A method for measuring the first electron affinity of semiconductor thin film materials

Abstract

The present invention discloses a method for measuring the first electron affinity of semiconductor thin film materials, which belongs to the field of surface and interface analysis. The measuring method includes: a calibration step, a testing step and a calculation step. The method carries a vacuum ultraviolet photoelectron spectroscopy system and a reflected photoelectron spectroscopy system in a main ultrahigh vacuum chamber. By combining the ultraviolet photoelectron spectroscopy technology with the reflected photoelectron spectroscopy technology, not only the secondary electron cutoff edge energy position and work function relative to the Fermi level can be obtained, but also the conduction band bottom position or the lowest unoccupied molecular orbital position can be obtained, and the first electron affinity value of the semiconductor thin film material can be further obtained by calculation. The measuring method is convenient, the operation process is simple, the accuracy is high, and the universality is strong.

Description

Technical Field

[0001] The invention belongs to the field of surface and interface analysis, and particularly relates to a method for measuring the first electron affinity of a semiconductor thin film material. Background Art

[0002] Surface and interface science spans many basic disciplines such as materials, energy, and information, and is the common scientific foundation for catalysis, superconductivity, and chips. The electrical, optical, and chemical properties of solids are deeply influenced by the electronic structures of their occupied and unoccupied states. In semiconductor materials, the electronic structure on both sides of the Fermi level is crucial to impurity doping, energy band regulation, and the development and application of devices, especially the unoccupied energy level structure, which directly determines the charge transfer and transport performance. Therefore, it is very important to measure the energy level structure of the unoccupied state.

[0003] The first electron affinity (E A ), also known as the first electron affinity, describes the minimum energy released when an atom or molecule gains an electron. In band theory, the first electron affinity is often used to represent the position of the conduction band bottom, E CBM Or the lowest unoccupied molecular orbital position E LUMO The energy required to reach the vacuum energy level. The first electron affinity can characterize the ability of the acceptor to accept electrons. The larger the first electron affinity, the more effectively the electrons can be injected into the acceptor conduction band or unoccupied molecular orbital, and the more conducive to the separation of excitons at the donor-acceptor interface. In a vacuum system, ultraviolet photoelectron spectroscopy can study the valence electrons or occupied molecular orbital information on the solid surface, involving the energy range between the valence band or occupied molecular orbital and the vacuum energy level; reflected photoelectron spectroscopy can study the empty electron states on the solid surface that are not occupied by electrons, mainly involving the energy range between the conduction band or unoccupied molecular orbital and the vacuum energy level. Through the complementarity of the combined technology of ultraviolet photoelectron spectroscopy and reflected photoelectron spectroscopy in the main ultrahigh vacuum system, the energy level distribution and mutual correlation near the Fermi level of semiconductor thin film materials are explored, and the establishment of a precise method for exploring the key energy level information of the first electron affinity of the surface interface becomes the key to the research.

[0004] There are two methods for obtaining the first electron affinity: theoretical calculation method and slow electron speed imaging method. Due to the different sample preparation and storage environments, the theoretical calculation values ​​will be very different, so the theoretical calculation method is not accurate and precise enough to describe the unoccupied state energy level information of semiconductor thin film materials; the slow electron speed imaging method is an experimental method, which is often used to test the first electron affinity of elements, and rarely studies semiconductor materials. In addition, the slow electron speed imager is generally built by the laboratory itself. In order to obtain high-precision and accurate imaging, the various components are expensive, and the construction process is uncontrollable. Many factors make it not very popular. Therefore, there is an urgent need for a simple, accurate, and universal measurement method to determine the first electron affinity of semiconductor thin film materials. Summary of the invention

[0005] The purpose of the present invention is to provide a method for measuring the first electron affinity of semiconductor thin film materials, which can solve the drawbacks of obtaining the first electron affinity by theoretical calculation method and slow electron speed imaging method, and the accuracy of the test results of the present invention is greatly improved.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a method for measuring the first electron affinity of a semiconductor thin film material, comprising the following steps:

[0008] Calibration steps:

