain bias voltages according to an embodiment of the present invention.

[0034] Reference numerals:

[0035] 1-laser, 2-excitation light path, 3-first beam splitter, 4-second phase-locked amplifier, 5-photodetector, 6-CCD camera, 7-second beam splitter, 8-third beam splitter, 9-internal light path of microscope, 10-objective lens, 11-source meter, 12-first phase-locked amplifier, 13-main scanning stage, 14-second scanning stage, 15-sample holder, 16-computer, 17-white light source, 18-main laser box, 19-expansion laser, 20-chopper, 21-second reflector, 22-rotatable first reflector, 23-first aperture, 24-second aperture, 25-third reflector, 26-fourth reflector, 27-quarter slide, 28-fifth reflector, 29-sixth reflector. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The present invention can perform local scanning of the selected area by setting a micron-level high-precision XY scanning stage to achieve spatial resolution imaging of the device. The present invention receives photocurrent or voltage signals through a phase-locked amplifier, and has more accurate acquisition results for weak signals. The present invention integrates excitation light of different wavelengths, and can switch the laser wavelength at any time to meet the required excitation light wavelength of different samples, and can expand the integration of excitation light of more wavelengths at any time.

[0038] Specifically, Figures 1 to 5 As shown, a non-destructive imaging system of spin and valley polarization signals includes a laser, an excitation optical path, a reflection optical path, a translation stage, and a translation stage control module;

[0039] The displacement table is provided with a sample stage for fixing the sample, and the first phase-locked amplifier 12 and the source meter 11 are connected in parallel at both ends of the displacement table. The sample in the sample holder 15 on the sample table is connected to the first phase-locked amplifier 12 through a wire to collect the electrical signal of the sample. The laser 1 is connected to the first phase-locked amplifier 12 and the second phase-locked amplifier 4. With a given reference frequency, the laser 1 emits a linearly polarized laser into the excitation light path. The laser of the excitation light path is irradiated to the sample stage through the first beam splitter 3. The sample stage reflects the laser, and a part of the reflected laser is directly fed back to the CCD camera 6, and the other part of the reflected laser enters the reflection light path in the optical path box at the top of the microscope through the second beam splitter 7. In the reflection light path, it passes through the first beam splitter 3 and the sixth reflector 29 and is fed back to the photodetector 5; the photodetector 5 is connected to the second phase-locked amplifier 4 to obtain the sample reflectivity signal for determining the scanning position.

[0040] like Figure 2 As shown, the laser 1 integrates five commonly used lasers from 400nm to 900nm, which are coupled into the optical path in two ways. The laser 1 includes a main laser box 18, an extended laser 19, a chopper and a controller, wherein the main laser box 18 includes 4 sub-lasers, 4 controllers connected to the sub-lasers, 8 reflectors and 4 beam splitters; the extended laser 19 is arranged outside the laser box, and the lasers emitted by the main laser box 18 and the extended laser 19 are 5 selectable linearly polarized lasers, which enter the excitation optical path.

[0041] The laser emitted by the main laser box 18 directly enters the excitation optical path through the rotatable second reflector 21. A chopper 20 is also provided between the optical path of the expansion laser 19 and the second reflector 21. The chopper 20 is connected to the first phase-locked amplifier 12 to control the reference frequency input to the first phase-locked amplifier 12. Several sub-lasers in the laser box output lasers of different wavelengths through their corresponding connected controllers. After adjustment by the reflector and the beam splitter, the lasers are guided out from the light outlet of the laser box and enter the excitation optical path through the rotatable first reflector 22 located downstream of the light outlet optical path.

[0042] like Figure 3 As shown, the excitation optical path changes the propagation direction of the laser through a reflector. Specifically, the linearly polarized laser is emitted from the laser 1 and passes through a number of reflectors to enter the optical path box on the top of the microscope, wherein a first aperture 23 and a second aperture 24 are provided between the rotatable first reflector 22 and the third reflector 25 to collimate the laser. The optical path box on the top of the microscope includes a fourth reflector 26 and a fifth reflector 28 for changing the direction of the laser. At the same time, a quarter glass slide 27 is coupled to the optical path between the fourth and fifth reflectors to change the polarization direction of the laser so that the laser can be changed from linear polarization to elliptical polarization and circular polarization. The light reflected by the fifth reflector 28 passes through the second beam splitter 7 and the first beam splitter 3 in sequence to enter the internal optical path of the microscope.

