Quantized energy level measuring device based on surface photovoltage and measuring method

Abstract

This invention discloses a device and method for measuring quantum energy levels based on surface photovoltage. The device includes: a tunable wavelength monochromatic light source module, a signal generation and modulation module, and a signal receiving and detection module. The tunable wavelength monochromatic light source module is used to convert polychromatic divergent light into monochromatic light with a tunable wavelength. The signal generation and modulation module is used for quantum energy level measurement, spin energy level measurement, and quantum energy level modulation in atmospheric or vacuum environments. The signal receiving and detection module is used to receive the photovoltage signal of the sample and obtain the dependence of photovoltage on wavelength. The device has advantages such as low cost, easy partial replacement and maintenance, and convenient functional expansion.

Description

Technical Field

[0001] This invention relates to the field of photovoltage measurement device technology, and in particular to a quantized energy level measurement device and method based on surface photovoltage. Background Technology

[0002] The advancement of the information age places higher demands on the integration, storage density, operating speed, and power consumption of electronic components. Electronic devices that rely solely on charge degrees of freedom to carry information can never overcome the physical limits of their size. Therefore, another intrinsic property of electrons—spin—has attracted considerable attention. The discovery of room-temperature high tunneling magnetoresistance (TMR) in ferromagnetic tunnel junction materials in 1995, and the subsequent landmark development of artificially synthesized magnetic materials such as dilute magnetic semiconductors, have not only rapidly propelled the formation and rapid development of the emerging disciplines of magnetoelectronics and spintronics in condensed matter physics over the past 20 years, but have also greatly promoted the research and application of magnetoresistive materials and novel spintronic devices related to spin-polarized electron transport. Currently, research focuses primarily on the generation, transport, and manipulation of spin currents in semiconductors, as well as the design of novel semiconductor spintronic devices using modern semiconductor microelectronics technology. To achieve spin manipulation and efficient spin transport, sufficiently long relaxation times and high mobility of spin are required in semiconductor devices. In recent years, among the material systems for semiconductor spintronics research, group III nitride semiconductors have attracted much attention due to their wide direct bandgap, Curie transition temperature above room temperature, and long spin relaxation time. Their excellent physical properties make them the preferred materials for developing high-frequency, high-temperature, high-power electronic devices and spintronic devices.

[0003] On the other hand, low-dimensional semiconductor structures, typically represented by semiconductor superlattices, quantum wells, quantum wires, and quantum dots, represent a new field that has been explored in recent years. They are powerfully advancing semiconductor research and applications at a new level and have become one of the most active new growth points and vital frontiers in condensed matter physics. Quantum wells are potential wells of electrons or holes composed of semiconductor materials of different compositions, exhibiting significant quantum confinement effects. They can generate artificial quantum energy levels beyond intrinsic energy levels, causing significant changes in the optoelectronic properties of devices compared to bulk materials, and are currently widely used in optoelectronic devices. The band structure of a quantum well plays a decisive role in its quantum effects. Due to the effect of spin angular momentum, quantum well energy levels have a more refined structure, meaning that each energy level contains both spin-up and spin-down eigenstates. Therefore, studying GaN-based quantum well energy levels and realizing the detection and manipulation of their refined quantum structures can provide a scientific basis for the development of group III nitride semiconductor spintronic devices, and has significant teaching and research value.

[0004] There are various methods for measuring energy levels, such as photoluminescence, cyclotron resonance absorption, and photovoltage effect. Among them, surface photovoltage spectroscopy (SPS) obtains relevant information by detecting changes in surface potential caused by illumination. It is highly sensitive to the absorption of excitation light and can conveniently characterize the exciton absorption peaks of quantum wells, with sensitivity several orders of magnitude higher than X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Since the magnitude of the surface photovoltage (SPV) is related to the number and separation of photogenerated carriers, the SPV spectrum contains a wealth of photoelectric information about the material structure, such as well-hole width, material composition, and surface and interface defect states. Furthermore, as a non-contact detection method, SPS is non-destructive to the sample morphology and is unaffected by the substrate or bulk material, making it a rapid, non-destructive, and highly sensitive testing method. Therefore, SPS has attracted much attention in materials science research and is widely used in solid surface modification, electrode surface modification, LB ultrathin films, CVD films, and epitaxial films.

