Tin-doped molybdenum oxide nanofilms, their preparation methods, and near-infrared photodetectors

Abstract

This invention discloses a tin-doped molybdenum oxide nanofilm, its preparation method, and a near-infrared photodetector. The preparation method includes preparing the molybdenum oxide nanofilm using chemical vapor deposition; mixing stannous salt and a reducing agent in a hydrochloric acid solution to prepare an intercalation solution; and then dropping the intercalation solution onto the molybdenum oxide nanofilm for intercalation treatment at 50–70°C. The above preparation method is simple to operate. The use of tin intercalation in molybdenum oxide reduces the band gap of molybdenum oxide, achieving efficient absorption of near-infrared photons. The resulting tin-doped molybdenum oxide nanofilm has a large volume, uniform thickness, and good thermal stability, making it suitable for fabricating near-infrared photodetectors.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic materials technology, and in particular to a tin-doped molybdenum oxide nanofilm, its preparation method, and a near-infrared photodetector. Background Technology

[0002] Near-infrared photodetectors are devices that convert invisible infrared radiation signals into electrical signals and collect them. Infrared detection and imaging devices based on traditional narrow-bandgap inorganic semiconductor materials are expensive to produce and have complex processes, thus limiting their widespread application.

[0003] Layered α-molybdenum oxide, as a wide-bandgap semiconductor material, plays an important role and has many applications in optoelectronic devices. Its intrinsic wide-bandgap structure limits its spectral range to the ultraviolet band, but research has shown that ion doping can broaden its spectral response range, improve the performance of the semiconductor material, and maintain the integrity of the film surface. However, current methods for preparing ion-doped molybdenum oxide films are complex and it is difficult to prepare large-area, uniformly doped molybdenum oxide films. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a tin-doped molybdenum oxide nanofilm, its preparation method, and a near-infrared photodetector.

[0005] In a first aspect, the present invention provides a method for preparing tin-doped molybdenum oxide nanofilms, comprising the following steps:

[0006] S1. Molybdenum oxide nanofilms were prepared by chemical vapor deposition.

[0007] S2. Add stannous salt and reducing agent to hydrochloric acid solution, mix well, and obtain intercalation solution;

[0008] S3. The intercalation solution is coated onto the molybdenum oxide nanofilm, and the intercalation process is carried out at 50-70°C.

[0009] The order of steps S1 and S2 is not limited.

[0010] The method for preparing tin-doped molybdenum oxide nanofilms according to embodiments of the present invention has at least the following beneficial effects: the preparation method is simple to operate, wherein by using tin intercalation to molybdenum oxide, the band gap of molybdenum oxide can be reduced, thereby achieving absorption of near-infrared photons, and the prepared tin-doped molybdenum oxide nanofilm has a large volume and uniform thickness, and can be used to prepare near-infrared photodetectors.

[0011] According to some embodiments of the present invention, step S1 includes: placing molybdenum oxide powder and a substrate in a sealed environment, with the molybdenum oxide powder and the substrate spaced apart; raising the temperature in the sealed environment to 680–780°C under vacuum conditions, holding at that temperature for 2–4 hours, and then cooling to room temperature. Specifically, the molybdenum oxide powder can be placed in an open high-temperature resistant container, and then the open high-temperature resistant container can be placed in a CVD tube furnace; a high-temperature resistant substrate can be placed upstream and / or downstream of the open high-temperature resistant container in the CVD tube furnace; raising the temperature in the CVD tube furnace to 680–780°C under vacuum conditions, holding at that temperature for 2–4 hours, and then cooling to room temperature. Specifically, the high-temperature resistant substrate can be placed 10–15 cm away from the open high-temperature resistant container. The open high-temperature resistant container can be a quartz cup, a ceramic boat, a crucible, etc.; the high-temperature resistant substrate can be a silicon dioxide substrate, a silicon substrate, or other high-temperature resistant substrates. Before placing the high-temperature resistant substrate into the CVD tube furnace, it is generally cleaned first. Specifically, it can be cleaned three times in sequence with alcohol, acetone, and deionized water, and then dried with a nitrogen gun.

[0012] According to some embodiments of the present invention, in step S1, the temperature in the sealed environment is increased to 680-780°C at a rate of 10-20°C / min.

