A method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function

Abstract

This invention discloses a method for calibrating the binding energy scale of indeterminate carbon peaks on a surface based on work function, comprising the following steps: obtaining the binding energy scale distribution spectrum of all elements on the sample surface through XPS full-spectrum scanning; further performing narrow-spectrum scanning on the elements on the sample surface, wherein the binding energy of the C-C / C-H peak of the indeterminate carbon C 1s on the sample surface is labeled as E. 1 BE The work function of the sample was tested using UPS, and the peak value of the C-C / C-H peak binding energy of the indeterminate carbon on the sample surface was obtained after calibration. This invention employs a combined XPS and UPS characterization method to calibrate the C 1s binding energy of the indeterminate carbon on the sample surface. This method is highly applicable to materials with unknown structures or unknown standard band gaps, and can be further extended to all systems where charge transfer at the indeterminate carbon / substrate interface is negligible.

Description

Technical Field

[0001] This invention relates to the field of binding energy scaling technology, and more particularly to a method for calibrating the binding energy scaling of surface indeterminate carbon peaks based on work function. Background Technology

[0002] X-ray photoelectron spectroscopy (XPS) is the most commonly used technique in materials science, chemistry, and biomedical engineering to assess surface chemical states, bonding structures, and surface / interface composition. Currently, calibrating elemental binding energy scales based on the C 1s spectrum of adventitious carbon (AdC) on sample surfaces is part of both ASTM (ASTM E1523-15. Standard guide to charge control and charge referencing techniques in X-ray photoelectron spectroscopy. West Conshohocken (PA): ASTM International; 2015) and ISO (ISO 19318:2004. Surface chemical analysis—reporting of methods used for charge control and charge correction) standards. However, a large number of literature reports use CC / CHC peak binding energies of exogenous adventitious carbon that are set rather arbitrarily within the range of 284.0 eV to 285.6 eV. This not only contradicts the use of the C1s energy spectrum of exogenous uncertain carbon as a standard for scaling elemental binding energies, but also suggests that inappropriate calibration of the elemental binding energy scale could lead to misinterpretations of chemical bonds. This patent employs a characterization method combining X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy (UPS), and for the first time proposes using the work function to calibrate the C1s / CH2 binding energy spectrum of uncertain carbon on the sample surface.

[0003] In vacuum or atmospheric environments, the C 1s signal formed on samples by ubiquitous exogenous carbon contamination is called an indeterminate carbon layer, which is the most common binding energy (BE) scaling reference in X-ray photoelectron spectroscopy studies. The literature “Greczynski G, Hultman L. C 1s peak of adventitious carbon aligns to the vacuum level: dire consequences for material's bonding assignment by photoelectron spectroscopy [J]. Chem. phys. chem., 2017, 18 (12): 1507-1512” mentions that they performed XPS analysis on different types of nitride films, including molybdenum nitride, vanadium nitride, tungsten nitride, titanium nitride, chromium nitride, niobium nitride, tantalum nitride, zirconium nitride, hafnium nitride, etc., and found that the binding energy (relative to the Fermi level, denoted as ) of the C 1s peak scaled as high as 1.44 eV. This is 10 times higher than the typical resolvable difference between two chemical states of the same element, making the elemental binding energy scaling reference to the C 1s peak height unreliable. To address the issue that the C / CH peak binding energies of exogenous isomorphic carbon in XPS measurements are set rather arbitrarily within the range of 284.0 eV–285.6 eV, a standardized calibration standard for the C 1s energy spectrum of surface isomorphic carbon is needed.

[0004] Patent CN112098447 B proposes a method for X-ray photoelectron spectroscopy correction using valence band spectroscopy. This method requires consulting professional literature and books to obtain the standard band gap value of the material. The difference between the standard band gap value and the tested band gap value is then shifted to obtain the true characteristic X-ray photoelectron spectrum of the material. For materials with unknown structures or unknown standard band gaps (especially multi-component compounds), the application scenarios of this method are very limited. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for scaling the binding energy of surface indeterminate carbon peaks based on work function, which is intended to overcome the shortcomings of the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function, characterized by comprising the following steps:

[0007] Step 1: Obtain the scaled distribution spectrum of binding energy of all elements on the sample surface by XPS full-spectrum scanning;

