Preparation method of large-area vanadium disulfide film, photoelectric detector and application
By using high-temperature annealing and low-pressure chemical vapor deposition techniques to prepare vanadium disulfide thin films on sapphire substrates, the problem of large-area thin film growth has been solved, enabling the preparation of high-quality thin films and their efficient application in photodetectors.
Patent Information
- Application Number
- CN202511163145.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-19
- Publication Date
- 2025-12-12
AI Technical Summary
Existing technologies make it difficult to prepare high-quality, large-area vanadium disulfide thin films, and polymorphs are easily formed during the growth process, which hinders their widespread application in electronic devices.
Vanadium disulfide thin films were grown on sapphire substrates using high-temperature annealing pretreatment and low-pressure chemical vapor deposition. By controlling the precursor position and atmosphere conditions, the substrate was kept in a sulfur-rich state. A three-channel carrier gas delivery system and a low-pressure environment were used to avoid the use of hydrogen and halide salts, thus producing continuous and uniform vanadium disulfide thin films.
The prepared vanadium disulfide thin film is of excellent quality, exhibiting high responsivity and stable photoconductivity, making it suitable for photodetectors in carbon dioxide and humidity detection, thus realizing efficient gas and humidity detection functions.
Smart Images
Figure CN121109989A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of two-dimensional materials technology, and in particular to a method for preparing a large-area vanadium disulfide thin film, a photodetector, and its applications. Background Technology
[0002] Since the discovery of graphene in 2004, two-dimensional materials have attracted widespread attention from researchers due to their outstanding mechanical, optical, electrical, and catalytic properties. Unlike the single-atom-layer structure of graphene, transition metal chalcogenides, as a new class of two-dimensional materials, have a single-layer film consisting of a transition metal atom layer sandwiched between two chalcogenide atom layers, forming a "sandwich"-like structure. Due to their atomically flat surface, suitable band gap width, and excellent mechanical properties, transition metal chalcogenides can be applied to many advanced electronic devices such as field-effect transistors, memory, and various detectors.
[0003] Vanadium disulfide (VDS) is a member of the group VB transition metal chalcogenides. Bulk VDS is a narrow-bandgap semiconductor with a bandgap of 0.6 eV, while monolayer VDS exhibits bandgap-free half-metal properties. Phonon dispersion calculations show that VDS films undergo various stable structural phase transitions, including a tetragonal 1T phase, a hexagonal 2H phase, and a rhombohedral 3R phase, each exhibiting unique electronic properties. The 1T phase of VDS possesses ultra-high electrical conductivity, excellent electrocatalytic activity, and room-temperature ferromagnetism, while the 2H phase exhibits semiconductor properties and a larger magnetic moment, creating more opportunities for the development of electronic and spintronic devices. However, the thermodynamic instability of VDS and the tendency to form polymorphs during growth severely hinder the preparation of high-quality, large-area films. Therefore, developing a reliable method for preparing large-area VDS films is of great significance for further expanding its application fields. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing high-quality, large-area vanadium disulfide thin films and to develop a photodetector with simple structure, low energy consumption, and excellent performance. The prepared continuous vanadium disulfide thin film exhibits good uniformity and cleanliness. Furthermore, the photodetector based on the vanadium disulfide thin film demonstrates higher responsivity, more stable periodic response, and richer functionality.
[0005] To achieve the above effects, the technical solution adopted by the present invention is as follows.
[0006] According to one aspect of the present invention, a method for preparing a large-area vanadium disulfide thin film is provided, the method comprising the following steps: Step 1, High-temperature annealing pretreatment: The sapphire substrate material is placed in a mixed atmosphere of argon and oxygen for high-temperature annealing treatment to obtain the pretreated substrate. Step 2, Low-pressure chemical vapor deposition: Using sulfur powder and vanadium pentoxide powder as precursors, low-pressure chemical vapor deposition is performed on the substrate after pretreatment in step 1, and the growth time is 15 min to 20 min to obtain a large-area vanadium disulfide thin film.
[0007] Based on the above technical solution, the sapphire substrate material in step 1 is an Al2O3(0001) wafer; The conditions for the high-temperature annealing treatment described in step 1 are as follows: In the mixed atmosphere of argon and oxygen, the flow rate of argon is 270 sccm to 300 sccm, and the flow rate of oxygen is 5 sccm to 10 sccm. The high-temperature annealing treatment is performed at a temperature of 900 ℃~1000 ℃; The high-temperature annealing process takes 3 to 4 hours.
