Method for high-pressure regulation of photoelectric performance of molybdenum diselenide

Abstract

The application discloses a high-pressure regulation method of photoelectric performance of molybdenum diselenide. The method is characterized in that: the molybdenum diselenide sample is placed in a diamond anvil cell high-pressure cavity, a hydrostatic pressure of 0.4-3.9 GPa is applied under the premise of keeping the structure of 2H phase stable, the band gap is reduced to 0.77 eV and the light absorption is enhanced by using the lattice shrinkage, and the photoelectric current is significantly improved. Under the pressure of 3.9 GPa, the photoelectric current is improved by 2 times compared with that in the normal pressure state; when the pressure is more than 4 GPa, the photoelectric response disappears due to the increase of the dark current. The application combines the in-situ X-ray diffraction, Raman spectrum and infrared reflection spectrum in a wide pressure range to characterize the structure evolution and optical property change of the material, and combines the photoelectric current test and the first principle calculation to clarify the mechanism of the high-pressure induced photoelectric performance enhancement, and establishes the physical correlation of pressure-lattice shrinkage-band gap reduction-photoelectric current enhancement, thereby providing a technical basis for the regulation of photoelectric detection materials in a high-pressure environment.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic materials technology, specifically, it relates to a high-voltage control method for the optoelectronic properties of molybdenum diselenide. Background Technology

[0002] Molybdenum diselenide (MoSe2), a typical transition metal chalcogenide semiconductor material, possesses excellent photoelectric conversion properties and has significant application potential in the field of photoelectric detection. Currently, methods for modulating its photoelectric properties mainly include chemical doping, strain engineering, and heterostructure construction. However, these methods often suffer from problems such as complex processes, poor uniformity of control, or difficulty in achieving precise in-situ control, which limits its application in photoelectric detection in extreme environments.

[0003] High pressure, as an extreme physical condition, can effectively control the crystal structure and electronic properties of materials. Although the high-pressure photoelectric properties of MoS2 and WS2, which are related materials, have been studied, the Se atoms in MoSe2 have larger atomic radii, lower electronegativity, and significantly stronger spin-orbit coupling strength compared to S atoms. This results in unique interlayer coupling characteristics, defect state distribution, and high-pressure photoelectric response behavior, which cannot be predicted from the high-pressure behavior of existing TMDs materials. Summary of the Invention

[0004] Existing high-pressure research on TMDs materials mainly focuses on high-pressure-induced structural phase transitions and their impact on photoelectric properties, while research on finely controlling photoelectric properties through interlayer coupling within a pressure window without structural phase transitions is relatively limited. This invention differs from the aforementioned research paradigm, achieving a significant improvement in photoelectric properties in MoSe2 without structural phase transitions, thus expanding the technical approach for high-pressure control of material properties.

[0005] To address the shortcomings of the existing technology, the present invention aims to provide a high-voltage control method for the photoelectric performance of molybdenum diselenide. This invention can significantly improve the photocurrent of molybdenum diselenide through high-voltage control.

[0006] The high-voltage control method includes: placing a molybdenum diselenide sample in a diamond anvil cell high-voltage chamber and applying hydrostatic pressure to cause the molybdenum diselenide (MoSe2) to undergo lattice contraction, reduce the band gap, and enhance light absorption, thereby increasing the photocurrent.

[0007] Preferably, the effective pressure for photoelectric performance regulation is 0.4-3.9 GPa.

[0008] More preferably, the pressure is 3.9 GPa, at which point the photocurrent increases by about 2 times compared to the normal pressure state (from about 70 nA to about 125 nA).

[0009] It should be noted that when the pressure exceeds 4 GPa, the dark current increases sharply with the pressure and overwhelms the photocurrent signal, causing the photoelectric response to disappear; however, the molybdenum diselenide maintains the 2H phase structure (P63 / mmc space group) in the range of 0-10 GPa and does not undergo structural phase transition.

[0010] The molybdenum diselenide sample is in bulk or powder form, with a lattice constant a of 3.288 Å and a lattice constant c of 12.911 Å under normal pressure.