[0009] The vacuum ultraviolet photoelectron spectroscopy system and the reflected photoelectron spectroscopy system are placed in the same main ultrahigh vacuum chamber, and the vacuum ultraviolet photoelectron spectroscopy spectrum and the reflected photoelectron spectroscopy spectrum are collected for the same standard sample to determine the Fermi level E of the vacuum ultraviolet photoelectron spectroscopy and the reflected photoelectron spectroscopy. F The position of the Fermi level E F After calibration, the Fermi level E F =0 eV;

[0010] Test steps:

[0011] The vacuum ultraviolet photoelectron spectroscopy system is used to collect the ultraviolet photoelectron spectroscopy spectrum of the semiconductor thin film material to be tested, and its relative to the Fermi level E F The secondary electron cutoff edge energy position E cut-off , obtain the work function W F ;

[0012] The reflected photoelectron energy spectrum system is used to collect the reflected photoelectron energy spectrum of the semiconductor thin film material to be tested, and its relative Fermi level E F The conduction band bottom position E CBM or the lowest unoccupied molecular orbital position E LUMO ;

[0013] Calculation steps:

[0014] Calculate the first electron affinity value of the semiconductor thin film material to be tested, expressed as E A =|W F |-|E CBM | or E A =|W F |-|E LUMO |.

[0015] Furthermore, the light source used in the vacuum ultraviolet photoelectron spectroscopy system is ultraviolet light with an energy of 21.22 eV; the electron acceleration voltage used in the reflected photoelectron spectroscopy system has an adjustable continuous energy of 5 to 50 eV.

[0016] Furthermore, the Fermi level E after calibration F is 0 eV, and the positive direction points to the core energy level.

[0017] Furthermore, the standard sample in the calibration step is pure metal Ni.

[0018] It is worth mentioning that pure metal Ni has a strong and steep Fermi edge, stable properties and the advantages of easy removal of surface contamination.

[0019] Furthermore, in the test step, a vacuum ultraviolet photoelectron spectroscopy system is used to collect the ultraviolet photoelectron spectroscopy spectrum of the semiconductor thin film material to be tested, and a bias voltage P of -5 to -10 eV is applied when measuring the secondary electron cutoff edge position.

[0020] It is worth noting that during the movement of photoelectrons, due to the inevitable electron-electron collision, the secondary electron cutoff edge energy position is composed of a large number of secondary electrons or energy-lost photoelectrons. Since the instrument itself has a work function, secondary electrons and low-energy electrons must overcome the instrument work function during the movement to enter the energy analyzer. Therefore, in order to allow secondary electrons or energy-lost electrons to enter the energy analyzer, a bias voltage P of -5~-10 eV is generally applied.

[0021] Furthermore, in the testing step, the relative Fermi level E F The secondary electron cutoff edge energy position E cut-off ,include:

[0022] The steep rise of the cutoff edge at the high electron binding energy of the vacuum ultraviolet photoelectron spectrum is linearly extrapolated, and its intersection with the background noise baseline is taken as the secondary electron cutoff edge energy position E cut-off .

[0023] It is worth noting that the secondary electron cutoff edge energy position corresponds to the position where the photoelectron signal detected after ultraviolet light bombards the sample surface has the highest electron binding energy in the positive direction relative to the Fermi level, that is, the photoelectron signal cutoff position corresponding to the lowest photoelectron kinetic energy.

[0024] Furthermore, the work function W F For electrons to reach the vacuum energy level E from the Fermi level vac Minimum energy required, W F =21.22-[E cut-off -P].

[0025] Furthermore, in the testing step, the relative Fermi level E F The conduction band bottom position E CBM or the lowest unoccupied molecular orbital position E LUMO ;include:

[0026] The steep rising part of the starting edge of the high electron binding energy along the reflected electron energy spectrum is linearly extrapolated, and the intersection of it and the background noise baseline is taken as the conduction band bottom position E CBM or the lowest unoccupied molecular orbital E LUMO .

[0027] It is worth noting that the conduction band bottom position E CBM or the lowest unoccupied molecular orbital E LUMO The starting position of the highest binding energy in the negative direction of the Fermi level relative to the photon signal generated by low-energy electrons of different energies injected into the surface of the sample to be tested.