[0008] Based on the above technical solution, the evaporation temperature of sulfur powder in step 2 is 180 ℃~200 ℃, and the evaporation temperature of vanadium pentoxide powder is 680 ℃~750 ℃. The temperature for low-pressure chemical vapor deposition on the substrate, as described in step 2, is maintained between 790 °C and 850 °C.
[0009] Based on the above technical solution, in step 2, during low-pressure chemical deposition, the sulfur powder and vanadium pentoxide are positioned 20 cm–30 cm and 5 cm–10 cm away from the pretreated substrate, respectively. The mass ratio of sulfur powder to vanadium pentoxide powder is 10:1 to 30:1. The low-pressure environment is maintained at 1 Torr–1.2 Torr. The carrier gas is argon at 180 sccm–210 sccm. The temperature of the sulfur powder is increased from 20 ℃–40 ℃ to 180 ℃–200 ℃, the temperature of the vanadium pentoxide powder is increased from 20 ℃–40 ℃ to 680 ℃–750 ℃, and the temperature of the sapphire substrate is increased from 20 ℃–40 ℃ to 790 ℃–850 ℃, with a heating time of 20 min–30 min for each. The large-area vanadium disulfide film has a single-layer or multi-layer structure.
[0010] According to a second aspect of the present invention, a vanadium disulfide photodetector with negative photoconductivity is provided, the vanadium disulfide photodetector comprising a substrate (1), a vanadium disulfide thin film (2), a source electrode (3) and a drain electrode (4); the source electrode (3) and the drain electrode (4) are located on the upper surface of the substrate (1); the vanadium disulfide thin film (2) is located on the upper surface of the central channel of the source electrode (3) and the drain electrode (4).
[0011] Based on the above technical solution, the material of the substrate (1) is a thermally oxidized silicon wafer.
[0012] Based on the above technical solution, the source electrode (3) and drain electrode (4) are made of either Cr / Au or Ti / Au, and have a thickness of 3 nm / 30 nm to 10 nm / 100 nm.
[0013] Based on the above technical solution, the vanadium disulfide thin film (2) has a thickness of 0.6 nm to 2.4 nm, and the effective area of the film located on the upper surface of the central channel of the source electrode (3) and the drain electrode (4) is 5000 μm. 2 ~15000 μm 2 .
[0014] According to a third aspect of the present invention, an application of a large-area vanadium disulfide thin film in photoelectric detection is provided.
[0015] According to a fourth aspect of the present invention, an application of a vanadium disulfide photodetector in the detection of carbon dioxide and humidity is provided.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method for preparing large-area vanadium disulfide thin films provided by this invention adjusts the source concentration above the substrate by controlling the position of the precursor, ensuring that the substrate remains in a sulfur-rich state throughout the growth process. The use of a three-channel carrier gas delivery system and a low-pressure environment facilitates stable gas flow within the quartz tube. The absence of hydrogen and halide salts as auxiliary agents ensures safety and cleanliness throughout the experimental process. Characterization analysis confirms that the large-area vanadium disulfide thin films grown on sapphire substrates possess excellent quality.
[0017] (2) The vanadium disulfide photodetector prepared in this invention can achieve a source-drain current at the milliampere level when a working voltage of 1 V is applied across the source and drain electrodes; and the positive and negative photoconductive effects can be controllably adjusted through carbon dioxide gas adsorption and photoinduced desorption, exhibiting a large negative photoconductive responsivity (R0). λ =2680 A / W) and a stable periodic positive photoconductivity response; in addition, its sensitivity to carbon dioxide and moisture makes this photodetector applicable to both carbon dioxide gas detection and humidity detection. Attached Figure Description
[0018] Figure 1These are comparative images of blank sapphire substrates and vanadium disulfide films on sapphire substrates after growth, from Examples 1 and 2 of the present invention (left: blank sapphire substrate, middle: sapphire substrate with a single layer of vanadium disulfide film, right: sapphire substrate with multiple layers of vanadium disulfide film). Figure 2 These are atomic force microscopy images and height profile images of the vanadium disulfide thin film on the sapphire substrate described in Test Example 1 of this invention. Figure 3 This is the energy dispersive X-ray spectrum of the vanadium and sulfur elemental distribution of the vanadium disulfide thin film described in Test Example 1 of the present invention; Figure 4 This is a schematic diagram of the vanadium disulfide photodetector structure provided in Embodiment 3 of the present invention (wherein, 1 is the substrate, 2 is the vanadium disulfide thin film, 3 is the source electrode, and 4 is the drain electrode). Figure 5 The test results are for the negative photoconductivity response of the vanadium disulfide photodetector described in Test Example 2 of this invention. Figure 6 The test results are for the stable periodic positive photoconductivity effect of the vanadium disulfide photodetector described in Test Example 3 of the present invention. Figure 7 This is a test example of the source leakage current change of the vanadium disulfide photodetector described in Example 4 of the present invention under carbon dioxide gas and humidity detection. Detailed Implementation
[0019] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.
