A method for measuring material ionization potential based on ultraviolet photoelectron yield spectrum

Abstract

The application provides a method for measuring material ionization potential based on ultraviolet photoelectron yield spectrum, and relates to the technical field of material analysis, and comprises the following steps: monochromatic light in a vacuum ultraviolet band is divided into a main light path for transmission and a reference light path for reflection at a target wavelength; the number of incident photons of the reference light path at the target wavelength is measured, and the number of incident photons of the main light path at the target wavelength is measured; the light splitting ratio at the target wavelength is calculated according to the number of incident photons of the main light path and the number of incident photons of the reference light path at the target wavelength; the number of photoelectrons excited by the main light path from the surface of a sample to be measured at the target wavelength is measured; the ultraviolet photoelectron yield spectrum of the sample to be measured is determined according to the light splitting ratio, the number of incident photons of the main light path and the number of photoelectrons at multiple wavelengths, and the ionization potential of the sample to be measured is determined based on the ultraviolet photoelectron yield spectrum. The application not only simplifies the measurement process of the ionization potential, but also improves the accuracy and stability of the experiment.

Description

Technical Field

[0001] This invention relates to the field of materials analysis technology, specifically to a method for measuring the ionization potential of materials based on ultraviolet photoelectron yield spectroscopy. Background Technology

[0002] In the fields of materials science, semiconductor technology, surface physics and related research, ionization potential (IP) is a core parameter characterizing the electronic structure of materials. It is defined as the minimum energy required for an electron to escape from the interior of the material to a vacuum, and directly reflects key properties of the material such as the Fermi level position, surface state distribution and electron affinity.

[0003] Currently, commonly used methods for measuring ionization potential mainly include traditional techniques such as photoelectric effect, thermal ionization, and electron spectroscopy. However, these methods are generally constrained by various factors, such as complex equipment structures, stringent sample preparation requirements, strict environmental condition control, and insufficient accuracy of data processing models. These factors collectively lead to uncertainties and errors in the measurement results, especially in the measurement of non-metallic materials (such as semiconductors and organic materials), where the problems are particularly prominent. Summary of the Invention

[0004] This invention provides a method for measuring the ionization potential of materials based on ultraviolet photoelectron yield spectroscopy, aiming to solve the problems existing in the background art. To solve the above-mentioned technical problems, this invention is implemented as follows: This invention provides a method for measuring the ionization potential of a material based on ultraviolet photoelectron yield spectroscopy, comprising: Monochromatic light in the vacuum ultraviolet band is divided into a main optical path for transmission and a reference optical path for reflection at the target wavelength, wherein the target wavelength belongs to the vacuum ultraviolet band. The number of incident photons in the reference optical path at the target wavelength is measured, and the number of incident photons in the main optical path at the target wavelength is also measured. The splitting ratio at the target wavelength is calculated based on the number of incident photons in the main optical path and the number of incident photons in the reference optical path at the target wavelength. The number of photoelectrons excited by the main optical path on the surface of the sample under test at the target wavelength is measured. The ultraviolet photoelectron yield spectrum of the sample under test is determined based on the splitting ratio at multiple wavelengths, the number of incident photons in the reference optical path, and the number of photoelectrons. The ionization potential of the sample under test is determined based on the ultraviolet photoelectron yield spectrum. The horizontal axis of the ultraviolet photoelectron yield spectrum is the photon energy corresponding to the wavelength, and the vertical axis is the photoelectron yield, which represents the number of photoelectrons generated by each incident photon.

[0005] Optionally, determining the ionization potential of the sample to be tested based on the ultraviolet photoelectron yield spectrum includes: determining a horizontal baseline with a photoelectron yield value of zero from the ultraviolet photoelectron yield spectrum through data processing; Based on a preset power function model related to the material type of the sample to be tested, the rising edge starting region of the ultraviolet photoelectron yield spectrum is fitted to obtain a fitting curve. The fitted curve is extended towards the direction of low photon energy, and its intersection with the horizontal baseline is calculated. The photon energy value corresponding to the intersection is determined as the ionization potential of the sample to be tested.

[0006] Optionally, the fitted curve is extended towards lower photon energy, and its intersection with the horizontal baseline is calculated. The photon energy value corresponding to the intersection is determined as the ionization potential of the sample to be tested, including: The first derivative of the photon energy axis of the ultraviolet photoelectron yield spectrum is calculated, and the continuous intervals where the derivative value approaches zero are identified as flat regions. The photoelectron output value within the flat area is statistically processed, and the statistical result is determined as the horizontal baseline. The fitted curve is intersected by the horizontal baseline, and the photon energy value corresponding to the intersection point is determined as the ionization potential of the sample to be tested.

[0007] Optionally, it also includes: Based on the material type of the sample to be tested, determine the excitation type and scattering type of the sample to be tested; Based on the excitation type and scattering type of the sample to be tested, a corresponding exponent value is defined for the power function model; The rising edge initiation region of the ultraviolet photoelectron yield spectrum is fitted to obtain a fitted curve, including: A nonlinear least squares fitting algorithm is used to fit the photon energy and photoelectron emission yield of the data points in the rising edge starting region to a polynomial function based on the exponent value defined by the power function model, thereby obtaining the fitting curve.

[0008] Optionally, the ultraviolet photoelectron yield spectrum of the sample to be tested is determined based on the splitting ratio at multiple wavelengths, the number of incident photons in the reference optical path, and the number of photoelectrons, including: Based on the splitting ratio at each wavelength, the number of incident photons in the reference optical path at the corresponding wavelength is corrected to obtain the actual number of incident photons in the main optical path at each wavelength. Divide the number of photoelectrons at each wavelength by the actual number of incident photons at the corresponding wavelength to obtain the photoelectron yield at each wavelength. The ultraviolet photoelectron yield spectrum curve is obtained based on the photoelectron yield values ​​at multiple wavelengths.

[0009] Optionally, the monochromatic light in the vacuum ultraviolet band is divided into a transmitted main optical path and a reflected reference optical path at the target wavelength, including: The control light source module generates monochromatic light in the vacuum ultraviolet band and processes the monochromatic light in the vacuum ultraviolet band into monochromatic light of the target wavelength; The collimating lens receives monochromatic light of the target wavelength and incidents the monochromatic light of the target wavelength parallel to the beam splitter; The beam splitter divides the monochromatic light of the target wavelength into the transmitted main optical path and the reflected reference optical path according to a preset ratio.