[0028] Furthermore, the calibration step and the test step are performed in the same photoelectron spectrometer, and the vacuum degree of the vacuum ultraviolet photoelectron spectrometer system and the reflected photoelectron spectrometer system is better than 9*10 -7 Pa.

[0029] It is worth noting that low-energy electrons, photoelectrons, and photon signals are easily scattered by residual gas molecules, which weakens the signal intensity of the spectrum. Therefore, ultra-high vacuum technology is necessary to reduce the concentration of residual gas molecules. Only under ultra-high vacuum conditions can low-energy electrons, photoelectrons, and photons obtain a sufficiently long mean free path without being lost by scattering. Secondly, and more importantly, ultra-high vacuum environment is necessary for the surface sensitivity of surface analysis technology itself. -5 Under Pa vacuum, a monolayer of gas will be adsorbed on the solid surface in about 1 second, which is too short compared to the typical spectrum acquisition time. Therefore, an ultra-high vacuum environment is required to keep the sample surface clean during the analysis process. In an ultra-high vacuum, the surface of the material can be "atomic clean", so the test results are more consistent with the material itself. In addition, the ultraviolet light energy used in the ultraviolet photoelectron spectroscopy system is helium I, and the photon energy is 21.22 eV; the electron gun emission energy used in the inverse photoelectron spectroscopy system is less than 50 eV. Both have low energy, and the excitation process does not include core energy level excitation, so the signal distortion caused by the "relaxation process" accompanying the core energy level excitation or de-excitation can be avoided, and the accuracy of the test results is greatly improved.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The purpose of the present invention is to combine the ultraviolet photoelectron spectroscopy technology and the reflected photoelectron spectroscopy technology in an ultra-high vacuum environment, not only to obtain the relative Fermi level E F The secondary electron cutoff edge energy position E cut-off And the work function W F , we can also get the conduction band bottom position E CBM Or get the lowest unoccupied molecular orbital position E LUMO , and further obtain the first electron affinity value E of the semiconductor thin film material by calculation A This measurement method is convenient, simple to operate, highly accurate and universal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The schematic diagram of the measurement process of the first electron affinity of semiconductor thin film materials;

[0033] Figure 2 Vacuum ultraviolet photoelectron spectrum of Meo-2PACz thin film provided in an embodiment of the present invention;

[0034] Figure 3 The reflected electron spectrum of the Meo-2PACz film provided in the embodiment of the present invention;

[0035] Figure 4 The vacuum ultraviolet photoelectron spectrum of the FACsMAPbIBr film provided in the embodiment of the present invention;

[0036] Figure 5 This is the reflected electron energy spectrum of the FACsMAPbIBr film provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0038] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The present invention provides a method for measuring the first electron affinity of semiconductor thin film materials, the principle of which can be referred to Figure 1 As shown:

[0041] In vacuum ultraviolet photoelectron spectroscopy, when ultraviolet light is used to bombard the sample surface, since the energy of the ultraviolet light used is relatively low, only 21.22 eV, it can only excite electrons in the valence band or occupied molecular orbitals (at this time, the energy of the photon is greater than the electron ionization energy of this energy level. If you want to excite electrons in deep energy levels, such as core energy levels, you must use high-energy photons such as X-rays.) The electrons in the valence band or occupied molecular orbitals escape from the solid surface and enter the vacuum energy level E vac They become free electrons, i.e. photoelectrons, and then enter the energy analyzer to be detected and analyzed.

[0042] In the figure, E VBM is the top position of the valence band, E HOMO The method to determine the valence band top or the highest occupied molecular orbital position is to linearly extrapolate the steep rising part of the starting edge of the low electron binding energy of the ultraviolet photoelectron energy spectrum, and take the intersection of it with the background noise baseline as the valence band top position E VBM Or the highest occupied molecular orbital position E HOMO .