[0005] Compared to photoluminescence, cyclotron resonance absorption, and photovoltage effects, the surface photovoltage method is non-destructive to sample morphology and unaffected by the substrate or bulk. Furthermore, compared to absorption spectroscopy, surface photovoltage is more sensitive and has smaller errors in measuring light absorption on semiconductor surfaces and space charge regions. However, existing surface photovoltage experimental instruments are mostly integrated units, which do not provide a clear visual representation of the physical process and do not allow for the addition or removal of components as needed, hindering the convenient and rapid control and exploration of different physical quantities. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a quantum energy level measurement device based on surface photovoltage that is inexpensive, easy to replace and repair locally, and has convenient function expansion.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a quantum energy level measurement device based on surface photovoltage, comprising:

[0008] The system comprises a tunable wavelength monochromatic light source module, a signal generation and modulation module, and a signal receiving and detection module. The tunable wavelength monochromatic light source module is used to convert polychromatic divergent light into monochromatic light with a tunable wavelength. The signal generation and modulation module is used for quantum energy level detection, spin energy level detection, and quantum energy level modulation in atmospheric or vacuum environments. The signal receiving and detection module is used to receive the photovoltage signal of the sample and obtain the dependence of photovoltage on wavelength.

[0009] A further technical solution is as follows: the adjustable wavelength monochromatic light source module includes a broadband light source, a power supply, a focusing lens, an entrance slit, a collimating objective, a blazed grating, an imaging objective, a reflecting mirror, and an exit slit. The broadband light source is powered by the power supply. The emitted polychromatic diverging light is converged and parallelized by the focusing lens, the entrance slit, and the collimating objective before being incident on the blazed grating to form a horizontally distributed colored light band. Monochromatic parallel light of different wavelengths converges at the focal point of the imaging objective after passing through the imaging objective and the reflecting mirror. The exit slit is fixed at the focal point of the imaging objective. By rotating the blazed grating, monochromatic light of different wavelengths is emitted from the slit.

[0010] A further technical solution is as follows: the signal generation and control module includes a reflector, a focusing lens, a vacuum sample box, a vacuum pump, a straight glass piston, a rubber tube, a semiconductor cooling chip, a heating resistance wire, a thermocouple, a PID temperature controller, a cooling fan, a high-temperature resistant wire, a linear polarizer, a quarter-glass slide, and a magnet; after monochromatic light exits from the slit, the reflector changes the direction of light propagation from horizontal to vertically downward, and after the focusing lens enhances the light intensity, it illuminates the sample inside the vacuum sample box, exciting a surface photovoltage; the vacuum sample box is made of a metal material with electromagnetic shielding function, and has a pre-sealed quartz glass light-transmitting hole and lead wire port, which can provide a vacuum testing environment for the sample and extract the photovoltage signal; the sample box is connected to the vacuum pump through a rubber tube and a straight glass piston to provide a vacuum testing environment for the sample.

[0011] In spin quantum level detection, a linear polarizer and a quarter-glass slide are inserted into the incident light path to convert monochromatic light into circularly polarized light. At the same time, a magnetic electrode is used to collect the generated photovoltage signal, and a magnet is assembled inside the sample box to bias the magnetic moment direction of the electrode, thereby screening electrons with specific spins and realizing the detection of spin energy levels.

[0012] During quantum energy level modulation, heating resistance wires or semiconductor cooling chips are installed in the sample box to heat or cool the sample; thermocouples and PID temperature controllers are used to measure and control the sample temperature and automatically switch the electrical appliances on and off; a vacuum pump is used to discharge gas through the air extraction port reserved on the sample box to achieve temperature control in a vacuum environment.