[0010] Optionally, the light source module includes a vacuum ultraviolet deuterium lamp, a ring mirror, a filter, and a vacuum ultraviolet monochromator; the light source module generates monochromatic light in the vacuum ultraviolet band and processes the monochromatic light in the vacuum ultraviolet band into monochromatic light of the target wavelength, including: The vacuum ultraviolet deuterium lamp is controlled to generate a continuous ultraviolet spectrum; The annular mirror reflects the light beam emitted by the vacuum ultraviolet deuterium lamp onto the filter; The filter removes stray light of non-target wavelength from the beam reflected by the annular mirror to obtain a filtered beam. The vacuum ultraviolet monochromator receives the light beam filtered by the filter and outputs monochromatic light of the target wavelength.

[0011] Optionally, measuring the number of incident photons in the reference optical path at the target wavelength includes: Using a photomultiplier tube, the number of incident photons in the reference optical path at the target wavelength is measured.

[0012] Optionally, measuring the number of incident photons in the main optical path at the target wavelength includes: The four-dimensional sample operation stage carries the sample to be tested and adjusts the spatial pose of the sample to be tested so that the main optical path is focused on the surface of the sample to be tested; An electronic shutter controls the exposure of the main optical path according to a preset exposure cycle; During the exposure of the main optical path, a wide bandgap semiconductor photodetector mounted on a movable support measures the number of incident photons in the main optical path at the target wavelength at the location of the four-dimensional sample operation stage.

[0013] Optionally, measuring the number of photoelectrons excited by the main optical path on the surface of the sample under test at the target wavelength includes: The magnetic sample transfer rod transmits the sample to be tested to the four-dimensional sample operation stage in a vacuum environment; An electron multiplier applies a high-voltage electric field to amplify the photoelectron signal excited on the surface of the sample under test; The number of photoelectrons excited by the main optical path on the surface of the sample under test is measured by a pulse counter based on the photoelectron signal amplified by the electron multiplier.

[0014] The technical solutions provided by the embodiments of the present invention bring at least the following beneficial effects: This invention employs ultraviolet photoelectron yield spectroscopy, accurately measuring the splitting ratio and photoelectron count at multiple wavelengths. This reduces the impact of equipment complexity and environmental control requirements inherent in traditional methods, improving the accuracy and repeatability of ionization potential measurements, particularly in non-metallic materials (such as organic and semiconductor materials). Through a simple optical path structure, this invention divides monochromatic light in the vacuum ultraviolet band into a main optical path and a reference optical path, achieving precise measurement of the number of incident photons and photoelectrons. This avoids the reliance on highly complex equipment and rigorous sample preparation required in traditional techniques, making the experimental operation simpler and easier to implement. Simultaneously, by precisely controlling the ultraviolet light excitation method and data acquisition process, the influence of the charging effect on the measurement results is effectively avoided, improving applicability to various materials and measurement accuracy. In summary, this invention not only simplifies the ionization potential measurement process but also improves the accuracy and stability of the experiment. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below.

[0016] Figure 1 This is a schematic diagram of the steps of a method for measuring the ionization potential of a material based on ultraviolet photoelectron yield spectroscopy, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a system for measuring the ionization potential of a material based on ultraviolet photoelectron yield spectroscopy, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of measuring the ionization potential of a material based on ultraviolet photoelectron yield spectroscopy in one embodiment of the present invention; Figure 4 This is a schematic diagram of a typical ultraviolet photoelectron yield spectrum of a sample to be tested in one embodiment of the present invention.

[0017] Labels in the diagram: 1—Vacuum UV deuterium lamp; 2—Ring mirror; 3—Filter; 4—Vacuum UV monochromator; 5—Collimating mirror; 6—Photomultiplier tube; 7—Beam splitter; 8—Electron shutter; 9—Neutralizing electron gun; 10—Electron multiplier; 11—Focusing lens; 12—Four-dimensional sample handling stage; 13—Wide bandgap semiconductor photodetector; 14—Argon ion gun; 15—Magnetic sample transfer rod. Detailed Implementation

[0018] 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 some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Currently, commonly used methods for measuring ionization potential are generally constrained by various factors, such as complex equipment structures, stringent sample preparation requirements, strict environmental condition control, and insufficient accuracy of data processing models. These factors collectively lead to uncertainties and errors in measurement results, especially in the measurement of non-metallic materials (such as semiconductors and organic materials). To address these issues, the core concept of this invention is to divide monochromatic light in the vacuum ultraviolet band into a main optical path and a reference optical path, measure the number of incident photons and photoelectrons at different wavelengths, and further perform fitting and calculation based on the ultraviolet photoelectron spectrum by combining the spectrophotometer ratio and the number of photoelectrons. This avoids interference from the charging effect, improves the accuracy and stability of non-metallic material measurements, simplifies the operation process, reduces the need for complex equipment and strict environmental control, and ultimately provides an efficient and accurate ionization potential measurement scheme.

[0020] Figure 1 This is a schematic diagram illustrating the steps of a method for measuring the ionization potential of materials based on ultraviolet photoelectron yield spectroscopy, as provided in an embodiment of the present invention. Figure 1 As shown, the method includes: Step S101: The monochromatic light in the vacuum ultraviolet band is divided into a main light path for transmission and a reference light path for reflection at the target wavelength, wherein the target wavelength belongs to the vacuum ultraviolet band.

[0021] The vacuum ultraviolet band refers to the spectrum with wavelengths in the range of 10nm to 200nm, which is a subrange of the ultraviolet spectrum. Because the photon energy in this band is relatively high, it can excite the surface of materials to generate photoelectrons. Therefore, this band is selected as the test light source in this embodiment.

[0022] Before testing, the surface of the metal sample to be tested is cleaned using an argon ion gun 14 to remove contaminants. Specifically, the argon ion gun releases argon ions to bombard the sample surface, removing any contaminants or oxides that may be present on the sample surface, thereby ensuring the cleanliness of the sample surface and providing accurate measurement results for subsequent ultraviolet photoelectron spectroscopy.