[0043] The illumination light path includes a white light source 17, which is incident on the third beam splitter 8 and incident on the sample stage through the internal light path 9 of the microscope, wherein the internal light path 9 of the microscope also includes an objective lens 10 for selecting different magnifications. The excitation light, the illumination light, and the reflected light share a portion of the internal light path 9 of the microscope (i.e., the illumination light path). After the illumination light is incident, it is focused on the device sample through the internal light path of the microscope, and a portion of the reflected light enters the CCD camera 6 at the top of the microscope along the same light path. The CCD camera 6 is connected to the computer 16 to output real-time images.

[0044] like Figure 4As shown, the reflected light path is the light path of the reflected laser reflected by the sample after the laser acts on the sample stage. Specifically, the reflected laser enters the optical path box on the top of the microscope through the internal optical path of the microscope and the second beam splitter 7, is split by the first beam splitter 3 in the box, and is reflected by the sixth reflector 29 into the photodetector 5. The photodetector 5 is connected to the second phase-locked amplifier 4 to obtain a sample reflectivity signal for determining the scanning position, and the reference frequency is given by the laser 1.

[0045] The translation stage includes a stacked secondary scanning translation stage 14 and a main scanning translation stage 13. The main scanning translation stage 13 is placed below the secondary scanning translation stage 14 to perform coarse and fine adjustments on the sample position. The main scanning translation stage 13 is controlled by three motors in the x, y, and z directions and is connected to a joystick to perform coarse adjustments and focusing on the sample position. The secondary scanning translation stage 14 is connected to a computer through a controller, and the sample position can be finely adjusted in the xy plane in the software, and the micron-level scanning step length in the plane can be set.

[0046] The present invention further provides a new application method, based on the above disclosed non-destructive imaging system of spin and valley polarization signals to measure the spin signal related to the tin sulfide crystal.

[0047] Currently, no one has used CVD-grown single-layer graphene to measure spin and valley signals. The present invention grows tin sulfide crystals by physical vapor deposition and makes them into measurable devices. Specifically,

[0048] An imaging method of a lossless imaging system for spin and valley polarization signals comprises the following steps:

[0049] Step 1: Make a sample, place the sample on the sample holder with gold wire and silver glue and connect it to the sample holder pins, move the main scanning stage and the sub-scanning stage, find the position of the sample under the microscope, and focus the excitation light on the sample surface; use software to control the sub-scanning stage to move the sample in the field of view at the micrometer level, move the sample to the center of the field of view for point measurement, or perform surface scanning measurement and imaging of the sample by setting the scanning step length and the scanning time for each point.

[0050] The sample is a material with a spin-split band structure, which will produce a photoelectric signal related to helicity. When a bias current is applied at both ends of the device, when circularly polarized light is irradiated on the device, the electron spins generated by the left circularly polarized light and the right circularly polarized light are in opposite directions, and the current-induced out-of-plane spins accumulate near the two ends of the opposite channel edges of the device.

[0051] The sample in this embodiment is tin sulfide crystal. The spin-orbit coupling effect of the single-layer SnS itself makes the material itself have a spin signal, such as Figure 6As shown, the present invention grows tin sulfide crystals on a magnesium oxide substrate by physical vapor deposition, and polymethyl methacrylate in the shape of a Hall bar is made on the surface of the tin sulfide by electron beam exposure technology, and finally the grown tin sulfide crystals are etched into the required Hall bar shape. Electron beam exposure technology is used to make the electrode pattern for device measurement, and the gold electrode required for measurement is made by evaporating gold and lift-off process.

[0052] Step 2, by applying different source-drain bias voltages to the sample, changing the rotation angle of the quarter glass slide 27, using the obtained left circularly polarized light and right circularly polarized light to perform surface scanning on the same position of the sample, and subtracting the two scanned images to obtain the spin current signal diagram of the sample.