[0011] Secondly, this invention also provides a molybdenum diselenide photoelectric material obtained in the range of 0.4-4 GPa using the above-mentioned high-pressure control method. The material maintains a 2H phase structure, with lattice constants a and c decreasing monotonically with pressure. The band gap decreases from 1.24 eV to 0.77 eV, and the light absorption capacity is significantly enhanced in the near-infrared band. The photocurrent is increased by 50%-200% compared to the ambient pressure state. The characteristics of the material are confirmed by the following characterization methods:

[0012] Structural stability characterization steps: Under a high-pressure environment of 0-10 GPa, the molybdenum diselenide sample was subjected to high-pressure X-ray diffraction tests. The lattice constant a monotonically decreased from 3.288 Å to 3.216 Å (at 10.6 GPa), the lattice constant c monotonically decreased from 12.911 Å to 12.101 Å (at 10.6 GPa), and the unit cell volume decreased from 120.777 Å. 3 Reduced to 108.397 Å 3 The overall compression rate was 10.2%.

[0013] Lattice dynamics characterization steps: Under a high pressure environment of 0-10 GPa, the molybdenum diselenide (MoSe2) sample was subjected to high pressure Raman spectroscopy to monitor the blue shift of the characteristic vibrational modes of A1g and E2g, confirming that the interlayer coupling increases with pressure.

[0014] Optical property characterization steps: The molybdenum diselenide sample was subjected to high-pressure near-infrared reflectance spectroscopy under a high-pressure environment of 0.8-9.4 GPa; as the pressure increased, the reflectance showed an overall upward trend, and the integrated intensity increased monotonically, confirming the reduction of the band gap and the enhancement of light absorption capacity.

[0015] Photoelectric performance characterization steps: In situ photocurrent testing was performed on the molybdenum diselenide sample under a high pressure environment of 0.4-4.8 GPa; Under periodic switching illumination conditions, the photocurrent showed good stability and repeatability, and the photocurrent amplitude gradually increased with increasing pressure, reaching a maximum value at 3.9 GPa.

[0016] Thirdly, this invention elucidates the physical mechanism of the high-voltage regulation. Through first-principles band structure calculations, it determines the bandgap reduction mechanism caused by the conduction band bottom moving closer to the Fermi level. The bandgap is 1.24 eV at ambient pressure, decreasing to 0.77 eV at 3.9 GPa: the static high pressure reduces the interlayer distance of molybdenum diselenide, enhances interlayer coupling, increases electron wavefunction overlap, and causes the conduction band bottom to move closer to the Fermi level, resulting in bandgap narrowing. This bandgap reduction enhances light absorption, thereby increasing the concentration of photogenerated carriers and significantly enhancing the photocurrent.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) High structural stability: It maintains the 2H phase structure in a wide pressure range of 0-10 GPa without structural phase change, providing a structural basis for high-voltage optoelectronic applications; (2) Clear control range: Effective control of photoelectric performance is achieved within the range of 0.4-4 GPa (it fails due to dark current flooding when it exceeds 4 GPa, but the structure remains stable). (3) Significant performance improvement: approximately 2 times increase in photocurrent at 3.9 GPa; (4) The mechanism is clear and the material is unique: A complete physical picture of MoSe2 was established, which is “lattice shrinkage → interlayer coupling enhancement → band gap reduction → light absorption enhancement → photocurrent enhancement”. The performance failure critical point caused by the sharp increase of dark current at 4 GPa is unique to MoSe2 and is different from the continuous response behavior of other TMDs materials. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an in-situ high-voltage photocurrent assembly device.

[0019] Figure 2 The images show the morphology and composition of molybdenum diselenide (MoSe2) samples, where (a) is a scanning electron microscope image, (b) is the energy dispersive spectroscopy (EDS) analysis result, and (c) is a transmission electron microscope (TEM) image.

[0020] Figure 3 The results are the in-situ X-ray diffraction characterization results under high pressure, where (a) is the X-ray diffraction pattern under different pressures, (b) is the relationship between normalized lattice parameters and pressure, and (c) is the cell volume evolution curve with pressure.

[0021] Figure 4 The results are high-pressure in-situ Raman spectra, where (a) are Raman spectra under different pressures and (b) are the relationship between the displacement of characteristic vibration modes and pressure.

[0022] Figure 5 The results are high-pressure in-situ near-infrared reflectance spectra, where (a) is the reflectance spectrum under different pressures and (b) is the relationship between integrated reflectance intensity and pressure.

[0023] Figure 6 The results are the high-pressure in-situ photocurrent test results, where (a) is the photocurrent time response curve under different pressures, and (b) is the relationship between photocurrent and pressure.