[0008] Step 2: Further narrow-spectrum scanning of the sample surface elements was performed, with the binding energy of the C1s C2C / CH2C peak of the uncertain carbon on the sample surface labeled as E. 1 BE ;

[0009] Step 3: Use a UPS to test the work function of the sample, according to E C1s BE +Φ SA =289.50 eV, the peak value of the CC / CH peak binding energy scale of the anomalous carbon on the sample surface after calibration is (289.50-Φ SA eV, defined as E 2 BE ;

[0010] Step 4: Calculate E 1 BE -E 2 BE The difference is used to obtain the scale shift value of the peak binding energy of uncertain carbon CC / CH on the sample surface;

[0011] Step 5: Based on the X-ray photoelectron spectrum calibrated with the anomalous carbon on the sample surface, the chemical state, bonding structure, and binding energy shift of the sample surface can be analyzed.

[0012] The following is a further improvement to the above technical solution:

[0013] 1. In the above scheme, in step S1, XPS is used to perform a full spectrum scan on the sample. The X-ray excitation source is AlKα rays (hv = 1486.6eV); the beam spot is 400um.

[0014] 2. In the above scheme, in step S1, the vacuum degree of the analysis chamber is better than 5.0 × 10⁻⁶. -7 mbar.

[0015] 3. In the above scheme, in step S1, the working voltage is controlled at 12kV and the filament current is controlled at 6mA.

[0016] 4. In the above scheme, in step S1, the full spectrum scanning pass energy is 100eV and the step size is 1eV.

[0017] 5. In the above scheme, in step S2, narrow-spectrum scanning of C, Zn, and Te elements is performed with a pass energy of 50 eV and a step size of 0.1 eV; the narrow spectrum is accumulated for at least 5 cycles.

[0018] 6. In the above scheme, in step S3, the UPS test uses a He resonance lamp as the excitation source.

[0019] 7. In the above scheme, the vacuum degree in step S3 is better than 10. -8 mbar.

[0020] 8. In the above scheme, in step S4, according to the magnitude of ΔE, the binding energy of other elements should be shifted according to the drift value.

[0021] 9. In the above scheme, in step S4, ΔE=E 1 BE -E 2 BE If ΔE is positive, the binding energy scale of other elements in the sample should be reduced by the drift value accordingly; if it is negative, the binding energy scale of other elements in the sample should be increased by the drift value accordingly.

[0022] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0023] 1. This invention is based on a method for scaling the binding energy of surface indeterminate carbon peaks using work function calibration. It employs a combination of XPS and UPS characterization to calibrate the C 1s binding energy of indeterminate carbon on the sample surface. This method significantly improves the accuracy of chemical state determination compared to traditional methods. This method is well-suited for materials with unknown structures or unknown standard band gaps and can be further extended to all systems where charge transfer at the indeterminate carbon / substrate interface is negligible.

[0024] 2. This invention proposes a novel method for calibrating the binding energy scale of surface uncertain carbon peaks based on the work function. Specifically, it describes a new method for calibrating the C 1s energy spectrum of surface uncertain carbon, specifically the binding energy (E) of the C 1s peak. C1s BE ) and sample work function (Φ SA The sum of these values ​​is a constant, defined as 289.50 eV; the C 1s binding energy scale of conductors and semiconductors can be calibrated by combining XPS and UPS characterization. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the binding energy of the indeterminate carbon C / CH on the sample surface;

[0026] Figure 2 High-resolution XPS spectra of Zn and Te elements after calibration for the binding energy of indeterminate carbon on the sample surface;

[0027] Figure 3 High-resolution XPS spectra of Zn and Te elements after calibration for the binding energy of indeterminate carbon on the sample surface. Implementation

[0028] The present patent can be further understood through the specific embodiments given below, but they are not intended to limit the present patent.

