CVD (Chemical Vapor Deposition) growth method of low-dimensional telluride doped single crystal Ag2Te1-xSex

Abstract

The invention provides a CVD (Chemical Vapor Deposition) growth method of low-dimensional telluride doped single crystal Ag2Te1-xSex. The method comprises the following steps: 1) preparing a precursor, namely growing polycrystal Ag2Te1-xSex from Ag powder, Te powder and Se powder in different proportions through a CVT (Chemical Vapor Transfer) method; (2) precursor treatment: grinding the polycrystalline Ag2Te1-xSex into powder; and 3) single crystal growth: taking the polycrystal Ag2Te1-xSex powder as a reaction source, and generating single crystal Ag2Te1-xSex through a CVD (chemical vapor deposition) growth method (namely, a chemical vapor deposition method). By means of CVD growth and doping, appropriate doping elements are introduced into the low-dimensional telluride, lattice defects are controlled, and then the thermoelectric performance of the low-dimensional telluride is optimized; the single crystal Ag2Te1-xSex nanosheet obtained by the method has the characteristics of large size, high quality and the like, the surface flatness is high, lattice defects are few, and the application potential of the single crystal Ag2Te1-xSex nanosheet in electronic devices can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of two-dimensional material preparation, and in particular to a low-dimensional telluride-doped single crystal Ag2Te 1-x Se x CVD growth method. Background Art

[0002] The electron mobility and carrier concentration of low-dimensional telluride materials are important factors affecting their performance. In the prior art, Ag2Te is generally prepared by thermal evaporation. 1-x Se x However, due to the high diffusivity of silver ions during the preparation process, it is difficult to accurately control the structure and composition of the film by thermal evaporation, resulting in uneven film composition and affecting the stability and consistency of material properties. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above problems and provide a material Ag2Te that can optimize its thermoelectric performance by introducing appropriate doping elements into low-dimensional telluride and controlling lattice defects. 1-x Se x Preparation method.

[0004] To achieve the above object, the present invention proposes a low-dimensional telluride-doped single crystal Ag2Te 1-x Se x The CVD growth method comprises the following steps:

[0005] (1) Precursor preparation: Ag powder, Te powder and Se powder in different proportions are grown into polycrystalline Ag2Te by chemical vapor transport (CVT) method. 1-x Se x ;

[0006] (2) Precursor treatment: The polycrystalline Ag2Te 1-x Se x Grind into powder;

[0007] (3) Single crystal growth: Polycrystalline Ag2Te 1-x Se x The powder is used as a reaction source to generate single crystal Ag2Te by CVD growth method (ie chemical vapor deposition method). 1-x Se x .

[0008] Furthermore, the polycrystalline Ag2Te 1-x Se x In the powder, the mixing ratio is: Ag accounts for two-thirds of the molar ratio, Te and Se account for the remaining one-third, wherein the molar ratio of Se to Te is 0-20%.

[0009] Furthermore, step S3 is specifically as follows: polycrystalline Ag2Te 1-x Se x The powder was used as a reaction source and placed in the high temperature zone of a CVD reactor. Under the conditions of a reaction source temperature of 1040-1070°C and a growth zone temperature of 540-560°C, sapphire was used as a substrate, argon was introduced as a protective gas, and CVD growth was performed in a gas pressure range of 15-50 Torr for 360-480 minutes to obtain single crystal Ag2Te 1-x Se x .

[0010] Furthermore, the reaction source temperature is 1050° C.; the growth zone temperature is 550° C.; and the argon gas flow rate is 15 standard cubic centimeters per minute.

[0011] Furthermore, the gas pressure of the CVD reactor is adjusted and stabilized at 15 Torr by an oil pump exhaust valve; and the growth time of the CVD growth is 6 hours.

[0012] Furthermore, in the chemical vapor transport method, the temperature of the high temperature zone is 1050° C., the temperature of the low temperature zone is 950° C., and the reaction time is 3 weeks.

[0013] Furthermore, the sapphire substrate is located downstream of the low-temperature zone of the CVD reactor, and is 13 cm away from the high-temperature zone.

[0014] Furthermore, before the CVD growth reaction, the air in the quartz tube in the reaction furnace was removed by three purge processes of evacuating the pressure to below 50 mTorr and then filling with argon.

[0015] Furthermore, the single crystal Ag2Te 1-x Se x It has a nanosheet structure with uniform chemical composition distribution and optimized electron mobility, and is suitable for field-effect transistors or photodetector devices.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] 1. The present invention can introduce appropriate doping elements into low-dimensional telluride through doping technology and defect engineering during CVD growth, control lattice defects, and thus optimize its thermoelectric properties; by combining CVD method with doping and other means, the electronic transport properties of the material are improved, solving the traditional thermal evaporation method for preparing single crystal Ag2Te 1-x Se x The high diffusivity of silver ions causes uneven composition, which affects the stability of material performance.

[0018] 2. The present invention effectively suppresses the disordered diffusion of silver ions and achieves precise control of material composition through the combination of selenium Se doping technology and the temperature gradient during CVD growth.