[0013] A further technical solution is as follows: the signal receiving and detection module includes an electric rotating platform, a stepper motor controller, a stepper motor driver, an angle sensor, a data acquisition unit, a module communication sensor, and a regulated power supply; the electric rotating platform includes a stepper motor, controlled by a matching controller and driver, which drives the rotating platform to adjust the angle of the blazed grating to obtain monochromatic light of different wavelengths at the light exit slit; the angle sensor and data acquisition unit collect photovoltage signals and analog signals corresponding to the angles, which are then converted into two digital signals by the data acquisition unit; the module communication converter is used to input electrical signals into the computer; except for the module communication converter, all electrical instruments are powered by a regulated DC power supply.

[0014] This invention also discloses a method for measuring quantized energy levels based on surface photovoltage, the method using the aforementioned apparatus, characterized in that the method includes the following steps:

[0015] Wavelength calibration;

[0016] Quantum energy level measurement;

[0017] Spin quantum energy level measurement;

[0018] And / or quantized energy level measurement and its temperature control.

[0019] The beneficial effects of adopting the above technical solution are as follows: The device described in this application has the following advantages:

[0020] Intuitive and visual: The measuring device is composed of discrete components, breaking the black box and visually demonstrating the physical process, which can deepen the understanding of physical knowledge and significantly improve hands-on skills.

[0021] Physics connotation: It integrates many fields such as optics, electricity, thermodynamics, photoelectric conversion, quantum mechanics, and semiconductor physics, and has both teaching and research functions, profoundly demonstrating the diverse forms and unified core of the discipline of physics.

[0022] Price advantage: It is much cheaper than other devices for measuring quantized energy levels, while maintaining high measurement accuracy.

[0023] Components are discrete: This facilitates partial replacement and maintenance, and also makes it easier to promote commercially.

[0024] Functional expansion: The device has good openness and functional expansion capabilities, and can be subjected to multi-field control of force, heat, light, electricity and magnetism to explore the rich physical properties of different material systems. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1This is a schematic diagram of the adjustable wavelength monochromatic light source module in the device described in this embodiment of the invention;

[0027] Figure 2 This is a schematic diagram of the signal generation and control module in the device described in this embodiment of the invention;

[0028] Figure 3 This is a schematic diagram of the signal receiving and detection module in the device described in this embodiment of the invention;

[0029] Figure 4 This refers to the photovoltage spectrum of a single-component InGaN / GaN quantum well in the method described in this embodiment of the invention.

[0030] Figure 5 These are the spin-up and spin-down photovoltage spectra of the single-component InGaN / GaN quantum well in the method described in this embodiment of the invention;

[0031] Figure 6 The photovoltage spectra of the multi-component InGaN / GaN quantum well at room temperature and high temperature (140°C) in the method described in the embodiments of the present invention;

[0032] Figure 7a The photovoltage spectra of the multi-component InGaN / GaN quantum well at room temperature and low temperature are described in the method of this invention.

[0033] Figure 7b This is a low-temperature photovoltage spectrum and its peak curve of a multi-component InGaN / GaN quantum well in the method described in the embodiments of the present invention;

[0034] The components include: 1. Broadband light source; 2. First focusing lens; 3. Light entrance slit; 4. Collimating objective lens; 5. Blazed grating; 6. Imaging objective lens; 7. Reflector; 8. Light exit slit; 9. Reflector; 10. Second focusing lens; 11. Vacuum sample box; 12. Vacuum pump; 13. Linear polarizer; 14. Quarter glass slide; 15. Magnet; 16. Sample; 17. Stepper motor controller; 18. Angle sensor; 19. Data acquisition unit; 20. Regulated power supply; 21. Electric rotating platform; 22. Computer; 23. Lead port. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] In general, this invention discloses a quantum energy level measurement device based on surface photovoltage, comprising: a tunable wavelength monochromatic light source module, a signal generation and modulation module, and a signal receiving and detection module. The tunable wavelength monochromatic light source module is used to convert polychromatic divergent light into monochromatic light with a tunable wavelength. The signal generation and modulation module is used to perform quantum energy level detection, spin energy level detection, and quantum energy level modulation in atmospheric or vacuum environments. The signal receiving and detection module is used to receive the photovoltage signal of the sample and obtain the dependence of photovoltage on wavelength.