[0024] Figure 7 The figures show the theoretical calculation results. (a) shows the calculated band structure under different pressures (0 GPa and 4 GPa), which shows that the conduction band bottom moves closer to the Fermi level, causing the band gap to decrease from 1.24 eV to 0.77 eV. (b) shows the calculated light absorption spectrum under different pressures (0-4 GPa), which shows that the light absorption increases with increasing pressure. Detailed Implementation

[0025] The following examples illustrate the preferred embodiments proposed in this invention.

[0026] Figure 1 This is a schematic diagram of an in-situ high-voltage photocurrent assembly device.

[0027] Example 1

[0028] Molybdenum diselenide (MoSe2) material purchased from Shenzhen Six Carbon Technology Co., Ltd. was selected as the research object, and the material was characterized under normal pressure, as follows:

[0029] The material was characterized by scanning electron microscopy, such as Figure 2 As shown in (a), the results show that the material exhibits a layered stacking characteristic, with a complete structure and uniform lateral dimensions;

[0030] The obtained materials were subjected to energy dispersive spectroscopy analysis, such as... Figure 2 As shown in (b), the results show that the atomic percentage of Mo to Se is approximately 1:1.95, which is close to the theoretical stoichiometric ratio of 1:2, and the elemental distribution is uniform.

[0031] The obtained material was characterized by transmission electron microscopy, such as... Figure 2 As shown in (c), the results show that the lattice fringes are clear and continuous, and the interplanar spacing is regular;

[0032] The obtained material was refined by X-ray diffraction using GSASII software, confirming that the material has a 2H phase structure, space group P63 / mmc, and lattice constants a = 3.288 Å and c = 12.911 Å.

[0033] Furthermore, molybdenum diselenide (MoSe2) material and ruby ​​pressure calibrators were encapsulated in a diamond anvil cell high-pressure chamber, with silicone oil or argon as the pressure transmission medium; in-situ high-pressure XRD testing was performed using synchrotron X-rays at a wavelength of 0.5491 Å and a pressure range of 0-10.6 GPa.

[0034] X-ray diffraction patterns under different pressures are as follows: Figure 3 As shown in (a), the XRD data is refined using Rietveld, as follows: Figure 3 As shown in (b), the lattice constant a monotonically decreases from 3.288 Što 3.216 Š(at 10.6 GPa), and the lattice constant c monotonically decreases from 12.911 Što 12.101 Š(at 10.6 GPa); fitting is performed using the third-order Birch-Murnaghan equation of state, as shown in (b). Figure 3 As shown in (c), the bulk elastic modulus was 69 GPa, and the unit cell volume decreased from 120.777 ų to 108.397 ų. Analysis of the obtained spectrum confirmed that no structural phase transition occurred in the range of 0-10.6 GPa, and the 2H phase structure was maintained.

[0035] Furthermore, molybdenum diselenide (MoSe2) material was encapsulated in a diamond anvil cell high-pressure chamber for in-situ high-pressure Raman testing, with an excitation wavelength of 532 nm and a pressure range of 0.7-10.2 GPa.

[0036] Raman spectral results under different pressures are as follows Figure 4 As shown in (a) in the figure; the characteristic vibration modes of A1g and E2g were monitored, and the peak position was recorded as a function of pressure. The results are as follows. Figure 4 As shown in (b), it was observed that as the pressure increased, both the A1g and E2g peaks continuously blue-shifted towards higher wavenumbers, and the A1g mode was more sensitive to pressure than the E2g mode; it was confirmed that the 2H phase structure remained stable in the range of 0-10.2 GPa.

[0037] Furthermore, molybdenum diselenide material was encapsulated in a diamond anvil cell high-pressure chamber for in-situ high-pressure near-infrared reflectance spectroscopy testing, with a pressure range of 0.8-9.4 GPa and a wavelength range of 1300-2500 nm.

[0038] Record the reflectance spectra under different pressures, and the results Figure 5 As shown in (a), reflectivity increases with increasing pressure; the integral reflection intensity is calculated, and the results are as follows. Figure 5 As shown in (b), the results show that the integral intensity increases monotonically with pressure, confirming the decrease in band gap and the enhancement of light absorption capacity.