[0013] According to some embodiments of the present invention, in step S2, the stannous salt is selected from stannous chloride.

[0014] According to some embodiments of the present invention, in step S2, the reducing agent is selected from tartaric acid.

[0015] When preparing the intercalation solution, if the deionized aqueous solution of stannous salt (such as stannous chloride) is prepared directly, the stannous salt will dissolve directly in water and produce stannous hydroxide precipitate. Therefore, hydrochloric acid needs to be added to inhibit the reaction. Thus, a dilute hydrochloric acid solution of a certain concentration needs to be prepared in advance, and then the stannous salt and reducing agent are mixed with the dilute hydrochloric acid solution.

[0016] According to some embodiments of the present invention, in step S2, the concentration of the hydrochloric acid solution is 0.2 to 0.4 mol / L.

[0017] According to some embodiments of the present invention, step S3 includes: heating the molybdenum oxide nanofilm at 50-70°C, and then applying the intercalation solution onto the molybdenum oxide nanofilm for intercalation treatment. Specifically, the molybdenum oxide nanofilm can be placed on a heating stage at 50-70°C, with a glass slide placed between the molybdenum oxide nanofilm and the heating stage. The intercalation solution is applied to the molybdenum oxide nanofilm for intercalation treatment, and the color change of the molybdenum oxide nanofilm is observed. Specifically, it can be observed every three minutes under an optical microscope until the interface turns completely green, indicating that the treatment is complete.

[0018] In a second aspect, the present invention provides a tin-doped molybdenum oxide nanofilm, which is prepared by any of the tin-doped molybdenum oxide nanofilm preparation methods provided in the first aspect of the present invention.

[0019] A third aspect of the present invention provides a near-infrared photodetector, comprising:

[0020] Insulating substrate;

[0021] A metal electrode, comprising a positive electrode and a negative electrode, wherein the positive electrode and the negative electrode are disposed on the insulating substrate with a gap between them;

[0022] A graphene layer, which is overlapped on the positive electrode and the negative electrode;

[0023] A tin-doped molybdenum oxide nanofilm, wherein the tin-doped molybdenum oxide nanofilm is stacked on the graphene layer, and the tin-doped molybdenum oxide nanofilm is the tin-doped molybdenum oxide nanofilm provided in the second aspect of the present invention.

[0024] According to some embodiments of the present invention, the insulating substrate is made of at least one of single-crystal silicon, quartz glass, mica, SiO2, Al2O3, sapphire, and PET.

[0025] The electrodes can be made of gold. During fabrication, photolithography can be used to define the electrode area, and then thermal evaporation can be used to fabricate the electrodes. The thickness of the electrodes is generally 80–100 nm. The graphene layer can be a single layer or multiple layers. Attached Figure Description

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0027] Figure 1 This is a schematic diagram of the preparation of molybdenum oxide nanofilms by chemical vapor deposition in Example 1 of the present invention;

[0028] Figure 2 This is a scanning electron microscope image of the molybdenum oxide nanofilm prepared in Example 1 of the present invention;

[0029] Figure 3 This is the X-ray diffraction pattern of the molybdenum oxide nanofilm prepared in Example 1 of the present invention;

[0030] Figure 4 This is the Raman spectrum of the molybdenum oxide nanofilm prepared in Example 1 of this invention;

[0031] Figure 5 This is the X-ray diffraction pattern of the tin-doped molybdenum oxide nanofilm of Example 1 of the present invention;

[0032] Figure 6 This is a schematic diagram of the structure of an embodiment of the near-infrared photodetector of the present invention;

[0033] Figure 7 yes Figure 6 The fabrication flowchart of the near-infrared photodetector is shown below;

[0034] Figure 8 for Figure 6 The image shows the photocurrent of the near-infrared photodetector.