[0038] Furthermore, such as Figure 1 As shown, the adjustable wavelength monochromatic light source module includes a broadband light source 1, a light source power supply, a first focusing lens 2, an entrance slit 3, a collimating objective lens 4, a blazed grating 5, an imaging objective lens 6, a reflecting mirror 7, and an exit slit 8. The broadband light source 1 can be a xenon lamp, or other types of broadband light sources. The xenon lamp is powered by a xenon lamp power supply and contains a high-voltage short-arc spherical xenon lamp bulb. Under high-frequency voltage excitation, it forms an arc discharge and radiates a strong and stable continuous spectrum from ultraviolet to near-infrared. The polychromatic divergent light emitted by the xenon lamp 1 is converged and paralleled by the focusing lens 2 with a focal length of 5cm, the light entrance slit 3, and the collimating objective lens 4 with a focal length of 20cm. It then enters the blazed grating 5 with a size of 5cm×5cm and a line density of 1800 lines / mm, forming a horizontally distributed colored light band. The monochromatic parallel light of different wavelengths is converged at the focal point of the imaging objective lens 6 after passing through the imaging objective lens 6 with a focal length of 20cm and the reflecting mirror 7. The light exit slit 8 is fixed at the focal point of the imaging objective lens 6. By rotating the blazed grating 5, the monochromatic light of different wavelengths is emitted from the light exit slit 8.

[0039] Compared to diffraction gratings, blazed gratings have grooves that are not parallel to the grating surface. This introduces additional phase into the incident light wave at each diffraction unit, allowing the central principal maximum of diffraction to be shifted to other interference principal maxima. Therefore, the colored light bands separated by a blazed grating have greater intensity, thus generating a larger photovoltage and improving test sensitivity. Its groove density G = 1800 mm² -1 The center wavelength is 500 nm, the incident angle and diffraction angle are i and β respectively, the diffraction order is m = 1, the wavelength range is 300 nm ≤ λ ≤ 800 nm, and the blaze angle is θ. b =26.7°. The following geometric relationships exist:

[0040] i = θ b+26.7 °

[0041] For the principal maxima of a single-slot diffraction, the incident angle is... The parallel beam satisfies:

[0042]

[0043] Optical path difference:

[0044]

[0045] Where K = ±1, ±2... represents the single-slot diffraction order;

[0046] For the principal maxima of the inter-slot interference, the incident angle is... The parallel beam satisfies:

[0047]

[0048] Optical path difference:

[0049]

[0050] Where k = 0, ±1, ±2... represents the inter-slot interference order;

[0051] Interference principal maxima:

[0052] d(sin(α+26.7)-sinβ)=d(sin(α+26.7)-sin(α-26.7))=2dcosαsinθ

[0053] =kλ

[0054] The experiment used first-order bright fringes, and we obtained:

[0055] 2dcosisinθ b =λ

[0056] Furthermore, such as Figures 2-3As shown, the signal generation and control module includes a reflector 9, a second focusing lens 10, a vacuum sample box 11, a vacuum pump 12, a straight glass piston, a rubber tube, a semiconductor cooling chip, a heating resistance wire, a thermocouple, a PID temperature controller, a cooling fan, a high-temperature resistant wire, a linear polarizer 13, a quarter-glass slide 14, and a magnet 15. After monochromatic light exits from the slit, the reflector 9 changes the direction of light propagation from horizontal to vertically downward. After the light intensity is increased by the second focusing lens 10 with a focal length of 5cm, it illuminates the sample 16 inside the vacuum sample box 11, exciting the surface photovoltage. The vacuum sample box 11 is made of a metal material with electromagnetic shielding function, and has a pre-sealed quartz glass light-transmitting hole and lead wire port 23, which can provide a vacuum testing environment for the sample and extract the photovoltage signal. The vacuum sample box 11 is connected to the 320W vacuum pump 12 through a rubber tube and a 1cm diameter straight glass piston to provide a vacuum testing environment for the sample, with an ultimate vacuum degree of approximately 0.1Pa.