[0023] The monochromatic light generated by the vacuum ultraviolet light source is split into two independent optical paths at the target wavelength. One is the transmitted main optical path, which directly illuminates the surface of the sample under test and is used to excite photoelectrons. The other is the reflected reference optical path, which serves as a reference signal for real-time monitoring of the light source's stability and does not participate in the excitation of the sample under test. The target wavelength is the specific wavelength selected for the experiment within the vacuum ultraviolet band. In this embodiment, multiple different target wavelengths will be continuously selected within the vacuum ultraviolet band for testing to obtain the number of incident photons in the main optical path, the number of incident photons in the reference optical path, and the number of photoelectrons excited on the surface of the sample under test at multiple wavelengths. This will be described in detail later.

[0024] In an optional implementation, step S101 specifically includes steps S1011 to S1013: Step S1011: Control the light source module to generate monochromatic light in the vacuum ultraviolet band, and process the monochromatic light in the vacuum ultraviolet band into monochromatic light of the target wavelength.

[0025] Monochromatic light covering the vacuum ultraviolet band is generated by a light source module. The light source module can be a xenon lamp, deuterium lamp, or other stable light source suitable for the ultraviolet band. The selection of the target wavelength is determined based on the photoelectric properties and ionization potential measurement requirements of the material under test.

[0026] Figure 2 This is a schematic diagram of a material ionization potential measurement system based on ultraviolet photoelectron yield spectroscopy provided in one embodiment of the present invention. Please refer to [link / reference]. Figure 2 The light source module includes a vacuum ultraviolet deuterium lamp 1, a ring mirror 2, a filter 3, and a vacuum ultraviolet monochromator 4; in an optional embodiment, step S1011 specifically includes steps S10111 to S10114: Step S10111: Control the vacuum ultraviolet deuterium lamp to generate a continuous ultraviolet spectrum.

[0027] First, a vacuum ultraviolet deuterium lamp (D2 lamp) is controlled to generate a continuous ultraviolet spectrum covering the vacuum ultraviolet band. The deuterium lamp is a commonly used ultraviolet light source, particularly suitable for providing high-brightness and highly stable ultraviolet spectra. Because it can produce a broad wavelength range from 160 nm to 400 nm, the deuterium lamp provides a relatively uniform ultraviolet spectrum for experiments. In practice, the deuterium lamp is started by adjusting the power supply and control system. During emission, the deuterium lamp produces continuous ultraviolet light within the vacuum ultraviolet band. The output spectrum will include light of multiple different wavelengths.

[0028] In step S10112, the annular mirror reflects the light beam emitted by the vacuum ultraviolet deuterium lamp onto the filter.

[0029] A ring mirror is used to reflect the ultraviolet light beam from the vacuum ultraviolet deuterium lamp onto the filter. A ring mirror is an optical element used to reflect and guide light beams in the optical path. Its shape is designed so that the beam remains relatively focused and uniform after reflection by the ring mirror. The main function of the ring mirror is to concentrate the ultraviolet light emitted by the deuterium lamp and guide it to the filter for further processing.

[0030] In step S10113, the filter removes stray light of non-target wavelength from the light beam reflected by the annular mirror to obtain a filtered light beam.

[0031] Optical filters are used to remove stray light from the ultraviolet beam reflected from a ring mirror, retaining only the target wavelength. Stray light refers to extra spectral components outside the target wavelength range that may affect subsequent measurements. Filters are made of special materials that allow light to pass through a specific wavelength range while absorbing or reflecting other wavelengths. Through precise design and selection, it can be ensured that only monochromatic light matching the target wavelength passes through, while other wavelength components are effectively blocked. The filtered beam has a more uniform wavelength distribution, ensuring that the light source outputs monochromatic light close to the target wavelength. The choice of filter depends on the specific requirements of the target wavelength; for example, a bandpass filter (allowing the target wavelength while blocking other wavelengths) or high-pass / low-pass filters (allowing light greater than or less than a specific wavelength, respectively) can be used.

[0032] In step S10114, the vacuum ultraviolet monochromator receives the light beam filtered by the filter and outputs monochromatic light of the target wavelength.

[0033] The ultraviolet beam, after being processed by filters, is fed into a vacuum ultraviolet monochromator, where it is further filtered and output as monochromatic light of a specific target wavelength. A vacuum ultraviolet monochromator is a device capable of separating and outputting a specific wavelength from the spectrum; its core working principle is based on the dispersion effect of light. A vacuum ultraviolet monochromator contains optical elements such as gratings, lenses, or prisms to separate light of different wavelengths. By adjusting the angle of the grating, the desired target wavelength is selected. After the filtered beam emitted by the deuterium lamp enters the monochromator, the optical elements selectively separate the light of the desired wavelength according to the preset target wavelength, while other components outside the target wavelength range are filtered out. Through this process, the vacuum ultraviolet monochromator can output precise monochromatic light of the target wavelength for subsequent experiments or measurements.

[0034] In step S1012, the collimating lens receives monochromatic light of the target wavelength and incident the monochromatic light of the target wavelength parallel to the beam splitter.

[0035] The target wavelength monochromatic light selected by the vacuum ultraviolet monochromator 4 is received by the collimating lens 5. Located at the exit end of the vacuum ultraviolet monochromator 4, the collimating lens 5 collimates the monochromatic beam, converting it into a parallel beam. Subsequently, this parallel monochromatic beam is precisely guided and incident on the surface of the beam splitter 7, ensuring the parallelism of the light rays incident on the beam splitter 7. This lays the necessary optical foundation for the subsequent steps where the beam splitter 7 divides the beam into a transmission path and a reflection path.

[0036] In step S1013, the beam splitter divides the monochromatic light of the target wavelength into the main optical path that is transmitted and the reference optical path that is reflected, according to a preset ratio.

[0037] Beam splitter 7 distributes the focused monochromatic light of the target wavelength into the main optical path and the reference optical path according to a preset ratio. Based on the reflectivity and transmittance of the material, the beam splitter divides the incident beam into two beams, one of which passes through the transmission path to become the main optical path (e.g., ...). Figure 2 The middle beam points to the lateral optical path of the focusing lens 11, while the other beam becomes the reference optical path through the reflection path (e.g., Figure 2 The middle point is the longitudinal optical path of the photomultiplier tube 6. The beam splitting ratio is the relative proportion of photons in the two optical paths.

[0038] Step S102: Measure the number of incident photons in the reference optical path at the target wavelength, and measure the number of incident photons in the main optical path at the target wavelength.