[0043] According to the molecular orbital model and Koopmans theorem, when each electron occupying the molecular orbital energy level is ionized, a band is generally generated in the ultraviolet photoelectron energy spectrum. F When 0 eV:

[0044] E k =hv-E B F -W F

[0045] Where hv is the energy of the ultraviolet photons used in vacuum ultraviolet photoelectron spectroscopy; E k is the kinetic energy of the photoelectron; E B F is the binding energy relative to the Fermi level; WF is the work function.

[0046] At high electron binding energy (low kinetic energy photoelectrons), the main source of photoelectrons is composed of a large number of secondary electrons and energy-lost electrons. Since the instrument itself has a work function, secondary electrons and low-energy electrons must overcome the instrument work function during movement to enter the energy analyzer. Therefore, in order to allow secondary electrons or energy-lost electrons to enter the energy analyzer, a bias voltage P of -5~-10 eV is generally applied. To be precise, the secondary electron cutoff edge at this time is (E cut-off -P); and the work function W F =21.22-[E cut-off -P]. Where E cut-off is the cutoff energy of secondary electrons, and P is the bias voltage.

[0047] The BIS mode (Bremsstrahlung Isochromat Spectroscopy, BIS) is often used in ultra-high vacuum system inversion electron spectroscopy. When the sample surface is bombarded with different low-energy electrons, most of them will be "captured" by the surface. The "captured" electrons enter an initial unoccupied state E of the sample. i , and then the electron transitions to another unoccupied state E f (both at the Fermi level E F Above), photons with the same energy hv are excited and undergo relaxation transition (photons are transported in the sample and then escape from the sample surface into the vacuum), which is then detected by the detector. Since this process is not affected by the sample work function, that is, the position of the Fermi level is not affected by the sample work function W F The number of photons with a certain energy corresponds to the density of empty electron states at the corresponding energy position. F is the reference energy level (E F =0 eV), linearly extrapolate the steep rising part of the starting edge of the high electron binding energy of the reflected electron energy spectrum, and take its intersection with the background noise baseline as the conduction band bottom position E CBM or the lowest unoccupied molecular orbital E LUMO .

[0048] Therefore, in an ultra-high vacuum system, we can obtain the secondary electron cutoff edge energy position E relative to the Fermi level through vacuum ultraviolet photoelectron spectroscopy. cut-off (When bias P is applied, bias P must be subtracted) and work function W F ; The bottom position of the sample conduction band can also be obtained by the reflected electron energy spectrum E CBM Or get the lowest unoccupied molecular orbital position E LUMOBy combining vacuum ultraviolet photoelectron spectroscopy and reverse photoelectron spectroscopy, the first electron affinity E of semiconductor thin film materials is further obtained. A .

[0049] The present invention provides a method for measuring the first electron affinity of a semiconductor thin film material, comprising the following steps:

[0050] Calibration steps:

[0051] The vacuum ultraviolet photoelectron spectroscopy system and the reflected photoelectron spectroscopy system are placed in the same main ultrahigh vacuum chamber, and the vacuum ultraviolet photoelectron spectroscopy spectrum and the reflected photoelectron spectroscopy spectrum are collected for the same standard sample to determine the Fermi level E of the vacuum ultraviolet photoelectron spectroscopy and the reflected photoelectron spectroscopy. F The position of the Fermi level E F After calibration, the Fermi level E F =0 eV;

[0052] Test steps:

[0053] The vacuum ultraviolet photoelectron spectroscopy system is used to collect the ultraviolet photoelectron spectroscopy spectrum of the semiconductor thin film material to be tested, and its relative to the Fermi level E F The secondary electron cutoff edge energy position E cut-off , obtain the work function W F ;

[0054] The reflected photoelectron energy spectrum system is used to collect the reflected photoelectron energy spectrum of the semiconductor thin film material to be tested, and its relative Fermi level E F The conduction band bottom position E CBM or the lowest unoccupied molecular orbital position E LUMO ;

[0055] Calculation steps:

[0056] Calculate the first electron affinity value of the semiconductor thin film material to be tested, expressed as E A =|W F |-|E CBM | or E A =|W F |-|E LUMO |.