[0019] 3. The present invention pre-synthesizes polycrystalline precursors through chemical vapor transport (CVT) to ensure the chemical homogeneity of the precursors and provide high-quality raw materials for subsequent single crystal growth.

[0020] 4. Single crystal Ag2Te obtained by the method of the present invention 1-x Se x Nanosheets have the characteristics of large size and high quality. Their surface flatness is high and there are few lattice defects. They can effectively improve their application potential in electronic devices (such as field-effect transistors, photodetectors, etc.). Their large size and high stability significantly improve the efficiency and life of the devices.

[0021] 5. The process of the present invention is highly controllable and suitable for large-scale production. During the process, three vacuum pumping and argon purge processes are used to ensure that the reaction environment is oxygen-free, reduce impurity interference, and the parameters are highly controllable. The operation repeatability is high, and large-scale preparation is easy to achieve.

[0022] 6. This invention fills the technical gap of precise preparation of low-dimensional telluride single crystals through the synergistic process of CVD and CVT, and solves the contradiction between composition control and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 CVT growth of polycrystalline Ag2Te in the embodiment of the present invention 1-x Se x Schematic diagram of the experimental setup;

[0024] Figure 2 The CVD-grown single crystal Ag2Te in the embodiment of the present invention 1-x Se x Schematic diagram of the experimental setup;

[0025] Figure 3 The single crystal Ag2Te obtained in the embodiment of the present invention 1-x Se x Optical microscope images of

[0026] Figure 4 The single crystal Ag2Te obtained in the embodiment of the present invention 1-x Se x AFM images of

[0027] Figure 5 The single crystal Ag2Te obtained in the embodiment of the present invention 1-x Se x EDS test results.

[0028] 1-Mixed powder of silver powder, tellurium powder and selenium powder; 2-Polycrystalline Ag2Te 1-x Se x Compound; 3-CVT high-temperature zone heating furnace; 4-CVT low-temperature zone heating furnace; 5-glass stopper; 6-gas inlet; 7-gas outlet; 8-polycrystalline Ag2Te 1-x Se x powder; 9-sapphire substrate; 10-CVD high temperature zone heating furnace; 11-CVD low temperature zone heating furnace. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be further described below.

[0030] This embodiment proposes a low-dimensional telluride-doped single crystal Ag2Te 1-x Se x The CVD growth method comprises the following steps:

[0031] (1) Precursor preparation: Ag powder, Te powder and Se powder in different proportions are grown into polycrystalline Ag2Te by chemical vapor transport (CVT) method. 1-x Se x ;

[0032] like Figure 1 The CVT reaction device shown in the figure has a quartz tube embedded in a horizontal reactor 1. A CVT high-temperature zone heating furnace 3 is provided near the left end of the quartz tube. The quartz tube cavity of the CVT high-temperature zone heating furnace 3 is used to place a mixed powder 1 of silver powder, tellurium powder and selenium powder. At the same time, a CVT low-temperature zone heating furnace 4 is provided at a distance to the right of the CVT high-temperature zone heating furnace 3. The quartz tube cavity of the CVT low-temperature zone heating furnace 4 is used to accommodate the generated polycrystalline Ag2Te 1-x Se x Compound, a glass plug 5 is sealed in the quartz tube on the right side of the CVT low temperature zone heating furnace 4.

[0033] In this embodiment, a mixed powder 1 formed by mixing high-purity silver powder (Ag powder), tellurium powder (Te powder) and selenium powder (Se powder) in a molar ratio of 2:0.95:0.05 is placed in a quartz tube at high temperature, sealed with a glass stopper 5 at high temperature, and then placed in a dual-temperature zone furnace for melting. The high-temperature end temperature formed by the CVT high-temperature zone heating furnace 3 is 1050°C, and the low-temperature end temperature formed by the CVT low-temperature zone heating furnace 4 is 950°C. After three weeks, large droplet-shaped polycrystalline Ag2Te 1-x Se x Compound 2.

[0034] (2) Precursor treatment: The polycrystalline Ag2Te obtained in step (1)1-x Se x Compound 2 was ground into powder to obtain polycrystalline Ag2Te 1-x Se x powder.

[0035] (3) Single crystal growth: Polycrystalline Ag2Te 1-x Se x The powder is used as a reaction source to generate single crystal Ag2Te by CVD growth method (ie chemical vapor deposition method). 1-x Se x .

[0036] like Figure 2 The CVD reaction device shown in the figure has a gas inlet 6 and a gas outlet 7 at both ends of the horizontal reactor II, a CVD high temperature zone heating furnace 10 is provided near the gas inlet 6, and a CVD low temperature zone heating furnace 11 is provided near the gas outlet 7. 1-x Se x The powder is placed in the high temperature zone formed by the CVD high temperature zone heating furnace 10 in the horizontal reactor II as a CVD reaction source, and the reaction substrate sapphire sheet (sapphire base) 9 is placed in the downstream position of the low temperature zone formed by the CVD low temperature zone heating furnace 11 in the horizontal reactor II. The temperature of this zone is the single crystal Ag2Te 1-x Se x The center distance between the high temperature zone and the low temperature zone in the horizontal reactor II is 13 cm.