[0057] A schematic diagram of measuring quantum energy levels is shown below. Figure 2 As shown, monochromatic light exits through the slit, and the reflector changes the direction of light propagation from horizontal to vertically downward. After being focused by a 5cm focal length lens to increase the light intensity, it illuminates the sample, exciting a surface photovoltage. The vacuum sample box is made of a metal material with electromagnetic shielding, and has a pre-sealed quartz glass light-transmitting hole and lead port to provide a vacuum testing environment for the sample and extract the photovoltage signal. Inside the sample box, a rubber tube and a 1cm diameter straight glass piston are connected to a 320W vacuum pump to provide a vacuum testing environment for the sample, with an ultimate vacuum of approximately 0.1Pa.

[0058] A schematic diagram of spin quantum level detection is shown below. Figure 3 As shown, a linear polarizer and a quarter-glass slide are inserted into the incident light path to convert monochromatic light into circularly polarized light. Simultaneously, a magnetic electrode collects the generated photovoltage signal, and a magnet is installed inside the sample chamber to bias the magnetic moment direction of the electrode, thereby filtering electrons with specific spins and enabling the detection of spin energy levels. A nickel-chromium alloy resistance wire or a semiconductor refrigeration device with a rated parameter of 12V-5A is installed in the sample chamber to heat or cool the sample. Thermocouples and a PID temperature controller are used to measure and control the sample temperature and automatically control the electrical circuits. A vacuum pump is used to expel gas through a pre-reserved vent on the sample chamber to achieve temperature control under vacuum conditions, preventing atmospheric convection from affecting the experimental results, thus allowing the study of quantum energy levels under room temperature, high temperature, and low temperature conditions.

[0059] like Figures 1-3As shown, the signal receiving and detection module includes an electric rotating platform 21, a stepper motor controller 17, a stepper motor driver, an angle sensor 18, a data acquisition unit 19, a module communication sensor, and a 24V regulated power supply 20. The electric rotating platform 21 includes a 42-type two-phase four-wire stepper motor, controlled by a matching controller and driver, which drives the rotating platform. The transmission ratio is 1 / 90, used to adjust the angle of the blazed grating 5 to obtain monochromatic light of different wavelengths at the light-emitting slit 8. The angle sensor 18 and the data acquisition unit 19 collect photovoltage signals and analog signals corresponding to the angles, which are then converted into two digital signals by the data acquisition unit 19. The module communication converter converts the USB serial port to an RS485 serial port and inputs the electrical signals into the computer 22. Except for the module communication converter, all electrical instruments are powered by a 24V regulated DC power supply.

[0060] Overall, the present invention also discloses a method for measuring quantized energy levels based on surface photovoltage, the method using the aforementioned apparatus, and the method comprising the following steps:

[0061] Wavelength calibration;

[0062] Quantum energy level measurement of a single-component InGaN / GaN quantum well;

[0063] Spin quantum level measurement of a single-component InGaN / GaN quantum well;

[0064] Measurement of quantized energy levels in and / or multi-component InGaN / GaN quantum wells and their temperature control.

[0065] Specific parameters to be measured:

[0066] This experiment measured the quantized energy levels and spin quantum levels of single-component and multi-component InGaN / GaN quantum well structures and performed temperature-controlled measurements. In both single-component and multi-component quantum well structures, GaN served as the quantum well barrier layer, while InGaN of different compositions served as the quantum well potential layer. The energy of electron transitions depended on the energy difference between occupied and unoccupied energy levels in the InGaN potential well.

[0067] Single-component quantum wells consist of multiple pairs of ultrathin In 0.14 Ga 0.86 The structure is composed of N / GaN, and the energy difference between the highest occupied level and the lowest unoccupied level in the potential well is: E 标 =3.106eV.

[0068] Multi-component structures containing In 0.23 Ga 0.77 N / GaN, In 0.20 Ga 0.80 N / GaN, In 0.14 Ga0.86 The energy differences between the highest occupied energy level and the lowest unoccupied energy level for the three different quantum well material compositions of N / GaN are as follows: E 1标 =3.106 eV, E 2标 =2.980eV, E 3标 = 2.917 eV. The experimental value can be compared with this nominal value in subsequent error calculations.