[0057] This method relies on an X-ray photoelectron spectrometer, with a vacuum ultraviolet photoelectron spectroscopy system and a reflected photoelectron spectroscopy system in the main ultrahigh vacuum chamber. This method combines vacuum ultraviolet photoelectron spectroscopy and reflected photoelectron spectroscopy to obtain the work function W of semiconductor thin film materials. F and the conduction band bottom energy level position E CBM Or the lowest unoccupied molecular orbital energy level E LUMOBased on this, the first electron affinity E of the semiconductor thin film material is obtained. A . This measurement method is convenient, simple to operate and highly accurate. The vacuum ultraviolet photoelectron spectroscopy system and the reflected photoelectron spectroscopy system are placed in the same ultra-high vacuum environment. The concentration of gas molecules in the ultra-high vacuum environment is extremely low, which improves the accuracy of the collected test signals. In addition, since the excitation source is ultraviolet light and low-energy electrons, their energy is relatively low, and the excitation process does not include core energy level excitation. Therefore, the signal distortion caused by the "relaxation process" accompanying core energy level excitation or de-excitation can be avoided, and the accuracy of the test results is greatly improved.

[0058] The calibration step includes the following steps S1 to S5:

[0059] S1: Install the standard sample on the sample holder;

[0060] S2: The sample holder containing the standard sample is sequentially transferred to the photoelectron spectroscopy pre-evacuation chamber and the main vacuum chamber;

[0061] S3: Turn on the vacuum ultraviolet photoelectron spectroscopy system, collect the vacuum ultraviolet photoelectron spectroscopy spectrum of the standard sample Ni, and determine the Fermi level E F The position of the Fermi level E F Calibrate and turn off the UV photoelectron spectroscopy system. The Fermi level E F =0 eV.

[0062] S4: Turn on the reflected photoelectron spectroscopy system, collect the reflected photoelectron spectroscopy spectrum of the standard sample Ni, and determine the Fermi level E F The position of the Fermi level E F After calibration, the reflective electron spectroscopy system is turned off. F =0 eV.

[0063] S5: The sample holder containing the standard sample is sequentially removed from the main vacuum chamber and the pre-vacuum chamber.

[0064] The standard sample is pure metal Ni, which has a strong and steep Fermi edge, stable properties, and easy to remove surface contamination. F It is 0 eV, and the positive direction points to the core energy level, that is, in the energy state above the Fermi level, the probability of electron occupation is less than 50%, and in the energy state below the Fermi level, the probability of electron occupation is greater than 50%. The position of the Fermi level is relative to the core energy level.

[0065] The test steps include the following steps S10 to S50:

[0066] S10: Mounting a sample containing a semiconductor film to be tested on a sample holder;

[0067] S20: transferring the sample holder containing the semiconductor thin film sample to be tested to the photoelectron spectrum pre-evacuation chamber and the main vacuum chamber in sequence;

[0068] S30: Turn on the vacuum ultraviolet photoelectron spectroscopy system, apply a certain bias voltage P (e.g. -5~-10 eV), collect the vacuum ultraviolet photoelectron spectroscopy spectrum of the semiconductor film to be tested, and then turn off the vacuum ultraviolet photoelectron spectroscopy system. Obtain the secondary electron cutoff edge energy position E from the vacuum ultraviolet photoelectron spectroscopy spectrum cut-off (When bias voltage P is applied, bias voltage P needs to be subtracted.) Further, the work function W of the sample to be tested is obtained. F =21.22-[E cut-off -P]; obtained by the following method: linearly extrapolate the steep rise of the cutoff edge at the high electron binding energy of the vacuum ultraviolet photoelectron energy spectrum, and take its intersection with the background noise baseline as the secondary electron cutoff edge energy position E cut-off .

[0069] It is worth noting that the energy position of the secondary electron cutoff edge corresponds to the position where the photoelectron signal detected after ultraviolet light bombards the sample surface has the highest electron binding energy in the positive direction relative to the Fermi level, that is, the photoelectron signal cutoff position corresponding to the lowest photoelectron kinetic energy.