[0039] The number of incident photons passing through the reference optical path and the main optical path at the selected target wavelength is measured. This measurement effectively reveals the photon intensity of the light source at the target wavelength, as well as the light energy transmitted through different optical paths, providing an accurate photon counting basis for subsequent experimental data analysis.

[0040] In one optional implementation, step S102 specifically includes: Step S1021: Using photomultiplier tube 6, measure the number of incident photons in the reference optical path at the target wavelength.

[0041] Photomultiplier tubes (PMTs) are used to measure the number of incident photons in a reference optical path at a target wavelength. A photomultiplier tube is a highly sensitive detector that converts incident photons into electronic signals and amplifies these electronic signals through a multiplication process, thereby enabling the detection of low-intensity signals.

[0042] Whenever a photon is absorbed by the photocathode of a photomultiplier tube, it releases electrons. These electrons are multiplied through multiple electrodes inside the photomultiplier tube, eventually generating a measurable current signal.

[0043] During this process, the photomultiplier tube counts each incident photon and converts the number of photons into a corresponding electronic signal, facilitating subsequent data processing and analysis. By comparing the output signal of the photomultiplier tube with a preset exposure period, the number of photons entering the reference optical path within a specific time period can be accurately calculated.

[0044] It is important to note that the gain (amplification factor) of the photomultiplier tube should be adjusted according to the measurement requirements to ensure that the number of photons under low light intensity conditions can be accurately measured.

[0045] In an optional implementation, step S102 further includes steps S1022 to S1024: In step S1022, the four-dimensional sample operation stage 12 carries the sample to be tested and adjusts the spatial pose of the sample to be tested so that the main optical path is focused on the surface of the sample to be tested.

[0046] The four-dimensional sample stage 12 is used to hold the sample to be tested and adjust its spatial pose so that the light beam passing through the main optical path can be precisely focused on the surface of the sample. The four-dimensional sample stage 12 has multiple degrees of freedom, allowing for translation and rotation in three directions to adjust the position and angle of the sample, ensuring that the light beam is focused on a specific location on the sample. Specifically, the sample to be tested is first placed on the four-dimensional sample stage 12 via the magnetic transfer rod 15, ensuring it is in the appropriate position. Next, the spatial pose of the sample is fine-tuned by manually or automatically adjusting the four-dimensional sample stage 12, ensuring that the light beam in the main optical path is concentrated and accurately illuminates the surface of the sample.

[0047] Step S1023: Electronic shutter, control the exposure of the main optical path according to the preset exposure cycle.

[0048] By controlling the electronic shutter 8, the exposure of the subject is controlled according to the preset exposure cycle. The electronic shutter is used to adjust the incident time of light, thereby precisely controlling the exposure duration and ensuring that the exposure time remains consistent each time.

[0049] Specifically, the main function of an electronic shutter is to periodically open and close the optical path, thereby limiting the time window for light to enter. The setting of the exposure period directly affects the measurement accuracy and signal-to-noise ratio. The exposure period should be set according to the required light intensity and the stability of the light source. It should not be too short, lest sufficient photon information cannot be collected, nor should it be too long, lest overexposure cause measurement errors or overload the photomultiplier tube.

[0050] During this process, the light source in the main optical path will begin to illuminate the light under the control of the electronic shutter, and after a preset time, the shutter will close and stop the exposure.

[0051] In step S1024, during the exposure of the main optical path, a wide bandgap semiconductor photodetector mounted on a movable support measures the number of incident photons in the main optical path at the target wavelength at the location of the four-dimensional sample operation stage.

[0052] During the exposure in the main optical path, the number of incident photons illuminating the sample surface through the main optical path is measured at the location of the four-dimensional sample operation stage 12 using a wide-bandgap semiconductor photodetector 13 mounted on a movable support. The photodetector employs a wide bandgap semiconductor material, which exhibits excellent photoelectric response characteristics at the target wavelength, enabling effective detection of photon signals in the main optical path. The wide bandgap semiconductor photodetector 13 operates by absorbing photons and converting them into an electrical signal to measure the photon count. Due to the high bandgap of wide bandgap semiconductor materials, they exhibit strong photoelectric effects in the ultraviolet, visible, and near-infrared bands, effectively detecting photon signals within the target wavelength range. The wide bandgap semiconductor photodetector 13 is mounted on a movable support, allowing its position to be adjusted according to experimental needs. After the relative positions of the four-dimensional sample stage 12 and the wide bandgap semiconductor photodetector 13 are adjusted, the wide bandgap semiconductor photodetector 13 can accurately receive incident photons in the main optical path at the target wavelength and convert them into measurable electrical signals.

[0053] Step S103: Calculate the splitting ratio at the target wavelength based on the number of incident photons in the main optical path and the number of incident photons in the reference optical path at the target wavelength.

[0054] spectral ratio This refers to a specific target wavelength. Below, the number of incident photons detected by the reference optical path The number of incident photons detected by the main optical path The ratio between them. Its mathematical expression is:

[0055] spectral ratio This reflects the beam splitter at the target wavelength. The optical beam-splitting characteristics (reflectivity to transmittance ratio) at a given wavelength. The reflection / transmission properties of the beam splitter may differ at different wavelengths, therefore... It is a function of wavelength. The splitting ratio also implicitly includes the wavelength difference between the reference optical path detector (photomultiplier tube, PMT) and the main optical path detector (wide-bandgap semiconductor photodetector). The relative response sensitivity difference at the location. Although the detector has been calibrated, The measured values ​​contain overall state information of the system at that wavelength.

[0056] In actual measurements, the output intensity of the vacuum ultraviolet deuterium lamp may fluctuate or drift slightly over time. This is because the photons in the reference and main optical paths originate from the same light source pulse (after beam splitting). and They will fluctuate proportionally. This proportional relationship is provided. In subsequent calculations of the actual number of photons irradiating the sample surface, Divide by The actual number of photons reaching the sample surface can then be obtained. More importantly, in subsequent measurements of the number of photoelectrons in the sample under test... In this way, it is not necessary to move the photodetector to the sample position for measurement every time. (This is both time-consuming and may disturb the sample position.) Only at each wavelength... Real-time measurement reference optical path And using the pre-determined wavelength point The number of photons actually reaching the sample surface at this moment and wavelength can be calculated using the following formula. That is, the actual number of incident photons in the main optical path:

[0057] In this way, even if the light source intensity fluctuates during the scanning process, the actual number of photons excited in the sample at each wavelength point can be accurately determined, thus ensuring the photoelectron yield. The accuracy of the calculations eliminates systematic errors caused by the instability of the light source.