[0053] The spin signal image and reflectivity signal of tin sulfide were measured by applying different source-drain bias voltages to the sample, such as Figures 7 to 9 As shown, the reflectivity image clearly shows the edge of the tin sulfide device channel and corresponds well to the device position represented by the photovoltage image.

[0054] When a bias voltage of 1.5V is applied, a spin-related positive photovoltage appears at the left edge of the channel, and a spin-related negative photovoltage appears at the right edge of the channel. The photovoltage signals with opposite signs at the channel edge represent spin accumulation in opposite directions. By changing the direction of the bias voltage, that is, applying a bias voltage of -1.5V, the sign of the spin-related voltage at the channel edge changes accordingly. By further changing the magnitude of the bias voltage, applying bias voltages of 2V and 2.5V, the magnitude of the spin-related photovoltage at the channel edge changes accordingly, indicating that the magnitude of the spin accumulation signal is related to the magnitude of the bias voltage. The discovery of the spin signal of the tin sulfide device, and the changes in its direction and magnitude with the bias voltage, further verify the feasibility of the spin imaging method.

[0055] The present invention discloses a non-destructive imaging system for spin and valley polarization signals. By setting a micron-level high-precision XY scanning stage, the selected area can be locally scanned to achieve spatial resolution imaging of the device. The photocurrent or voltage signal is received by a phase-locked amplifier, and a more accurate acquisition result is obtained for weak signals. At the same time, it is creatively used for the measurement of tin sulfide crystals, and the spin accumulation signal at the channel edge of the tin sulfide crystal device is measured and discovered. The relationship between the spin accumulation signal and the source-drain bias current of the device is explored, and it is found that the direction and size of the spin signal are related to the direction and size of the source-drain bias current of the device.

[0056] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lossless imaging system for spin and valley polarization signals, characterized in that: It includes a laser, an excitation optical path, a reflection optical path and a translation stage; The displacement stage is provided with a sample holder (15) for fixing the sample, the sample is placed on the sample holder (15) and connected to the sample holder via a gold wire, the sample holder (15) is connected to a first lock-in amplifier (12), a second lock-in amplifier (4) and a source meter (11) via pins, and is used to display a tiny electrical signal, a sample reflectivity signal and apply a bias electrical signal respectively; The laser (1) is connected to a first lock-in amplifier (12) and a second lock-in amplifier (4) to input a reference frequency to the two lock-in amplifiers; the laser (1) emits a linearly polarized laser into an excitation light path, the laser of the excitation light path irradiates a sample, the sample reflects the laser, a portion of the reflected laser is directly fed back to a CCD camera (6) for display imaging, and another portion of the reflected laser enters a reflection light path in an optical path box at the top of a microscope, and is fed back to a photodetector (5) through a beam splitter and a reflection mirror in the reflection light path; the photodetector (5) is connected to the second lock-in amplifier (4) to obtain a sample reflection signal to determine a scanning position.

2. The non-destructive imaging system of spin and valley polarization signals according to claim 1, characterized in that: The laser (1) comprises a plurality of sub-lasers and controllers thereof integrated in a main laser box (18), an external expansion laser (19) and a controller thereof; the linearly polarized lasers emitted by the main laser box (18) and the external expansion laser (19) can enter the same excitation optical path.

3. The non-destructive imaging system of spin and valley polarization signals according to claim 2, characterized in that: The laser light emitted by the main laser box (18) directly enters the excitation optical path through a rotatable first reflector (22), wherein a chopper (20) is further provided between the expansion laser (19) and the excitation optical path, and the chopper (20) is connected to the first phase-locked amplifier (12) to control the reference frequency input to the first phase-locked amplifier (12); a plurality of sub-lasers in the main laser box (18) output laser light of different wavelengths through their correspondingly connected controllers, which are guided out from the light outlet of the laser box after adjustment by the reflector and the beam splitter, and enter the excitation optical path through the rotatable first reflector (22) located downstream of the light outlet optical path.