[0070] S40: Turn on the reflected photoelectron spectroscopy system, collect the reflected photoelectron spectroscopy spectrum of the semiconductor film to be tested, and then turn off the reflected photoelectron spectroscopy system. Obtain the conduction band bottom position E through the reflected photoelectron spectroscopy spectrum. CBM Or the lowest unoccupied molecular orbital position E LUMO It is obtained by the following method: linearly extrapolate the steep rising part of the starting edge of the high electron binding energy along the reflected electron energy spectrum, and take its intersection with the background noise baseline as the conduction band bottom position E CBM or the lowest unoccupied molecular orbital E LUMO .

[0071] It is worth noting that the conduction band bottom position E CBM or the lowest unoccupied molecular orbital E LUMO The starting position of the photon signal with the highest electron binding energy in the negative direction of the Fermi level corresponding to the photon signal generated by low-energy electrons of different energies injected into the surface of the sample to be tested.

[0072] S50: The sample tray containing the sample to be tested is sequentially removed from the main vacuum chamber and the pre-vacuum chamber.

[0073] Among them, in steps S3 and S30, the light source used by the vacuum ultraviolet photoelectron spectroscopy system is ultraviolet light with an energy of 21.22 eV; in steps S4 and S40, the electron acceleration voltage used by the reverse photoelectron spectroscopy system has an adjustable continuous energy of 5~50eV.

[0074] Calculation steps:

[0075] Work function W F and the conduction band bottom position E CBM Or the lowest unoccupied molecular orbital energy level E LUMO The difference in absolute values ​​gives the first electron affinity E A :

[0076] E A =|W F |-|E CBM |or E A =|W F |-|E LUMO |.

[0077] In an embodiment of the present invention, the method combines vacuum ultraviolet photoelectron spectroscopy and reflected photoelectron spectroscopy to obtain the work function W of the semiconductor thin film material. F and the conduction band bottom energy level position E CBM Or the lowest unoccupied molecular orbital energy level E LUMO Based on this, the first electron affinity E of the semiconductor thin film material is obtained. A The measurement method is convenient, simple to operate and highly accurate.

[0078] The measurement method of the present invention is further explained below by two examples;

[0079] Embodiment 1:

[0080] Implementation of Meo-2PAC According to the Invention Z A method for measuring the first electron affinity of a semiconductor thin film comprises the following steps:

[0081] 1) Install the Ni standard sample on the sample holder, and transfer the sample holder containing the standard sample Ni to the photoelectron spectroscopy pre-evacuation chamber and the main vacuum chamber in sequence;

[0082] 2) Turn on the vacuum ultraviolet photoelectron spectroscopy system, collect the vacuum ultraviolet photoelectron spectroscopy spectrum of the standard sample, and perform Fermi level E F Calibration of the vacuum ultraviolet photoelectron spectroscopy system is carried out.

[0083] 3) Then turn off the UV photoelectron spectroscopy system, turn on the reflected photoelectron spectroscopy system, collect the reflected photoelectron spectroscopy spectrum of the standard sample, and perform Fermi level E FAfter calibration, the energy level of the reflected photoelectron spectroscopy system is calibrated and then the reflected photoelectron spectroscopy system is turned off. F =0 eV.

[0084] 4) Move the sample holder containing the Ni standard sample out of the main vacuum chamber and the pre-vacuum chamber in turn.

[0085] 5) Will be equipped with Meo-2PAC Z The semiconductor film sample is mounted on the sample holder and the Meo-ZPAC Z The sample holder of the semiconductor film is sequentially transferred to the photoelectron spectrum pre-evacuation chamber and the main vacuum chamber;

[0086] 6) Turn on the vacuum ultraviolet photoelectron spectroscopy system, apply a -5 eV bias, and collect Meo-2PAC Z Vacuum ultraviolet photoelectron spectroscopy of semiconductor films, such as Figure 2 As shown; the vacuum ultraviolet photoelectron spectroscopy system is then turned off. Z Secondary electron cutoff edge energy position E of semiconductor film cut-off =11.82 eV; Meo-2PAC Z The work function W of semiconductor films F =21.22-[E cut-off -P]=21.22-[11.82-(-5)]=4.4 eV.