[0035] Figure reference numerals: 11-CVD tube furnace, 12-quartz jar, 13-silicon oxide substrate, 21-insulating substrate, 211-single crystal silicon substrate, 212-silicon dioxide layer, 22-electrode, 221-positive electrode, 222-negative electrode, 23-graphene layer, 24-tin-doped molybdenum oxide nanofilm. Detailed Implementation

[0036] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0037] Example 1

[0038] A tin-doped molybdenum oxide nanofilm, the preparation method of which includes the following steps:

[0039] S1. Preparation of molybdenum oxide nanofilms: Specifically as follows... Figure 1 As shown, a certain mass of molybdenum oxide powder was weighed and placed in a quartz jar 12, which was then placed in a CVD tube furnace 11. A silicon oxide substrate was taken, cleaned three times sequentially with alcohol, acetone, and deionized water, and then dried with a nitrogen gun. The silicon oxide substrate 13 was then placed in the CVD tube furnace 11 10 cm away from the quartz jar 12 containing the molybdenum oxide powder. Nitrogen gas was then purged into the CVD tube furnace 11 three times to remove air, and a vacuum treatment was performed. The temperature inside the CVD tube furnace 11 was increased to 680°C at a rate of 10°C / min, and held at that temperature for 4 hours. The furnace was then allowed to cool naturally to room temperature, producing a molybdenum oxide nanofilm on the silicon oxide substrate. The nanofilm was then peeled off from the silicon oxide substrate to obtain the molybdenum oxide nanofilm.

[0040] S2. Preparation of the intercalation solution, including: first, preparing 50 mL of 0.23 mol / L hydrochloric acid solution; then, adding appropriate amounts of stannous chloride powder and tartaric acid powder to the prepared hydrochloric acid solution, and gently stirring with a glass rod to obtain a clear and transparent intercalation solution.

[0041] S3. The molybdenum oxide nanofilm is subjected to tin intercalation treatment, including: heating the heating stage to 50-60°C, placing a glass slide on the heating stage, then placing the molybdenum oxide nanofilm obtained in step S1 on the glass slide, using a dropper to take the intercalation solution obtained in step S2 and drop it onto the molybdenum oxide nanofilm, and then observing the color change of the molybdenum oxide nanofilm. The observation is performed under an optical microscope every three minutes until the interface turns completely green. Then, heating is stopped, and the film is cooled to room temperature to obtain a tin-doped molybdenum oxide nanofilm.

[0042] The molybdenum oxide nanofilm prepared in step S1 of this embodiment was observed and detected using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy, respectively. The results are as follows: Figure 2 , Figure 3 and Figure 4 As shown. By Figure 2 Scanning electron microscopy images show that the prepared molybdenum oxide consists of large-sized plate-like crystals. Figure 3 The X-ray diffraction pattern shows strong diffraction peaks at 12.8°, 25.76°, and 39.04°, corresponding to the (020), (040), and (060) planes of α-MoO3 (JCPDS: 05-0508), respectively. Figure 4 Raman spectroscopy revealed two fingerprint phonon modes at 285 cm⁻¹ and 820 cm⁻¹, corresponding to the B₃g and Ag modes of MoO₃, respectively. X-ray diffraction was used to test the tin-doped molybdenum oxide nanofilm prepared in this embodiment, and the results are as follows. Figure 5 As shown, by Figure 5 It can be seen that the (040) peak shifts to the left in the figure. Calculations show that the interfacial spacing has increased, proving that the Sn atom has successfully inserted into the van der Waals interstices.

[0043] Example 2

[0044] A tin-doped molybdenum oxide nanofilm, the preparation method of which includes the following steps:

[0045] S1. Preparation of molybdenum oxide nanofilms: A certain amount of molybdenum oxide powder was weighed and placed in a quartz jar, which was then placed in a CVD tube furnace. A silicon substrate was taken and cleaned three times in sequence with alcohol, acetone, and deionized water, and then dried with a nitrogen gun. The silicon substrate was then placed in the CVD tube furnace at a distance of 12 cm from the quartz jar containing the molybdenum oxide powder. Nitrogen gas was then purged into the CVD tube furnace three times to remove air, and a vacuum treatment was performed. The temperature inside the CVD tube furnace was increased to 780℃ at a rate of 20℃ / min, and held at that temperature for 2 hours. The furnace was then allowed to cool naturally to room temperature, producing molybdenum oxide nanofilms on the silicon substrate. The nanofilms were then peeled off from the silicon substrate to obtain the molybdenum oxide nanofilms.