[0039] Furthermore, a (platinum)Pt dual-electrode structure was constructed in a diamond anvil cell device, with molybdenum diselenide (MoSe2) material placed between the electrodes; in-situ high-voltage photocurrent testing was performed using a xenon lamp as the light source, with a pressure range of 0.4-4.8 GPa.

[0040] The test was conducted under periodically switched illumination conditions, and the results are as follows: Figure 6As shown in (a) and (b), the photocurrent increased with increasing pressure; the relationship between photocurrent and pressure was observed; the photocurrent reached a maximum value of about 125 nA at 3.9 GPa, which is about twice that of about 70 nA at normal pressure; it was observed that when the pressure exceeded 4 GPa, the dark current increased sharply, causing the photoelectric response to disappear.

[0041] Furthermore, density functional theory (DFT) was used to calculate the electronic structure of molybdenum diselenide (MoSe2) under high pressure using Cambridge Sequential Total Energy Package (CASTEP) software. The exchange-correlation functional was the Perdew-Burke-Ernzerhof (PBE) functional under the generalized gradient approximation (GGA), and an ultrasoft pseudopotential was used to describe the atomic potential. Hydrostatic pressure was applied during the calculations, and a plane-wave basis set was used to determine the lowest energy configuration. The self-consistent field energy convergence criterion was set to below 5 × 10⁻⁶. -6 eV / atom, the maximum atomic force convergence criterion is set to 0.01 eV / Å, the calculation pressure range is 0-4 GPa, and the step size is 1.0 GPa;

[0042] like Figure 7 As shown, the band gap decreased from 1.24 eV at 0 GPa to 0.77 eV at 4 GPa, confirming that the conduction band bottom is approaching the Fermi level. Calculations of the optical absorption spectra under different pressures (0-4 GPa) show that the optical absorbance increases with increasing pressure.

[0043] In summary, this invention combines in-situ X-ray diffraction, Raman spectroscopy, and infrared reflectance spectroscopy over a wide pressure range to characterize the structural evolution and optical property changes of materials, as well as photocurrent testing and first-principles calculations. It elucidates the mechanism of high-pressure induced photoelectric performance enhancement, establishes the physical correlation between pressure, lattice contraction, bandgap reduction, and photocurrent enhancement, and provides a technical basis for the regulation of photoelectric detection materials in high-pressure environments.

Claims

1. A high-voltage modulation method for the photoelectric properties of molybdenum diselenide, wherein molybdenum diselenide is a transition metal chalcogenide semiconductor material; characterized in that, The high-pressure control method includes: placing a molybdenum diselenide sample with a 2H phase structure in a static high-pressure environment; applying a hydrostatic pressure of 0.4-3.9 GPa while maintaining the stability of the 2H phase structure and preventing structural phase transition; utilizing the unique interlayer coupling response characteristics of molybdenum diselenide (MoSe2) to reduce the band gap of the molybdenum diselenide from 1.24 eV to 0.77 eV, thereby enhancing light absorption and increasing the photocurrent compared to the normal pressure state.

2. The high-voltage control method according to claim 1, characterized in that, The pressure is 3.9 GPa, the band gap of the molybdenum diselenide decreases from 1.24 eV to 0.77 eV, and the photocurrent increases by 2 times compared to the normal pressure state.

3. The high-voltage control method according to claim 1, characterized in that, The static high-pressure environment is provided by a diamond anvil cell.

4. The high-voltage control method according to claim 1, characterized in that, The molybdenum diselenide sample is in bulk or powder form, with a lattice constant a of 3.288 Å and a lattice constant c of 12.911 Å under normal pressure.

5. The high-voltage control method according to claim 1, characterized in that, The molybdenum diselenide maintains a 2H phase structure within a pressure range of 0-10 GPa, and the 0.4-3.9 GPa range represents an effective window for controlling photoelectric performance.

6. The high-voltage control method according to claim 1, characterized in that, The pressure upper limit of 0.4-3.9 GPa was determined by monitoring the sharp increase in dark current. When the pressure exceeds 4 GPa, the dark current overwhelms the photocurrent signal, causing the photoelectric response to disappear. This pressure window was determined by monitoring the dark current-pressure response relationship unique to MoSe2. When the pressure exceeds 4 GPa, the dark current increases sharply and overwhelms the photocurrent signal. This critical behavior is related to the interlayer coupling characteristics and defect state distribution of MoSe2.

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