[0087] 7) Turn on the reflected electron spectroscopy system to collect Meo-2PAC Z The reflected electron spectrum of semiconductor thin films, such as Figure 3 As shown; then turn off the photoelectron spectroscopy system. Obtain Meo-2PAC Z The lowest unoccupied molecular orbital position E of the semiconductor film LUMO = -2.58 eV. Z The sample holder of the semiconductor film exits the main vacuum chamber and the pre-evacuation chamber in sequence.

[0088] 8) Therefore, Meo-2PAC Z The first electron affinity E of semiconductor thin films A =|W F |-|E LUMO |

[0089] =4.4 eV-2.58 eV=1.82 eV.

[0090] This method mainly uses the principle of photoelectric effect of ultraviolet photoelectron energy spectrum to measure the changes in the occupied state electronic structure caused by the photogenerated charge generated by ultraviolet light entering the surface of the sample under test, obtain the ultraviolet photoelectron energy spectrum, and obtain the secondary electron cutoff edge energy position E of the semiconductor film. cut-off , and further obtain the work function W of the semiconductor film F ; Using the principle of the reverse photoelectron energy spectrum and the photoelectric effect, the photon information excited by low-energy electrons entering the unoccupied state of the sample is measured to obtain the reverse photoelectron energy spectrum, and the information E of the lowest unoccupied molecular orbital of the semiconductor thin film material is detected. LUMO . Through the work function W F and the lowest unoccupied molecular orbital information E LUMO , and obtain the first electron affinity E of the semiconductor film A =|W F |-|E LUMO |.

[0091] Embodiment 2:

[0092] According to the present invention, a method for measuring the first electron affinity of a FACsMAPbIBr semiconductor film comprises the following steps:

[0093] (1) Install the Ni standard sample on the sample holder, and transfer the sample holder containing the standard sample Ni to the photoelectron spectroscopy pre-evacuation chamber and the main vacuum chamber in sequence;

[0094] (2) Turn on the vacuum ultraviolet photoelectron spectroscopy system, collect the vacuum ultraviolet photoelectron spectroscopy spectrum of the standard sample, and perform Fermi level E F Calibration of the vacuum ultraviolet photoelectron spectroscopy system is carried out.

[0095] (3) Then turn off the UV photoelectron spectroscopy system, turn on the reflected photoelectron spectroscopy system, collect the reflected photoelectron spectroscopy spectrum of the standard sample, and perform Fermi level E F After calibration, the energy level of the reflected photoelectron spectroscopy system is calibrated and then the reflected photoelectron spectroscopy system is turned off. F =0 eV.

[0096] (4) Move the sample holder containing the Ni standard sample out of the main vacuum chamber and the pre-vacuum chamber in turn.

[0097] (5) Mounting the sample containing the FACsMAPbIBr semiconductor film on the sample holder, and transferring the sample holder containing the FACsMAPbIBr semiconductor film to the photoelectron spectroscopy pre-evacuation chamber and the main vacuum chamber in sequence;

[0098] (6) Turn on the vacuum ultraviolet photoelectron spectroscopy system, apply a -5 eV bias, and collect the vacuum ultraviolet photoelectron spectroscopy spectrum of the FACsMAPbIBr semiconductor film, such as Figure 4 As shown; then the vacuum ultraviolet photoelectron spectroscopy system is turned off. The secondary electron cutoff edge energy position E of the FACsMAPbIBr semiconductor film cut-off =12.19 eV; work function W of FACsMAPbIBr semiconductor film F =21.22-[E cut-off -P]=21.22-[12.19-(-5)]=4.03 eV.

[0099] (7) Turn on the reflected photoelectron spectroscopy system and collect the reflected photoelectron spectroscopy spectrum of the FACsMAPbIBr semiconductor film, such as Figure 5 As shown, the photoelectron spectroscopy system was then turned off. Z The bottom position of the conduction band of the semiconductor film is E CBM =-0.58 eV. The sample holder containing the FACsMAPbIBr semiconductor film was removed from the main vacuum chamber and the pre-vacuum chamber in turn.

[0100] (8) Therefore, the first electron affinity E of the FACsMAPbIBr semiconductor film A =|W F |-|E CBM |

[0101] =4.03 eV -0.58 eV=3.45 eV.