[0069] Wavelength calibration

[0070] The wavelength of monochromatic light obtained by the device is determined by the rotation angle of the blazed grating. Therefore, the relationship between wavelength and rotation angle should be calibrated beforehand after the device is set up. The calibration process is as follows: Start the stepper motor to continuously change the angle of the blazed grating, align the fiber of the fiber optic spectrometer used for calibration with the light output slit, and minimize the slit width as much as possible to obtain monochromatic light with better monochromaticity; read the wavelength of monochromatic light through the spectrometer, and at the same time collect the angle signal on the computer to obtain multiple sets of angle-wavelength correspondences.

[0071] Since the formula for the first-order blaze wavelength of a blazed grating is:

[0072] λ1=2dcosisinθ b

[0073] λ is the wavelength, i is the incident angle, and θ is the incident angle. b The flash angle is [blaze angle]. Considering practical situations, the formula is [formula].

[0074] λ1=2dcos(i+c)sinθ b

[0075] The specific values ​​of d and θ are not considered during calibration. b Let A≡2dsinθ b The formula simplifies to

[0076] λ1 = Acos(i + c)

[0077] By using the nonlinear function tool in Origin software to fit the corresponding values ​​of angle i and wavelength λ, the values ​​of constants A and c can be obtained.

[0078] Quantized energy level measurement - Quantized energy level measurement of single-component InGaN / GaN quantum wells:

[0079] For single-component quantum wells, the surface photovoltage spectrum at room temperature was first measured in the range of 350 nm to 500 nm. The normalized photovoltage near the peak position is shown in Table 1 below.

[0080] Table 1: Normalized photovoltage data near the peak of a single-component quantum well

[0081] Wavelength (nm) 425.5 426.0 426.5 427.0 427.5 428.0 428.5 Energy (eV) 2.914 2.911 2.907 2.904 2.901 2.897 2.894 Normalized surface photovoltage (au) 0.994 0.998 0.998 1.000 0.987 0.988 0.971

[0082] Spectral diagram as follows Figure 4 As shown, a distinct spectral peak appears at a wavelength of 404.5 nm, and the voltage values ​​on both sides of the peak decay rapidly, indicating that this peak is a quantized discontinuous transition peak with a transition energy of:

[0083]

[0084] Compared with the nominal value of 3.106 eV, the error is only 1.2%, indicating that the self-built experimental device has high testing accuracy.

[0085] Spin quantum level measurement - Spin quantum level measurement of single-component InGaN / GaN quantum well:

[0086] Under the control of a magnetic field (≈0.05T), through left-handed (σ) - ) and right-handed (σ) + When circularly polarized light is irradiated onto the sample, two photovoltage spectral lines are obtained, such as... Figure 5 As shown.

[0087] Table 2. Data near the peak position under left-handed light irradiation of a single-component quantum well.

[0088]

[0089] Table 3. Data near the peak position under right-handed light irradiation of a single-component quantum well.

[0090]

[0091] The two spectral lines correspond to spin-up and spin-down quantum energy level transitions, respectively. According to the spin polarizability formula, the following can be calculated:

[0092]

[0093] This demonstrates that the experimental setup successfully detected the spin energy level, and it is the first time that the photovoltage method has been used to achieve this measurement in a quantum well.

[0094] Quantum energy level manipulation - quantization energy level measurement and temperature control of multi-component InGaN / GaN quantum wells;

[0095] High temperature control:

[0096] First, the photovoltage spectra were measured at room temperature and 140℃. The measurement range was 390nm-540nm. The normalized photovoltages near the peak positions are shown in Table 4, and the spectral diagrams are shown below. Figure 6As shown, the high-temperature spectral lines exhibit a significant redshift compared to the room-temperature spectral lines, with the maximum redshift wavelength measured to be approximately 10 nm. This redshift phenomenon originates from the influence of temperature on the energy positions of the absorption edges. Firstly, thermal expansion, i.e., the change in the lattice constant caused by temperature, leads to the shift of the energy band edges; secondly, the change in the lattice vibration state caused by temperature results in electron-phonon coupling, causing the shift of energy level positions.