[0058] Step S104: Measure the number of photoelectrons excited by the main optical path on the surface of the sample under test at the target wavelength.

[0059] The number of photoelectrons emitted from the surface of a sample under ultraviolet light of a target wavelength is quantified. The entire process is conducted in a vacuum environment because the behavior of photoelectrons can be affected by air molecules. Air molecules collide with electrons, causing scattering and energy loss, which in turn affects the measurement results. Therefore, the experiment must be performed in a vacuum environment to preserve the pristine state of the photoelectrons, thus ensuring high accuracy.

[0060] In an optional implementation, step S104 specifically includes steps S1041 to S1043: In step S1041, the magnetic sample transfer rod transfers the sample to be tested to the four-dimensional sample operation stage in a vacuum environment.

[0061] The sample to be tested is accurately transferred to the four-dimensional sample handling stage 12 under vacuum conditions. For this purpose, a magnetic transfer rod 15 is used as the sample transfer tool. Through the action of magnetism, precise sample transfer can be achieved while maintaining high stability. The magnetic transfer rod consists of a coil generating a strong magnetic field and a transfer device with attached magnetic material. The sample is magnetically attracted to the transfer device and transferred to the four-dimensional sample handling stage 12 under precise control.

[0062] In step S1042, the electron multiplier applies a high-voltage electric field to amplify the photoelectron signal excited on the surface of the sample under test.

[0063] The weak photoelectron signal emitted from the surface of the sample is amplified by an electron multiplier 10. An electron multiplier is a precision electronic device that enhances the photoelectron signal emitted from the sample surface by applying a high-voltage electric field, making it more prominent and easier for subsequent counting. An electron multiplier typically consists of multiple multiplier tubes, each containing a cathode and multiple gain electrodes. Electrons generated by the photoelectric effect first strike the cathode of the multiplier, releasing primary electrons. These primary electrons are then accelerated and strike the gain electrodes in the multiplier, generating more secondary electrons. This process is repeated continuously at the multiple gain electrodes of the electron multiplier, ultimately amplifying the weak photoelectron signal into a sufficiently strong electrical signal. By applying a high-voltage electric field, the electron multiplier can control the acceleration and collision process of electrons, effectively amplifying the photoelectron signal.

[0064] In practice, by setting the step size and scanning range of the vacuum ultraviolet monochromator, and turning on the high-voltage power supply of the electron multiplier (for example, the input / output / anode voltages are set to 500V / 1900V / 2100V respectively), the incident light wavelength is continuously adjusted. The number of incident photons and photoelectrons collected are recorded, and the ultraviolet photoelectron yield spectrum of the sample can be obtained by calculation through the background software.

[0065] Step S1043: Using a pulse counter, based on the photoelectron signal amplified by the electron multiplier, measure the number of photoelectrons excited by the main optical path on the surface of the sample under test.

[0066] The number of photoelectrons excited by the main optical path on the surface of the sample under test is obtained by accurately measuring the photoelectron signal amplified by the electron multiplier using a pulse counter.

[0067] A pulse counter is a high-precision counting device. Its working principle is to convert the electrical signal amplified by an electron multiplier into a pulse signal. Each time a photoelectron passes through the counter, the counter records a pulse. These pulse signals are digitized and analyzed by a computer system. The pulse counter ultimately outputs the measured number of photoelectrons. That is, the number of photoelectrons excited on the surface of the sample by the main optical path. .

[0068] In one optional embodiment, a material ionization potential measurement system based on ultraviolet photoelectron yield spectroscopy provided by one embodiment of the present invention further includes a helium lamp and a neutralizing electron gun 9; A helium lamp is a calibration light source in the vacuum ultraviolet band. In this embodiment, the helium lamp is used as the incident light source, with an energy of 21.2 eV, corresponding to a wavelength of approximately 58.5 nm.

[0069] The neutralizing electron gun 9 is located near the four-dimensional sample operating stage 12. In order to achieve electron neutralization on the surface of the insulating material, the neutralizing electron gun 9 emits a low-energy electron beam to neutralize the charge, ensuring that the photoelectron yield measurement is not disturbed, and cleaning the surface of the sample to be measured before measurement.

[0070] Step S105: Based on the splitting ratio at multiple wavelengths, the number of incident photons in the main optical path, and the number of photoelectrons, determine the ultraviolet photoelectron yield spectrum of the sample to be tested, and determine the ionization potential of the sample to be tested based on the ultraviolet photoelectron yield spectrum. The horizontal axis of the ultraviolet photoelectron yield spectrum is the photon energy corresponding to the wavelength, and the vertical axis is the photoelectron yield, which characterizes the number of photoelectrons generated by each incident photon.

[0071] This invention constructs an ultraviolet photoelectron yield spectrum (PYS) by integrating optical parameters and photoelectron data. Specifically, the incident wavelength... Converted into photon energy The formula corresponding to the abscissa of the ultraviolet photoelectron yield spectrum is:

[0072] In the formula, h It is Planck's constant. c It's the speed of light. Calculate the photoelectron yield. The formula corresponding to the ordinate of the ultraviolet photoelectron yield spectrum is:

[0073] in,

[0074] therefore:

[0075] For ultraviolet photoelectronic production Y Based on the physical meaning of the three-step photoelectric emission model, it is believed that:

[0076] in, Vacuum level energy, Represents the energy of the incident photon Excite electrons to energy The probability of:

[0077] in, M fi For the transition matrix elements, and ρ f The electronic densities of states for the initial and final states are respectively, and the function is... X (E) describes the probability of electrons being transported from the interior of a solid to the surface, and is usually related to the electron's inelastic mean free path. λ (E) is related and can be approximately expressed in an exponential decay form: For electrons in energy levels E The transmission probability on Let be the surface escape probability. and These represent the matrix products of the initial and final state densities, respectively. The ultraviolet photoelectron yield helps observe fine structures near the threshold region. Therefore, the threshold energy is determined by fitting a curve within the threshold region using a hypothetical function. Under certain conditions, the ultraviolet photoelectron yield exhibits power-law properties. IP For metallic samples, m=2; for inorganic semiconductor materials, m=1 or 2; considering the surface photoelectron emission process, m=1, 3 / 2, 2, 5 / 2; the ionization potential IP is determined by material adaptive fitting.