[0020] Unless otherwise specified, all raw materials used in this invention are obtained through purchase. The sapphire substrate (Al2O3(0001) wafer) was purchased from Wuhan Jingxin Optoelectronics Co., Ltd., and the sulfur powder (99.5% purity) and vanadium pentoxide powder (99.5% purity) were purchased from Alfaesa (China) Chemical Co., Ltd. and Anhui Zesheng Technology Co., Ltd., respectively. The Cr / Au metal heterojunction material (3 nm / 30 nm) was purchased from Huizhou Xinwenxiong Trading Co., Ltd.
[0021] The formulas for calculating the responsivity, external quantum efficiency, and detectivity of the photodetector in the embodiments are as follows: Response R λ = I ph / PS, where I ph Indicates the generated photocurrent (I ph =|I light -I dark |,I light I is the current under illumination. dark(where P is the current under dark conditions, S is the optical power density of the incident light, and S is the effective area of the thin film in the device under illumination.) External quantum efficiency EQE = hcR λ / eλ, where the parameters h, c, e and λ are Planck's constant, the speed of light, the elementary electron charge and the wavelength of the incident light, respectively; Detection rate D * = R λ S 1 / 2 / (2eI dark ) 1 / 2 .
[0022] Example 1 A method for preparing a large-area monolayer vanadium disulfide thin film includes the following steps: Step 1, High-temperature annealing pretreatment: A sapphire substrate (Al2O3(0001) wafer) with a side length of 1 cm × 1 cm is placed in a mixed atmosphere of 300 sccm of high-purity argon and 10 sccm of high-purity oxygen, that is, at a pressure of 1 Torr, the sapphire substrate is heated from 30 ℃ to 1000 ℃ in 30 min and held at that temperature for 4 hours to perform high-temperature annealing treatment, and the pretreated substrate is obtained.
[0023] Step 2, Low-Pressure Chemical Vapor Deposition (LPCVD): Using 2 g of sulfur powder and 100 mg of vanadium pentoxide powder as precursors, a large-area monolayer vanadium disulfide film was grown on the pretreated substrate described in Step 1 using LCVD. The sulfur powder temperature was increased from 30 °C to 200 °C, the vanadium pentoxide powder temperature from 30 °C to 750 °C, and the pretreated substrate temperature from 30 °C to 850 °C, with each temperature increase taking 30 min. Before growth, the sulfur powder and vanadium pentoxide powder were positioned 30 cm and 10 cm away from the pretreated substrate, respectively. During growth, 210 sccm of high-purity argon gas was introduced to maintain a vacuum pressure of 1.2 Torr in the chamber. The growth time was 16 min. After growth, the sample was allowed to cool naturally to room temperature in the furnace, resulting in a large-area monolayer vanadium disulfide film. A physical image of the large-area monolayer vanadium disulfide film is shown below. Figure 1 As shown, the left image is a blank sapphire substrate, and the middle image is a large-area monolayer vanadium disulfide thin film grown on the sapphire substrate.
[0024] Example 2 A method for preparing a large-area multilayer vanadium disulfide thin film includes the following steps: Step 1, High-temperature annealing pretreatment: A sapphire substrate (Al2O3(0001) wafer) with a side length of 1 cm × 1 cm was placed in a mixed atmosphere of 300 sccm of high-purity argon and 10 sccm of high-purity oxygen, that is, at a pressure of 1 Torr, the sapphire substrate was heated from 30 ℃ to 1000 ℃ in 30 min and held at that temperature for 4 hours to perform high-temperature annealing treatment, and the pretreated substrate was obtained.