[0097] Table 4. Data near the peak position of multi-component quantum wells at room temperature.

[0098]

[0099]

[0100] Table 5. Data near the peak position of multi-component quantum well at high temperature (140℃)

[0101]

[0102] Low temperature control:

[0103] To distinguish the quantized energy levels in a multi-component quantum well, a low-temperature (-20℃) photovoltage spectrum was further detected. The measurement results were compared with those at room temperature. Figure 7a As shown, the low-temperature spectral lines exhibit more pronounced asymmetry compared to the room-temperature spectral lines, and the peak positions corresponding to the three components are clearly distinguishable, as shown in the figure. Figure 7b As shown in the figure. Further peak analysis results show that the peak wavelengths are 402.5 nm, 420.5 nm and 438.0 nm, respectively, and the normalized photovoltages near the corresponding spectral peaks are shown in Tables 6-9 below.

[0104] Table 6. Data near the peak position at low temperature for multi-component quantum wells.

[0105]

[0106] Table 7. Data on peak position near 1 in multi-component quantum wells at low temperatures.

[0107]

[0108]

[0109] Table 8. Data on peak position near 2 at low temperature in multi-component quantum wells.

[0110]

[0111] Table 9. Data on peak position near 3 in multi-component quantum wells at low temperatures.

[0112]

[0113] The calculations yield the following three quantized transition energies:

[0114]

[0115]

[0116]

[0117] Compared with the nominal value of this multi-component quantum well, the relative errors are as follows:

[0118]

[0119]

[0120]

[0121] The above results show that the quantized energy level measurement device built in this project has good energy resolution and can achieve the control of quantized energy levels under varying temperature conditions.

[0122] Instrument performance:

[0123] 1. Basic performance indicators

[0124] project Performance indicators Minimum scale division for wavelength measurement 0.3nm Wavelength test range 190nm-1100nm Photovoltage detection range 14mV-5000mV Analog voltage detection sensitivity ±1mV Signal acquisition device response time ~1ms Communication update speed ≤10Hz

Claims

1. A quantum energy level measurement device based on surface photovoltage, characterized in that, include: The system includes a tunable wavelength monochromatic light source module, a signal generation and modulation module, and a signal receiving and detection module. The tunable wavelength monochromatic light source module is used to convert polychromatic divergent light into monochromatic light with a tunable wavelength. The signal generation and modulation module is used to perform quantum energy level measurement, spin energy level measurement, and quantum energy level modulation in atmospheric or vacuum environments. The signal generation and control module includes a reflector (9), a second focusing lens (10), a vacuum sample box (11), a vacuum pump (12), a straight glass piston, a rubber tube, a semiconductor cooling chip, a heating resistance wire, a thermocouple, a PID temperature controller, a cooling fan, a high-temperature resistant wire, a linear polarizer (13), a quarter glass slide (14), and a magnet (15). After monochromatic light is emitted from the slit, the reflector (9) changes the direction of light propagation from horizontal to vertical downward. After the second focusing lens (10) increases the light intensity, it irradiates the sample (16) inside the vacuum sample box (11) and excites the surface photovoltage. The vacuum sample box (11) is made of metal material with electromagnetic shielding function, and has a pre-sealed quartz glass light-transmitting hole and lead wire port (23) to provide a vacuum testing environment for the sample and extract the photovoltage signal. The vacuum sample box (11) is connected to the vacuum pump (12) through a rubber tube and a straight glass piston to provide a vacuum testing environment for the sample. During spin quantum level detection, a linear polarizer (13) and a quarter glass plate (14) are inserted into the incident light path to convert monochromatic light into circularly polarized light. At the same time, a magnetic electrode is used to collect the generated photovoltage signal, and a magnet (15) is assembled inside the vacuum sample box (11) to bias the magnetic moment direction of the electrode, thereby screening electrons with specific spins and realizing the detection of spin energy levels. During quantum energy level modulation, a heating resistance wire or a semiconductor cooling chip is assembled in the vacuum sample box (11) to achieve sample heating or cooling; thermocouples and PID temperature controllers are used to measure and control sample temperature and automatically realize the power on and off of electrical appliances; a vacuum pump (12) is used to discharge gas through the air extraction port reserved on the sample box to achieve temperature regulation in a vacuum environment. The signal receiving and detection module is used to receive the photovoltage signal of the sample and obtain the dependence of photovoltage on wavelength.