[0078] In an optional implementation, step S105 specifically includes steps S1051 to S1053: Step S1051: Determine the horizontal baseline with a photoelectron yield value of zero from the ultraviolet photoelectron yield spectrum through data processing.

[0079] In this embodiment, the horizontal baseline represents the reference state where, theoretically, the photoelectron yield should be zero when the photon energy is below the material ionization potential. However, in actual measurements, due to factors such as electronic noise, stray light interference, or detector dark counts, the measured photoelectron yield value may exhibit a slight non-zero background. Therefore, this invention proposes to objectively determine the horizontal baseline from the ultraviolet photoelectron yield spectrum using data processing methods.

[0080] Specifically, for the acquired ultraviolet photoelectron yield spectrum curves, the energy range where the photon energy is significantly lower than the estimated ionization potential was selected. Within this range, the photoelectron yield changes very little with photon energy, theoretically approaching zero. Statistical analysis was performed on all photoelectron yield data points within this range, and the calculated results were used as the horizontal baseline of the ultraviolet photoelectron yield spectrum. The horizontal baseline represents the background noise level of the system under the current experimental conditions.

[0081] Step S1052: Based on a preset power function model related to the material type of the sample to be tested, the rising edge starting region of the ultraviolet photoelectron yield spectrum is fitted to obtain a fitting curve.

[0082] According to the photoelectric emission theory, near the ionization potential threshold, the photoelectron yield Y and the incident photon energy hv satisfy a power-law relationship. Different materials (such as metals, inorganic semiconductors, and organic semiconductors) and different photoelectron emission processes (such as bulk emission, surface emission, direct / indirect optical excitation, and elastic / inelastic scattering) correspond to different values ​​of m.

[0083] Based on the photoelectron emission process of the sample under test, the exponent m value is retrieved from a preset rule. See Table 1 for an example of the preset rule: Table 1. Exponent m values ​​for different photoelectric emission processes

[0084] Users can select material categories, match m-values, and embed them into the model through the software interface. (C is the proportionality coefficient).

[0085] In the ultraviolet photoelectron yield spectrum, the rising edge initiation region was selected, i.e., the continuous interval where the photoelectron yield first shows a significant increase from near the horizontal baseline. A nonlinear least squares fitting algorithm was used to fit the data points (photon energy, photoelectron yield) within this region based on the determined power function model. A linear fit was performed with photon energy as the independent variable and photoelectron yield as the dependent variable to obtain the fitted curve. The fitted curve describes the trend of photoelectron yield with photon energy near the ionization potential threshold.

[0086] In an optional implementation, steps S10521 to S10522 are further included: Step S10521: Determine the excitation type and scattering type of the sample to be tested based on the material type of the sample to be tested.

[0087] The electron emission behavior of a material is determined by its physical properties, which must be considered in conjunction with the following characteristics: material type, microstructure, and electronic state properties. As shown above, the user inputs the material type and structural parameters through the software interface, and based on this, the excitation type and scattering type are determined (e.g., inputting "direct bandgap semiconductor and high defect concentration" will output "direct optical excitation and elastic scattering").

[0088] Step S10522: Define the corresponding exponent value for the power function model based on the excitation type and scattering type of the sample to be tested.

[0089] Based on the rules shown in Table 1, the output results are mapped to the exponent m. For example, if the input material type is metal and the excitation type is bulk emission, the scattering type is determined to be elastic scattering, and m=2 is determined.

[0090] In the ultraviolet photoelectron yield spectrum, a polynomial fitting is performed on the rising edge initiation region, and a portion is extracted from the yield spectrum. The first significant increase in a continuous interval linearizes the power function relationship:

[0091] by As the independent variable, Optimize parameters as dependent variable The ionization potential IP is used to generate the fitted curve.

[0092] In one optional implementation, step S1052 specifically includes: A nonlinear least squares fitting algorithm is used to fit the photon energy and photoelectron emission yield of the data points in the rising edge starting region to a polynomial function based on the exponent value defined by the power function model, thereby obtaining the fitting curve.

[0093] As mentioned earlier, optoelectronic output With photon energy The relationship is:

[0094] In the ultraviolet photoelectron yield spectrum, only the initial segment of the rising edge (i.e., the initial curve region where the yield increases from zero) is selected, excluding interfering data from the high-energy segment. A least-squares optimization algorithm is used to substitute the yield data and photon energy data into a preset power function model. Specifically, while maintaining the previously selected exponent values, the ionization potential and proportionality coefficient are adjusted. Through error minimization calculations, the fitted curve is made to fit the measured data points as closely as possible, and the final output fitted curve is obtained under convergence.

[0095] Step S1053: The fitted curve intersects with the horizontal baseline extension, and the photon energy value corresponding to the intersection point is determined as the ionization potential of the sample to be tested.

[0096] Extend the fitted curve towards lower photon energies and calculate its intersection with the horizontal baseline. Since the horizontal baseline represents a zero photoelectron yield and the fitted curve represents the growth behavior of the yield near the threshold, the intersection of the two physically corresponds to the minimum photon energy, i.e., the ionization potential, at which the material just begins to emit photoelectrons.

[0097] In practice, a horizontal baseline (a straight line parallel to the photon energy axis, with the ordinate value being the statistical result determined in step S1051) and a fitted curve (obtained from step S1052) can be plotted in the same coordinate system. By analytical solution or numerical approximation, the photon energy value corresponding to when the function value of the fitted curve equals the horizontal baseline value is found, and this intersection point is the ionization potential.

[0098] Figure 3 This is a schematic diagram illustrating the measurement of material ionization potential based on ultraviolet photoelectron yield spectroscopy in one embodiment of the present invention. Please refer to [link / reference]. Figure 4 The horizontal baseline is taken from the low-energy region of the ultraviolet photoelectron yield spectrum, representing the mean background noise when there is no photoelectron emission. The experimental data points are the measured yield values ​​in the rising edge initiation region. The fitted curve is the result of fitting a power function to the data points. The finally determined ionization potential (IP) is the intersection of the fitted curve and the horizontal baseline, with its energy value marked by a vertical dashed line.