[0025] Step 2, Low-Pressure Chemical Vapor Deposition (LPCVD): Using 3 g of sulfur powder and 100 mg of vanadium pentoxide powder as precursors, a large-area multilayer vanadium disulfide film was grown on the pretreated substrate described in Step 1 using LCVD. The sulfur powder temperature was increased from 30 °C to 200 °C, the vanadium pentoxide powder temperature from 30 °C to 750 °C, and the pretreated substrate temperature from 30 °C to 800 °C, with each temperature increase taking 30 min. Before growth, the sulfur powder and vanadium pentoxide powder were positioned 25 cm and 5 cm away from the pretreated substrate, respectively. During growth, 180 sccm of high-purity argon gas was introduced to maintain a vacuum pressure of 1.2 Torr in the chamber. The growth time was 18 min. After growth, the sample was allowed to cool naturally to room temperature in the furnace, resulting in a large-area multilayer vanadium disulfide film. A physical image of the large-area multilayer vanadium disulfide film is shown below. Figure 1 As shown, the left image is a blank sapphire substrate, and the right image is a large-area multilayer vanadium disulfide thin film grown on the sapphire substrate.
[0026] Test Example 1 Atomic force microscopy images of the large-area vanadium disulfide thin film prepared in Example 2 are provided by Figure 2 As shown, by measuring the height profile between the film and the substrate at the scratch, the thickness of the vanadium disulfide film is clearly visible to be approximately 2.097 nm; the elemental distribution images of vanadium and sulfur in the large-area vanadium disulfide film are shown below. Figure 3 As shown, its uniform distribution demonstrates the high-quality properties of the thin film.
[0027] Example 3 A vanadium disulfide photodetector with negative photoconductivity includes a substrate (1), a vanadium disulfide thin film (2), a source electrode (3), and a drain electrode (4). The source electrode (3) and drain electrode (4) are located on the upper surface of the substrate (1). The vanadium disulfide thin film (2) is located on the upper surface of the central channel of the source electrode (3) and drain electrode (4). The vanadium disulfide thin film (2) is a large-area multilayer vanadium disulfide thin film prepared in Example 2. The thickness of the vanadium disulfide thin film (2) is 2.097 nm. The substrate (1) is made of thermally oxidized silicon wafer. The source electrode (3) and drain electrode (4) are both made of Cr / Au metal heterojunction. The thickness of the Cr / Au metal heterojunction material is 3 nm / 30 nm. The area of the vanadium disulfide thin film located on the upper surface of the central channel of the source electrode (3) and drain electrode (4) is 8135 μm. 2 A schematic diagram of the vanadium disulfide photodetector is shown below. Figure 4 As shown.
[0028] Test Example 2 The performance of the vanadium disulfide photodetector prepared in Example 3 was tested by applying a wavelength of 254 nm and a power density of 50 μW / cm² to the vanadium disulfide photodetector at a source-drain voltage of 0.5 V. 2 Under ultraviolet light, the carbon dioxide gas adsorbed on the thin film surface causes the device to produce a negative photoconductive effect, that is, under illumination, the source and leakage currents decrease, as shown in the test results. Figure 5 As shown, the current changes from 0.202 mA to 0.191 mA within 50 s. In the experiment, the measured I... ph P, S, λ and I dark They are 10.9 μA and 50 μW / cm, respectively. 2 8135 μm 2 The wavelengths are 254 nm and 0.221 mA. The device exhibits a negative photoconductivity responsivity of 2680 A / W and an external quantum efficiency of 1.3 × 10⁻⁶. 6 The detection rate is 2.87 × 10⁻⁶. 12 Jones.
[0029] Test Example 3 After carbon dioxide was completely desorbed from the vanadium disulfide film surface described in Test Example 2, the wavelength was 450 nm and the power density was 100 mW / cm². 2 Under the action of a laser with a switching interval of 10 s, the photodetector generates a stable periodic positive photoconductive response. Under illumination, the source-drain current increases, and under no-illumination conditions, the source-drain current decreases. The specific response results are as follows: Figure 6 As shown. In the experiment, I was measured. ph P, S, λ and I darkThey are 0.9 μA and 100 mW / cm, respectively. 2 8135 μm 2 The device exhibits a wavelength of 450 nm and a wavelength of 0.193 mA. Its positive photoconductive responsivity is 0.1106 A / W, external quantum efficiency is 30.47%, and detectivity is 1.27 × 10⁻⁶ A / W. 8 Jones.