[0046] S2. Preparation of the intercalation solution, including: first, preparing 50 mL of 0.4 mol / L hydrochloric acid solution; then, adding appropriate amounts of stannous chloride powder and tartaric acid powder to the prepared hydrochloric acid solution, and gently stirring with a glass rod to obtain a clear and transparent intercalation solution.

[0047] S3. The molybdenum oxide nanofilm is subjected to tin intercalation treatment, including: heating the heating stage to 60-70°C, placing a glass slide on the heating stage, and then placing the molybdenum oxide nanofilm obtained in step S1 on the glass slide. The intercalation solution obtained in step S2 is dropped onto the molybdenum oxide nanofilm using a dropper. The color change of the molybdenum oxide nanofilm is then observed. The observation is performed under an optical microscope every three minutes until the interface turns completely green. Heating is then stopped, and the film is cooled to room temperature to obtain a tin-doped molybdenum oxide nanofilm.

[0048] Example 3

[0049] A tin-doped molybdenum oxide nanofilm, the preparation method of which includes the following steps:

[0050] S1. Preparation of molybdenum oxide nanofilms: A certain mass of molybdenum oxide powder was weighed and placed in a quartz jar, which was then placed in a CVD tube furnace. Two quartz glass substrates were taken and cleaned three times in sequence with alcohol, acetone, and deionized water, and then dried with a nitrogen gun. The two quartz glass substrates were placed upstream and downstream of the quartz jar (containing molybdenum oxide powder) in the CVD tube furnace, respectively, with a distance of 15 cm between each substrate and the jar. Nitrogen gas was then introduced into the CVD tube furnace three times to purge the air, and a vacuum treatment was performed. The temperature inside the CVD tube furnace was increased to 700℃ at a rate of 15℃ / min, and held at that temperature for 3 hours. The furnace was then allowed to cool naturally to room temperature, producing molybdenum oxide nanofilms on a silicon substrate. The nanofilms were then peeled off from the silicon substrate to obtain the molybdenum oxide nanofilms.

[0051] S2. Preparation of the intercalation solution, including: first, preparing 50 mL of 0.3 mol / L hydrochloric acid solution; then, adding appropriate amounts of stannous chloride powder and tartaric acid powder to the prepared hydrochloric acid solution, and gently stirring with a glass rod to obtain a clear and transparent intercalation solution.

[0052] S3. The molybdenum oxide nanofilm is subjected to tin intercalation treatment, including: heating the heating stage to 55-65°C, placing a glass slide on the heating stage, then placing the molybdenum oxide nanofilm obtained in step S1 on the glass slide, using a dropper to take the intercalation solution obtained in step S2 and drop it onto the molybdenum oxide nanofilm, and then observing the color change of the molybdenum oxide nanofilm. The observation is performed under an optical microscope every three minutes until the interface turns completely green. Then, the heating is stopped, and the film is cooled to room temperature to obtain a tin-doped molybdenum oxide nanofilm.

[0053] The tin-doped molybdenum oxide prepared above can be used to fabricate near-infrared photodetectors. For example, please refer to... Figure 6 , Figure 6 A schematic diagram of an embodiment of the near-infrared photodetector of the present invention is shown. Figure 6 As shown, the near-infrared photodetector includes an insulating substrate 21, a metal electrode 22, a graphene layer 23, and a tin-doped molybdenum oxide nanofilm 24.

[0054] The insulating substrate 21 can be made of at least one of monocrystalline silicon, quartz glass, mica, SiO2, Al2O3, sapphire, and PET. In this embodiment, the insulating substrate 21 includes a monocrystalline silicon substrate 211 and a silicon dioxide layer 212 disposed on the surface of the monocrystalline silicon substrate 211. The thickness of the silicon dioxide layer 212 is generally 250–350 nm. The metal electrode 22 includes a positive electrode 221 and a negative electrode 222, which are disposed on the side of the silicon dioxide layer 212 facing away from the monocrystalline silicon substrate 211. The metal electrode 22 can specifically be a gold electrode, and its thickness can be set to 80–100 nm. A graphene layer 23 is disposed on the positive electrode 221 and the negative electrode 222. The graphene layer 23 can be a single layer or multiple layers; in this embodiment, a single-layer graphene layer is used. Tin-doped molybdenum oxide nanofilm 24 is stacked on graphene layer 23. The tin-doped molybdenum oxide nanofilm 24 used in this embodiment is the tin-doped molybdenum oxide nanofilm prepared in Example 1.