[0099] In an optional implementation, step S1053 specifically includes steps S10531 to S10532: Step S10531: Perform first derivative calculation on the photon energy axis of the ultraviolet photoelectron yield spectrum, and identify the continuous interval where the derivative value approaches zero as a flat region.

[0100] First, the first derivative of the obtained ultraviolet photoelectron yield spectrum curve is calculated. Let the ultraviolet photoelectron yield spectrum be a function. ,in Photon energy, This refers to the output of optoelectronic products. (Calculation) right The first derivative. In the low-energy region, where the photon energy is significantly lower than the material's ionization potential, the photoelectron yield hardly changes with the photon energy, and its derivative value approaches zero. Therefore, by scanning the entire photon energy axis, a continuous interval where the absolute value of the derivative is less than a preset threshold is identified; this interval is the flat region. The flat region corresponds to the part of the ultraviolet photoelectron yield spectrum where the yield change is the most gradual, located at the low-energy beginning of the spectrum.

[0101] Step S10532: Perform statistical processing on the photoelectron output value in the flat area, and determine the statistical result as the horizontal baseline.

[0102] Since theoretically there should be no photoelectron emission in flat regions, the measured small yield values ​​mainly originate from system background noise. To obtain a horizontal baseline value, statistical processing is performed on all photoelectron yield values ​​within the flat regions. Statistical methods can include calculating the arithmetic mean, median, or mode. Preferably, the arithmetic mean is used as the horizontal baseline value to balance the influence of random noise. The statistical result is the horizontal baseline, which is considered the benchmark for zero photoelectron yield in subsequent calculations. In the ultraviolet photoelectron yield spectrum, the horizontal baseline is represented as a straight line parallel to the photon energy axis, with its ordinate value being the statistical result.

[0103] Step S10533: The fitted curve intersects with the horizontal baseline extension, and the photon energy value corresponding to the intersection point is determined as the ionization potential of the sample to be tested.

[0104] Since the horizontal baseline represents the background noise benchmark with no photoelectron emission, and the fitted curve represents the power-law behavior of photoelectron yield with increasing photon energy near the threshold, the intersection of the two physically corresponds to the minimum photon energy, i.e., the ionization potential, at which the material just begins to emit photoelectrons. In practice, the horizontal baseline is expressed as a constant function. Express the fitted curve as a function Solving the equation analytically Obtain photon energy value If the fitted function is in power function form, then the analytical solution is:

[0105] The photon energy value corresponding to the intersection point is determined as the ionization potential of the sample to be tested, so as to realize the automatic identification of the horizontal baseline and the objective determination of the ionization potential.

[0106] In an optional implementation, step S105 further includes steps S1054 to S1056: Step S1054: Based on the splitting ratio at each wavelength, the number of incident photons in the main optical path at the corresponding wavelength is corrected to obtain the actual number of incident photons in the main optical path at each wavelength.

[0107] Actual number of incident photons ( The result is obtained through correction to eliminate the influence of the system's spectrophotometric ratio. Step S103 has already been described in detail and will not be repeated here.

[0108] Step S1055: Divide the number of photoelectrons at each wavelength by the actual number of incident photons at the corresponding wavelength to obtain the photoelectron yield value at each wavelength.

[0109] Optoelectronic output ( The photoemission efficiency (PAE) is defined as the number of photoelectrons excited by each incident photon, reflecting the photoemission efficiency of a material at a specific wavelength. The calculation formula is:

[0110] Step S1056, based on the photoelectron yield values at multiple wavelengths, obtain the ultraviolet photoelectron yield spectrum curve.

[0111] Sort the photoelectron yields at multiple wavelengths ( , ,…, ) according to the photon energy ( Y ( ) to form a data set: hv )

[0112] With the photon energy ( , unit: eV) as the abscissa and the photoelectron yield (Y, unit: number of photoelectrons / photon) as the ordinate, plot the ultraviolet photoelectron yield spectrum curve.

[0113] In the ultraviolet photoelectron yield spectrum curve, it includes a low-energy region, that is, the region where the yield is close to zero ( <IP), a rising-edge region, that is, the region where the yield increases significantly with the increase of photon energy ( ≈IP), and a high-energy region, that is, the region where the yield tends to saturate or grow linearly ( IP). Observe the starting point of the rising edge and preliminarily estimate the ionization potential range.

[0114] Figure 4 is a schematic diagram of the typical ultraviolet photoelectron yield spectrum of the sample to be measured in an embodiment of the present invention. Please refer to Figure 4 , in the ultraviolet photoelectron yield spectrum of the material gold Au, the curve shows an "S"-shaped rising trend and is divided into three key regions. The first is the low-energy region (left platform). In the low-energy region, the photon energy is lower than the ionization potential (IP), and the photoelectron yield approaches zero (horizontal baseline). The second is the rising-edge region (middle steep rise section). In the rising-edge region, the photon energy is close to IP, and the photoelectron yield increases according to a power law with the increase of energy. The third is the high-energy region (right gentle section). The photon energy is significantly higher than IP, and the photoelectron yield tends to saturate or grow linearly.

[0115] This invention employs ultraviolet photoelectron yield spectroscopy, accurately measuring the splitting ratio and photoelectron count at multiple wavelengths. This reduces the impact of equipment complexity and environmental control requirements inherent in traditional methods, improving the accuracy and repeatability of ionization potential measurements, particularly in non-metallic materials (such as organic and semiconductor materials). Through a simple optical path structure, this invention divides monochromatic light in the vacuum ultraviolet band into a main optical path and a reference optical path, achieving precise measurement of the number of incident photons and photoelectrons. This avoids the reliance on highly complex equipment and rigorous sample preparation required in traditional techniques, making the experimental operation simpler and easier to implement. Simultaneously, by precisely controlling the ultraviolet light excitation method and data acquisition process, the influence of the charging effect on the measurement results is effectively avoided, improving applicability to various materials and measurement accuracy. In summary, this invention not only simplifies the ionization potential measurement process but also improves the accuracy and stability of the experiment.