[0030] Test Example 4 Irradiate with laser (wavelength 254 nm, power density 50 μW / cm²). 2 The vanadium disulfide photodetector described in Example 3, after complete desorption of surface carbon dioxide, was placed in a carbon dioxide environment, and the change in the detector's conductivity was observed. Laser irradiation (wavelength 254 nm, power density 50 μW / cm²) was then performed. 2 The vanadium disulfide photodetector described in Example 3, after complete desorption of surface carbon dioxide, was placed in a humid environment, and the change in detector conductivity was observed. The conductivity changes under carbon dioxide and humid environments are as follows: Figure 7 As shown, the results indicate that the detector current increases when placed in a carbon dioxide environment and decreases when placed in a humid environment.
[0031] The above description is merely a few embodiments of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the technical solution of the present invention using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for preparing a large-area vanadium disulfide film, characterized in that, The preparation method comprises the following steps: Step 1, high-temperature annealing pretreatment: the sapphire substrate material is placed in a mixed atmosphere of argon and oxygen for high-temperature annealing treatment to obtain a pretreated substrate; Step 2, low-pressure chemical vapor deposition: sulfur powder and vanadium pentoxide powder are used as precursors to perform low-pressure chemical vapor deposition on the pretreated substrate in step 1 for 15-20 min to obtain a large-area vanadium disulfide film.
2. The production method according to claim 1, characterized by, The sapphire substrate material in step 1 is an Al2O3(0001) wafer with a size of no more than 2 inches; The high-temperature annealing treatment in step 1 is performed under the following conditions: The flow rate of argon in the mixed atmosphere of argon and oxygen is 270-300 sccm, and the flow rate of oxygen is 5-10 sccm; The temperature of the high-temperature annealing treatment is 900-1000 °C; The time of the high-temperature annealing treatment is 3-4 h.
3. The production method according to claim 1, characterized by, The evaporation temperature of the sulfur powder in step 2 is 180-200 °C, and the evaporation temperature of the vanadium pentoxide powder is 680-750 °C; The temperature of the low-pressure chemical vapor deposition on the substrate in step 2 is maintained at 790-850 °C.
4. The method of claim 1, wherein, In the low-pressure chemical deposition in step 2, the sulfur powder and vanadium pentoxide are respectively located at a distance of 20-30 cm and 5-10 cm from the pretreated substrate, and the mass ratio of the sulfur powder to the vanadium pentoxide powder is 10:1-30:
1. The low-pressure environment is maintained at 1-1.2 Torr. The carrier gas is argon at a flow rate of 180-210 sccm. The temperature of the sulfur powder is increased from 20-40 °C to 180-200 °C, the temperature of the vanadium pentoxide powder is increased from 20-40 °C to 680-750 °C, and the temperature of the sapphire substrate is increased from 20-40 °C to 790-850 °C. The temperature increasing time is 20-30 min. The large-area vanadium disulfide film has a single-layer or multi-layer structure.
5. A vanadium disulfide photodetector having negative photoconductivity, characterized in that, The vanadium disulfide photoelectric detector comprises a substrate (1), a vanadium disulfide film (2), a source electrode (3) and a drain electrode (4). The source electrode (3) and the drain electrode (4) are located on the upper surface of the substrate (1), and the vanadium disulfide film (2) is located on the upper surface of the central channel of the source electrode (3) and the drain electrode (4). The vanadium disulfide film (2) is prepared by any one of the preparation methods in claims 1-4.
6. The vanadium disulfide photodetector of claim 5, wherein, The material of the substrate (1) is a thermal oxide silicon wafer.
7. The vanadium disulfide photodetector of claim 5, wherein, The material of the source electrode (3) and the drain electrode (4) is any one of Cr / Au and Ti / Au, and the thickness is 3 nm / 30 nm-10 nm / 100 nm.
8. The vanadium disulfide photodetector of claim 5, wherein, The thickness of the vanadium disulfide film (2) is 0.6 nm to 2.4 nm, and the effective area of the film on the upper surface of the central channel of the source electrode (3) and the drain electrode (4) is 5000 μm 2 to 15000 μm 2 .
9. The large-area vanadium disulfide film prepared by any one of the preparation methods in claims 1-4 is used in photoelectric detection.
10. The vanadium disulfide photoelectric detector in any one of claims 5-8 is used in carbon dioxide and humidity detection.