[0029] The present invention will be further described below with reference to embodiments:

[0030] Example 1: A method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function, comprising the following steps:

[0031] Step 1: Obtain the scaled distribution spectrum of binding energy of all elements on the sample surface by XPS full-spectrum scanning;

[0032] Step 2: Further narrow-spectrum scanning of the sample surface elements was performed, with the binding energy of the C1s C2C / CH2C peak of the uncertain carbon on the sample surface labeled as E. 1 BE ;

[0033] Step 3: Use a UPS to test the work function of the sample, according to E C1s BE + Φ SA =289.50, the peak value of the bound energy scale of the uncertain carbon CC / CH on the sample surface after calibration is (289.50-Φ SA eV, defined as E 2 BE ;

[0034] Step 4: Calculate E 1 BE -E 2 BE The difference is used to obtain the scale shift value of the peak binding energy of uncertain carbon CC / CH on the sample surface;

[0035] Step 5: Based on the X-ray photoelectron spectrum calibrated with the amorphous carbon on the sample surface, the chemical state, bonding structure, binding energy shift, etc. of the sample surface can be analyzed.

[0036] In step S1, XPS is used to perform a full-spectrum scan of the sample. The X-ray excitation source is AlKα rays (hv=1486.6eV); the beam spot is 400um.

[0037] In step S1, the vacuum level of the analysis chamber is better than 5.0 × 10⁻⁶. -7 mbar;

[0038] In step S1, the operating voltage is controlled at 12kV and the filament current is controlled at 6mA.

[0039] In step S1, the full-spectrum scan pass energy is 100 eV and the step size is 1 eV.

[0040] In step S2, narrow-spectrum scanning of C, Zn, and Te elements is performed with a pass energy of 50 eV and a step size of 0.1 eV; the narrow-spectrum elements are accumulated for at least 5 cycles.

[0041] Figure 1 The figure shows the binding energy of indeterminate carbon CC / CHC on the sample surface, EC. 1 BE It is 284.38 eV.

[0042] In step S3, the UPS test uses a He resonance lamp as the excitation source.

[0043] In step S3, the wavelength is 584 Å, the photon energy is 21.22 eV, and the vacuum level is better than 10. -8 mbar;

[0044] The work function of the sample was obtained as 5.32 eV; after work function calibration, the peak binding energy scale E of the uncertain carbon CC / CH on the sample surface was obtained. 2 BE 284.18 eV (289.50 - Φ SA =289.50 - 5.32).

[0045] Example 2: A method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function, comprising the following steps:

[0046] Step 1: Obtain the scaled distribution spectrum of binding energy of all elements on the sample surface by XPS full-spectrum scanning;

[0047] Step 2: Further narrow-spectrum scanning of the sample surface elements was performed, with the binding energy of the C1s C2C / CH2C peak of the uncertain carbon on the sample surface labeled as E. 1 BE ;

[0048] Step 3: Use a UPS to test the work function of the sample, according to E C1s BE +Φ SA =289.50 eV, the peak value of the CC / CH peak binding energy scale of the anomalous carbon on the sample surface after calibration is (289.50-Φ SA eV, defined as E 2 BE ;

[0049] Step 4: Calculate E 1 BE -E 2 BE The difference is used to obtain the scale shift value of the peak binding energy of uncertain carbon CC / CH on the sample surface;

[0050] Step 5: Based on the X-ray photoelectron spectrum calibrated with the amorphous carbon on the sample surface, the chemical state, bonding structure, binding energy shift, etc. of the sample surface can be analyzed.

[0051] In step S1, XPS is used to perform a full-spectrum scan of the sample. The X-ray excitation source is AlKα rays (hv=1486.6eV); the beam spot is 400um.

[0052] In step S1, the vacuum level of the analysis chamber is better than 5.0 × 10⁻⁶. -7 mbar;

[0053] In step S1, the operating voltage is controlled at 12kV and the filament current is controlled at 6mA.

[0054] In step S1, the full-spectrum scan pass energy is 100 eV and the step size is 1 eV.

[0055] In step S2, narrow-spectrum scanning of C, Zn, and Te elements is performed with a pass energy of 50 eV and a step size of 0.1 eV; the narrow spectrum is accumulated for at least 5 cycles.

[0056] Figure 1 The figure shows the binding energy of indeterminate carbon CC / CHC on the sample surface, EC. 1 BE It is 284.38 eV.

[0057] In step S3, the UPS test uses a He resonance lamp as the excitation source.

[0058] In step S3, the wavelength is 584 Å, the photon energy is 21.22 eV, and the vacuum level is better than 10. -8 mbar;

[0059] The work function of the sample was obtained as 5.32 eV; after work function calibration, the peak binding energy scale E of the uncertain carbon CC / CH on the sample surface was obtained. 2 BE 284.18 eV (289.50 - Φ) SA =289.50-5.32).