[0055] Figure 6 The fabrication of the near-infrared photodetector shown can be referred to Figure 7 Specifically, it includes the following steps:

[0056] S1. Take a single-crystal silicon substrate 211, such as Figure 7 As shown in (a); and then as shown in (a). Figure 7 As shown in (b), an insulating substrate 21 is obtained by depositing a silicon dioxide layer 212 on a single-crystal silicon substrate;

[0057] S2. The gold electrode region is defined on the silicon dioxide layer 212 using photolithography, and then the gold electrode is fabricated using thermal evaporation. The gold electrode includes a positive electrode 221 and a negative electrode 222, as shown below. Figure 7 As shown in (c);

[0058] S3, such as Figure 7 As shown in (d), a graphene layer 23 is disposed on the gold electrode, and the graphene layer 23 overlaps the positive electrode 221 and the negative electrode 222.

[0059] S4, such as Figure 7 As shown in (e), a near-infrared photodetector is prepared by depositing a tin-doped molybdenum oxide nanofilm 24 on a graphene layer 23.

[0060] The above-prepared samples were subjected to 2200nm illumination. Figure 6 The near-infrared photodetector shown was used for photocurrent image testing, and the results are as follows: Figure 8 As shown, by Figure 8 It can be seen that the near-infrared photodetector exhibits a significant light response, with a rise time of 70s and a fall time of 30s.

[0061] The above near-infrared photodetector combines a graphene layer with a tin-doped molybdenum oxide nanofilm into a stacked structure via van der Waltz forces. By intercalating the tin into the molybdenum oxide, the bandgap of the molybdenum oxide can be reduced, thereby achieving efficient absorption of near-infrared photons. Photogenerated carriers are transferred to the graphene layer, and then the ultra-high mobility of graphene is used to transport the photogenerated carriers to the two end electrodes, thus achieving a high responsivity for near-infrared light.

Claims

1. A method for preparing tin-doped molybdenum oxide nanofilms, characterized in that, Includes the following steps: S1. Preparation of molybdenum oxide nanofilm, comprising: placing molybdenum oxide powder and substrate in a sealed environment, wherein the molybdenum oxide powder and substrate are placed at a distance of 10-15 cm, and under vacuum conditions, raising the temperature in the sealed environment to 680-780°C at a rate of 10-20°C / min, holding at the temperature for 2-4 hours, and then cooling to room temperature; S2. Add stannous salt and reducing agent to a hydrochloric acid solution with a concentration of 0.2~0.4 mol / L, mix well, and prepare an intercalation solution; the reducing agent is selected from tartaric acid; S3. The intercalation solution is coated onto the molybdenum oxide nanofilm, and the intercalation process is performed at 50~70°C, including: heating the molybdenum oxide nanofilm at 50~70°C, and then dropping the intercalation solution onto the molybdenum oxide nanofilm to perform the intercalation process, thereby obtaining a tin-doped molybdenum oxide nanofilm. The order of steps S1 and S2 is not limited.

2. The method for preparing tin-doped molybdenum oxide nanofilms according to claim 1, characterized in that, In step S2, the stannous salt is selected from stannous chloride.

3. A tin-doped molybdenum oxide nanofilm, characterized in that, The tin-doped molybdenum oxide nanofilm was prepared by the method described in any one of claims 1 to 2.

4. A near-infrared photodetector, characterized in that, include: Insulating substrate; A metal electrode, comprising a positive electrode and a negative electrode, wherein the positive electrode and the negative electrode are disposed on the insulating substrate with a gap between them; A graphene layer, which is overlapped on the positive electrode and the negative electrode; A tin-doped molybdenum oxide nanofilm, wherein the tin-doped molybdenum oxide nanofilm is disposed on the graphene layer, and the tin-doped molybdenum oxide nanofilm is the tin-doped molybdenum oxide nanofilm according to claim 3.

5. The near-infrared photodetector according to claim 4, characterized in that, The insulating substrate is made of at least one of the following materials: single crystal silicon, quartz glass, mica, SiO2, Al2O3, sapphire, and PET.

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