[0116] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, electronic devices, and media. Therefore, embodiments of the present invention can take the form of entirely hardware embodiments, entirely software embodiments, or embodiments combining software and hardware aspects. Furthermore, embodiments of the present invention can take the form of a computer program product embodied on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0117] Embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods and apparatus according to embodiments of the present invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0118] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0119] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the term "comprising" or any other variations thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element. The above provides a detailed description of a material ionization potential measurement method based on ultraviolet photoelectron yield spectroscopy provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and its core ideas; at the same time, for those skilled in the art, based on the ideas of the present invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for measuring the ionization potential of a material based on ultraviolet photoelectron yield spectroscopy, characterized in that, include: Monochromatic light in the vacuum ultraviolet band is divided into a main optical path for transmission and a reference optical path for reflection at the target wavelength, wherein the target wavelength belongs to the vacuum ultraviolet band. The number of incident photons in the reference optical path at the target wavelength is measured, and the number of incident photons in the main optical path at the target wavelength is also measured. The splitting ratio at the target wavelength is calculated based on the number of incident photons in the main optical path and the number of incident photons in the reference optical path at the target wavelength. The number of photoelectrons excited by the main optical path on the surface of the sample under test at the target wavelength is measured. The ultraviolet photoelectron yield spectrum of the sample under test is determined based on the splitting ratio at multiple wavelengths, the number of incident photons in the reference optical path, and the number of photoelectrons. The ionization potential of the sample under test is determined based on the ultraviolet photoelectron yield spectrum. The horizontal axis of the ultraviolet photoelectron yield spectrum is the photon energy corresponding to the wavelength, and the vertical axis is the photoelectron yield, which represents the number of photoelectrons generated by each incident photon.

2. The method according to claim 1, characterized in that, Determining the ionization potential of the sample based on the ultraviolet photoelectron yield spectrum includes: From the ultraviolet photoelectron yield spectrum, a horizontal baseline with a photoelectron yield value of zero is determined through data processing; Based on a preset power function model related to the material type of the sample to be tested, the rising edge starting region of the ultraviolet photoelectron yield spectrum is fitted to obtain a fitting curve. The fitted curve is extended towards the direction of low photon energy, and its intersection with the horizontal baseline is calculated. The photon energy value corresponding to the intersection is determined as the ionization potential of the sample to be tested.

3. The method according to claim 2, characterized in that, Extend the fitted curve towards lower photon energy, calculate its intersection with the horizontal baseline, and determine the photon energy value corresponding to the intersection as the ionization potential of the sample to be tested, including: The first derivative of the photon energy axis of the ultraviolet photoelectron yield spectrum is calculated, and the continuous intervals where the derivative value approaches zero are identified as flat regions. The photoelectron output value within the flat area is statistically processed, and the statistical result is determined as the horizontal baseline. The fitted curve is intersected by the horizontal baseline extension, and the photon energy value corresponding to the intersection point is determined as the ionization potential of the sample to be tested.

4. The method according to claim 2, characterized in that, Also includes: Based on the material type of the sample to be tested, determine the excitation type and scattering type of the sample to be tested; Based on the excitation type and scattering type of the sample to be tested, a corresponding exponent value is defined for the power function model; The rising edge initiation region of the ultraviolet photoelectron yield spectrum is fitted to obtain a fitted curve, including: A nonlinear least squares fitting algorithm is used to fit the photon energy and photoelectron emission yield of the data points in the rising edge starting region to a polynomial function based on the exponent value defined by the power function model, thereby obtaining the fitting curve.

5. The method according to claim 1, characterized in that, The ultraviolet photoelectron yield spectrum of the sample under test is determined based on the dispersive ratio at multiple wavelengths, the number of incident photons in the reference optical path, and the number of photoelectrons, including: Based on the splitting ratio at each wavelength, the number of incident photons in the reference optical path at the corresponding wavelength is corrected to obtain the actual number of incident photons in the main optical path at each wavelength. Divide the number of photoelectrons at each wavelength by the actual number of incident photons at the corresponding wavelength to obtain the photoelectron yield at each wavelength. The ultraviolet photoelectron yield spectrum curve is obtained based on the photoelectron yield values ​​at multiple wavelengths.

6. The method according to claim 1, characterized in that, Monochromatic light in the vacuum ultraviolet band is divided into a transmitted main optical path and a reflected reference optical path at the target wavelength, including: The control light source module generates monochromatic light in the vacuum ultraviolet band and processes the monochromatic light in the vacuum ultraviolet band into monochromatic light of the target wavelength; The collimating lens receives monochromatic light of the target wavelength and incidents the monochromatic light of the target wavelength parallel to the beam splitter; The beam splitter divides the monochromatic light of the target wavelength into the transmitted main optical path and the reflected reference optical path according to a preset ratio.

7. The method according to claim 6, characterized in that, The light source module includes a vacuum ultraviolet deuterium lamp, a ring mirror, a filter, and a vacuum ultraviolet monochromator; the light source module generates monochromatic light in the vacuum ultraviolet band and processes the monochromatic light in the vacuum ultraviolet band into monochromatic light of the target wavelength, including: The vacuum ultraviolet deuterium lamp is controlled to generate a continuous ultraviolet spectrum; The annular mirror reflects the light beam emitted by the vacuum ultraviolet deuterium lamp onto the filter; The filter removes stray light of non-target wavelength from the beam reflected by the annular mirror to obtain a filtered beam. The vacuum ultraviolet monochromator receives the light beam filtered by the filter and outputs monochromatic light of the target wavelength.

8. The method according to claim 1, characterized in that, Measuring the number of incident photons in the reference optical path at the target wavelength includes: Using a photomultiplier tube, the number of incident photons in the reference optical path at the target wavelength is measured.

9. The method according to claim 1, characterized in that, Measuring the number of incident photons in the main optical path at the target wavelength includes: The four-dimensional sample operation stage carries the sample to be tested and adjusts the spatial pose of the sample to be tested so that the main optical path is focused on the surface of the sample to be tested; An electronic shutter controls the exposure of the main optical path according to a preset exposure cycle; During the exposure of the main optical path, a wide bandgap semiconductor photodetector mounted on a movable support measures the number of incident photons in the main optical path at the target wavelength at the location of the four-dimensional sample operation stage.

10. The method according to claim 9, characterized in that, Measuring the number of photoelectrons excited by the main optical path on the surface of the sample under test at the target wavelength includes: The magnetic sample transfer rod transmits the sample to be tested to the four-dimensional sample operation stage in a vacuum environment; An electron multiplier applies a high-voltage electric field to amplify the photoelectron signal excited on the surface of the sample under test; The number of photoelectrons excited by the main optical path on the surface of the sample under test is measured by a pulse counter based on the photoelectron signal amplified by the electron multiplier.

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