[0060] In step S4, the binding energies of other elements are appropriately shifted according to the drift value based on the magnitude of ΔE.

[0061] In step S4, ΔE=E 1 BE -E 2 BEIf ΔE is positive, the binding energy scale of other elements in the sample should be reduced by the drift value accordingly; if it is negative, the binding energy scale of other elements in the sample should be increased by the drift value accordingly.

[0062] Specifically, in step S4, ΔE = E 1 BE -E 2 BE =0.2eV, ΔE is a positive value, then the scaling of the binding energy of Zn and Te elements should be reduced by the drift value ΔE accordingly.

[0063] Figure 2 , Figure 3 High-resolution XPS spectra of Zn and Te elements after calibration for the binding energy of uncertain carbon on the sample surface, where, Figure 2 In the Zn 2p spectrum, the peaks at 1022 eV and 1044 eV correspond to the 2p peaks, respectively. 3 / 2 and 2p 1 / 2 The orbital indicates that the valence state of Zn is +2; Figure 3 Te 3d shown 5 / 2 and Te 3d 3 / 2 The peaks appear at binding energies of 573 eV and 583 eV (corresponding to the -2 valence state of Te), confirming the Zn-Te chemical bonding.

[0064] The above method uses a combination of XPS and UPS characterization to calibrate the C 1s binding energy of the immutable carbon on the sample surface. This method makes the accuracy of chemical state determination significantly better than traditional methods. This method is very suitable for materials with unknown structures or unknown standard band gaps, and can be further extended to all systems where the charge transfer at the immutable carbon / substrate interface is negligible.

[0065] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function, characterized in that, Includes the following steps: Step 1: Obtain the scaled distribution spectrum of binding energy of all elements on the sample surface by XPS full-spectrum scanning; Step 2: Further narrow-spectrum scanning of the sample surface elements was performed, with the binding energy of the C1s C2C / CH2C peak of the uncertain carbon on the sample surface labeled as E. 1 BE ; Step 3: Use a UPS to test the work function of the sample, according to E C1s BE +Φ SA =289.50, the peak value of the bound energy scale of the uncertain carbon CC / CH on the sample surface after calibration is (289.50-Φ SA eV, defined as E 2 BE ; Step 4: Calculate E 1 BE -E 2 BE The difference is used to obtain the scale shift value of the peak binding energy of uncertain carbon CC / CH on the sample surface; Step 5: Based on the X-ray photoelectron spectrum calibrated with the anomalous carbon on the sample surface, the chemical state, bonding structure, and binding energy shift of the sample surface can be analyzed.

2. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 1, characterized in that, In step S1, XPS is used to perform a full-spectrum scan of the sample. The X-ray excitation source is AlKα rays (hv=1486.6eV); the beam spot is 400um.

3. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 2, characterized in that, In step S1, the vacuum level of the analysis chamber is better than 5.0 × 10⁻⁶. -7 mbar.

4. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 3, characterized in that, In step S1, the operating voltage is controlled at 12kV and the filament current is controlled at 6mA.

5. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 4, characterized in that, In step S1, the full-spectrum scan pass energy is 100 eV and the step size is 1 eV.

6. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 1, characterized in that, In step S2, narrow-spectrum scanning of C, Zn, and Te elements is performed with a pass energy of 50 eV and a step size of 0.1 eV; the narrow spectrum is accumulated for at least 5 cycles.

7. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 1, characterized in that, In step S3, the UPS test uses a He resonance lamp as the excitation source.

8. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 7, characterized in that, In step S3, the vacuum level is better than 10. -8 mbar.

9. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 1, characterized in that, In step S4, the binding energies of other elements are shifted according to the drift value based on the magnitude of ΔE.

10. The method for calibrating the binding energy scale of surface indeterminate carbon peaks based on work function according to claim 9, characterized in that, In step S4, ΔE=E 1 BE -E 2 BE If ΔE is positive, the binding energy scale of other elements in the sample should be reduced by the drift value accordingly; if it is negative, the binding energy scale of other elements in the sample should be increased by the drift value accordingly.

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