[0102] This method mainly uses the principle of photoelectric effect of ultraviolet photoelectron energy spectrum to measure the changes in the valence layer electronic structure caused by the photogenerated charge generated by ultraviolet light entering the surface of the sample under test, obtain the ultraviolet photoelectron energy spectrum, and obtain the secondary electron cutoff edge energy position E of the semiconductor film. cut-off , and further obtain the work function W of the semiconductor film F ; Using the principle of the reverse photoelectron energy spectrum and the photoelectric effect, the photon information excited by the electrons entering the conduction band of the sample under test is measured to obtain the reverse photoelectron energy spectrum, and the information E of the bottom position of the conduction band of the semiconductor thin film material is detected. CBM . Through the work function W F and the information of the conduction band bottom position E CBM , and obtain the first electron affinity E of the semiconductor film A =|W F |-|E CBM |.

[0103] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for measuring the first electron affinity of a semiconductor thin film material, characterized in that: The following steps are involved: Calibration steps: The vacuum ultraviolet photoelectron spectroscopy system and the reflected photoelectron spectroscopy system are placed in the same main ultrahigh vacuum chamber, and the vacuum ultraviolet photoelectron spectroscopy spectrum and the reflected photoelectron spectroscopy spectrum are collected for the same standard sample to determine the Fermi level E of the vacuum ultraviolet photoelectron spectroscopy and the reflected photoelectron spectroscopy. F The position of the Fermi level E F After calibration, the Fermi level E F =0 eV; Test steps: The vacuum ultraviolet photoelectron spectroscopy system is used to collect the ultraviolet photoelectron spectroscopy spectrum of the semiconductor thin film material to be tested, and its relative to the Fermi level E F The secondary electron cutoff edge energy position E cut-off , obtain the work function W F ; The reflected photoelectron energy spectrum system is used to collect the reflected photoelectron energy spectrum of the semiconductor thin film material to be tested, and its relative Fermi level E F The conduction band bottom position E CBM or the lowest unoccupied molecular orbital position E LUMO ; Calculation steps: Calculate the first electron affinity value of the semiconductor thin film material to be tested, expressed as E A =|W F |-|E CBM | or E A =|W F |-|E LUMO |.

2. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 1, characterized in that: The light source used in the vacuum ultraviolet photoelectron spectroscopy system is ultraviolet light with an energy of 21.22 eV; the electron acceleration voltage used in the reflected photoelectron spectroscopy system has an adjustable continuous energy of 5 to 50 eV.

3. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 1, characterized in that: The calibrated Fermi level E F is 0 eV, and the positive direction points to the core energy level.

4. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 1, characterized in that: The standard sample in the calibration step is pure metal Ni.

5. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 2, characterized in that: In the test step, a vacuum ultraviolet photoelectron spectroscopy system is used to collect the ultraviolet photoelectron spectroscopy spectrum of the semiconductor thin film material to be tested, and a bias voltage P of -5 to -10 eV is applied when measuring the position of the secondary electron cutoff edge.

6. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 1, characterized in that: In the test step, the relative Fermi level E F The secondary electron cutoff edge energy position E cut-off ,include: The steep rise of the cutoff edge at the high electron binding energy of the vacuum ultraviolet photoelectron spectrum is linearly extrapolated, and its intersection with the background noise baseline is taken as the secondary electron cutoff edge energy position E cut-off .

7. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 5, characterized in that: The work function W F For electrons to reach the vacuum energy level E from the Fermi level vac Minimum energy required, W F =21.22-[E cut-off -P].

8. The method for measuring the first electron affinity of a semiconductor thin film material according to claim 1, characterized in that: In the test step, the relative Fermi level E F The conduction band bottom position E CBM or the lowest unoccupied molecular orbital position E LUMO ; include: The steep rising part of the starting edge of the high electron binding energy along the reflected electron energy spectrum is linearly extrapolated, and the intersection of it and the background noise baseline is taken as the conduction band bottom position E CBM or the lowest unoccupied molecular orbital E LUMO .

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