[0037] In this embodiment, single crystal Ag2Te 1-x Se x Before growth, the quartz tube embedded in horizontal reactor II was sealed. Once sealed, it was first evacuated to below 50 mTorr using an oil pump. Then, the flow meter was switched to purge mode and argon (Ar) was introduced. This was continued for 1 minute, followed by shutting off the flow meter. The evacuation and refilling process was repeated three times to complete the purge process. This operation was intended to expel all air from the quartz tube. During growth, the temperature in the center of the high-temperature zone within reactor II was 1050°C, while the temperature at the sapphire substrate in the downstream low-temperature zone was 550°C. Argon was used as the shielding gas, with an inlet flow rate of 15 standard cubic centimeters per minute (sccm). The oil pump valve was adjusted to maintain the pressure in the quartz tube at 15 Torr. Growth was continued for 6 hours. After cooling naturally, high-quality Ag2Te3 was synthesized on an alumina substrate (sapphire substrate 9). 1-x Se x Single crystal nanosheets.

[0038] Figure 3 For the Ag2Te 1-x Se x Optical microscope image of a single-crystal nanosheet, from Figure 3 It can be seen that the size of the grown sample is about 10um; Figure 4 For the Ag2Te 1-x Se x AFM images of single-crystal nanosheets, from Figure 4 It can be seen that the thickness of the grown sample is about 35nm; Figure 5 For the Ag2Te 1-x Se x EDS test results of single crystal nanosheets, from Figure 5 It can be seen that the Se element accounts for 9.88%; the doping of selenium Se element is successfully achieved through the method of this embodiment, which effectively inhibits the disordered diffusion of silver ions and realizes the precise control of material composition. The Ag2Te prepared by the method of this embodiment 1-x Se x Single-crystal nanosheets have the characteristics of large size and high quality. Their surface flatness is high and there are few lattice defects, which can effectively improve their application potential in electronic devices (such as field-effect transistors, photodetectors, etc.).

[0039] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. A low-dimensional telluride-doped single crystal Ag2Te 1-x Se x The CVD growth method is characterized in that The steps include: (1) Precursor preparation: Ag powder, Te powder and Se powder in different proportions are grown into polycrystalline Ag2Te by chemical vapor transport method. 1-x Se x ; (2) Precursor treatment: The polycrystalline Ag2Te 1-x Se x Grind into powder; (3) Single crystal growth: Polycrystalline Ag2Te 1-x Se x The powder is used as a reaction source to generate single crystal Ag2Te by CVD growth method. 1- x Se x .

2. The low-dimensional telluride-doped single crystal Ag2Te according to claim 1 1-x Se x The CVD growth method is characterized in that The polycrystalline Ag2Te 1-x Se x In the powder, the molar ratio of Se to Te is 0 to 20%.

3. The low-dimensional telluride-doped single crystal Ag2Te according to claim 1 1-x Se x The CVD growth method is characterized in that Step S3 is specifically: polycrystalline Ag2Te 1-x Se x The powder was used as a reaction source and placed in the high temperature zone of a CVD reactor. Under the conditions of a reaction source temperature of 1040-1070°C and a growth zone temperature of 540-560°C, sapphire was used as a substrate, argon was introduced as a protective gas, and CVD growth was performed in a gas pressure range of 15-50 Torr for 360-480 minutes to obtain single crystal Ag2Te 1-x Se x .

4. The low-dimensional telluride-doped single crystal Ag2Te according to claim 3 1-x Se x The CVD growth method is characterized in that The reaction source temperature was 1050° C.; the growth zone temperature was 550° C.; and the argon flow rate was 15 standard cubic centimeters per minute.

5. The low-dimensional telluride-doped single crystal Ag2Te according to claim 3 1-x Se x The CVD growth method is characterized in that The gas pressure of the CVD reactor was adjusted by an oil pump exhaust valve and stabilized at 15 Torr; the growth time of the CVD growth was 6 hours.

6. The low-dimensional telluride-doped single crystal Ag2Te according to claim 1 1-x Se x The CVD growth method is characterized in that In the chemical vapor transport method, the temperature of the high temperature zone is 1050° C., the temperature of the low temperature zone is 950° C., and the reaction time is 3 weeks.

7. The low-dimensional telluride-doped single crystal Ag2Te according to claim 3 1-x Se x The CVD growth method is characterized in that The sapphire substrate is located downstream of the low-temperature zone of the CVD reactor, and is 13 cm away from the high-temperature zone.

8. The low-dimensional telluride-doped single crystal Ag2Te according to claim 1 1-x Se x The CVD growth method is characterized in that Before the CVD growth reaction, the air in the quartz tube in the reaction furnace was removed by three evacuation processes to below 50 mTorr and then filling with argon gas.

9. The low-dimensional telluride-doped single crystal Ag2Te according to claim 1 1-x Se x The CVD growth method is characterized in that The single crystal Ag2Te 1-x Se x It has a nanosheet structure with uniform chemical composition distribution and optimized electron mobility, and is suitable for field-effect transistors or photodetector devices.

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