4. The non-destructive imaging system of spin and valley polarization signals according to any one of claims 1 to 3, characterized in that: The excitation light path changes the propagation direction and plane of the laser light through a reflector. Specifically, after being emitted from the laser (1), the linearly polarized laser light passes through the reflectors in sequence and enters the optical path box at the top of the microscope. A first aperture (23) and a second aperture (24) are provided in the middle of the optical path between the laser (1) and the reflector for collimating the laser light.

5. The non-destructive imaging system of spin and valley polarization signals according to claim 4, characterized in that: The optical path box at the top of the microscope comprises a fourth reflector (26) and a fifth reflector (28) for changing the direction of the laser. Meanwhile, a quarter glass slide (27) is coupled to the optical path between the fourth and fifth reflectors for changing the polarization direction of the laser so that the laser can be changed from linear polarization to elliptical polarization and circular polarization. The light reflected by the fifth reflector (28) passes through the first beam splitter (3) and the second beam splitter (7) and enters the internal optical path (9) of the microscope.

6. The non-destructive imaging system of spin and valley polarization signals according to claim 5, characterized in that: The reflected light path is the portion of the laser light reflected from the sample stage that enters the photodetector at the light path box on the top of the microscope after passing through the internal light path of the microscope and the second beam splitter (7). Specifically, the reflected laser light enters the light path box on the top of the microscope through the second beam splitter (7), is split by the first beam splitter (3) in the box, and is reflected by the sixth reflector (29) to enter the photodetector (5).

7. The non-destructive imaging system of spin and valley polarization signals according to claim 6, characterized in that: The displacement stage comprises a stacked main scanning displacement stage (13) and a secondary scanning displacement stage (14), which respectively perform coarse adjustment and fine adjustment on the position of a sample, wherein the main scanning displacement stage (13) is placed below the secondary scanning displacement stage (14); the main scanning displacement stage (13) controls the x, y and z directions through three motors and is connected to a rocker to perform coarse adjustment and focusing on the position of the sample; the secondary scanning displacement stage (14) is connected to a computer through a controller, and the sample position can be finely adjusted in an xy plane in software, and a micron-level scanning step length in the plane can be set.

8. The imaging method of the non-destructive imaging system of spin and valley polarization signals according to claim 7, characterized in that: The following steps are involved: Step 1: Prepare a sample, place the sample on the sample holder with gold wire and silver glue and connect it to the sample holder pin, move the main scanning stage and the secondary scanning stage, find the position of the sample under the microscope, and focus the excitation light on the sample surface; control the secondary scanning stage to move the sample in the field of view at the micrometer level based on software, move the sample to the center of the field of view for point measurement, or perform surface scanning measurement and imaging of the sample by setting the scanning step length and the scanning time of each point; Step 2, by applying different source-drain bias voltages to the sample, changing the rotation angle of the quarter glass slide (27), using the obtained left circularly polarized light and right circularly polarized light to perform surface scanning on the same position of the sample, and subtracting the two scanned images to obtain a spin current signal diagram of the sample.

9. The imaging method of a non-destructive imaging system of spin and valley polarization signals according to claim 8, characterized in that: The sample is a material with a spin-split energy band structure, which generates a photoelectric signal related to the polarization of light. When a bias current is applied to both ends of the sample, when circularly polarized light is irradiated onto the device, the electron spins generated by the left circularly polarized light and the right circularly polarized light are in opposite directions, and the current-induced out-of-plane spins accumulate near both ends of the opposite channel edges of the device, changing the rotation angle of a quarter glass slide, and using the obtained left circularly polarized light and right circularly polarized light to scan the same position of the sample, and the result of subtracting the obtained scanned images is the spin current signal of the sample.

10. The imaging method of a non-destructive imaging system of spin and valley polarization signals according to claim 9, characterized in that: The sample is a tin sulfide crystal, which is grown on a magnesium oxide substrate by a physical vapor deposition method. By applying different source-drain bias voltages to the tin sulfide crystal, an electrical signal image and a reflectivity signal of the tin sulfide are measured, and a spin current signal diagram of the tin sulfide crystal is obtained.

Images