2. The quantum energy level measurement device based on surface photovoltage as described in claim 1, characterized in that: The adjustable wavelength monochromatic light source module includes a broadband light source (1), a light source power supply, a first focusing lens (2), an entrance slit (3), a collimating objective (4), a blazed grating (5), an imaging objective (6), a reflecting mirror (7), and an exit slit (8). The broadband light source is powered by the light source power supply. The polychromatic diverging light emitted by the broadband light source (1) is converged and parallelized by the focusing lens (2), the entrance slit (3), and the collimating objective (4), and then incident on the blazed grating (5) to form a horizontally distributed colored light band. Monochromatic parallel light of different wavelengths converges at the focal point of the imaging objective (6) after passing through the imaging objective (6) and the reflecting mirror (7). The exit slit (8) is fixed at the focal point of the imaging objective (6). By rotating the blazed grating (5), monochromatic light of different wavelengths is emitted from the exit slit (8).

3. The quantum energy level measurement device based on surface photovoltage as described in claim 1, characterized in that, The signal receiving and detection module includes an electric rotating platform (21), a stepper motor controller (17), a stepper motor driver, an angle sensor (18), a data acquisition unit (19), a module communication sensor, and a regulated power supply (20). The electric rotating platform (21) includes a stepper motor, controlled by the matching controller and driver, which drives the rotating platform to adjust the angle of the blazed grating (5) to obtain monochromatic light of different wavelengths at the light exit slit (8). The angle sensor (18) and the data acquisition unit (19) collect photovoltage signals and analog signals corresponding to the angles, which are then converted into two digital signals by the data acquisition unit (19). The module communication converter is used to input electrical signals into the computer (22). Except for the module communication converter, all electrical instruments are powered by a regulated DC power supply.

4. A method for measuring quantized energy levels based on surface photovoltage, the method using the apparatus described in any one of claims 1-3, characterized in that, The method includes the following steps: Wavelength calibration; Quantum energy level measurement; Spin quantum energy level measurement; And / or quantized energy level measurement and its temperature control.

5. The method for measuring quantized energy levels based on surface photovoltage as described in claim 4, characterized in that, The wavelength calibration method includes the following steps: The stepper motor is started to continuously change the angle of the blazed grating, aligning the optical fiber of the fiber optic spectrometer used for calibration with the light output slit; the wavelength of monochromatic light is read by the spectrometer, and the angle signal is collected by the computer at the same time, so as to obtain multiple sets of angle and wavelength correspondences. Since the formula for the first-order blaze wavelength of a blazed grating is: λ1=2dcosisinθ b； λ is the wavelength, i is the incident angle, and θ is the incident angle. b Let the flare angle be the actual angle; considering practical situations, the formula is: λ1=2dcos(i+c)sinθ b； The specific values ​​of d and θ are not considered during calibration. b Let A≡2dsinθ b The formula simplifies to λ1 = Acos(i+c); By fitting the data, we obtain the corresponding values ​​of angle i and wavelength λ, and further obtain the values ​​of constants A and c.

6. The method for measuring quantized energy levels based on surface photovoltage as described in claim 4, characterized in that, The method for measuring spin quantum energy levels includes the following steps: Under magnetic field control, through left-handed σ - and right-handed σ + When circularly polarized light illuminates the sample, two photovoltage spectral lines are obtained, corresponding to spin-up and spin-down quantum energy level transitions, respectively. The results can be calculated using the spin polarizability formula: ； in denoted as the spin polarization of the photovoltage spectrum. and These are the peak voltages of the photovoltage spectra generated when the sample is irradiated with right-handed and left-handed circularly polarized light, respectively.

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