Bi2SeS2 thin film, and preparation method and application thereof

Abstract

The application discloses a Bi2SeS2 thin film and a preparation method and application thereof. Under the protection of inert gas, elemental Bi powder, elemental Se powder and elemental S powder are mixed and ball milled to obtain Bi2SeS2 compound powder, the powder is subjected to discharge plasma sintering treatment to obtain Bi2SeS2 compound target material, and the target material is prepared into the Bi2SeS2 thin film by using a magnetron sputtering technology. The Bi2SeS2 compound powder is sintered rapidly at a low temperature and with low energy consumption, the composition of the Bi2SeS2 compound target material is easy to control, and the composition of the thin film in the later stage is easy to regulate. Meanwhile, the Bi2SeS2 compound powder and the Bi2SeS2 compound target material are prepared in a short time and have high magnetron sputtering efficiency, so that the volatilization of the volatile elements S and Se in the preparation process of the Bi2SeS2 thin film can be effectively controlled, and the composition segregation is reduced. The application has simple process, low cost and good repeatability.

Description

Technical Field

[0001] This invention relates to the field of new energy materials technology, specifically to a Bi2SeS2 thin film, its preparation method, and its application. Background Technology

[0002] With the increasing scarcity of energy and the deterioration of the environment, there is an urgent need to address the pressing energy and environmental issues. Thermoelectric conversion technology is a technique that directly converts thermal energy into electrical energy by utilizing the transport and interaction of charge carriers and phonons within a solid through thermoelectric materials. It has important applications in fields such as thermoelectric refrigeration and thermoelectric power generation. The performance of thermoelectric materials is generally expressed by the dimensionless thermoelectric figure of merit ZT (ZT = S). 2 The thermoelectric material is evaluated using σT / κ, where S, σ, κ, and T represent the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature of the material, respectively. A good thermoelectric material requires a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity.

[0003] Bi₂SeS₂ sulfide materials have a similar crystal structure to the widely accepted Bi₂Te₃, but their constituent elements are more inexpensive and environmentally friendly, exhibiting excellent thermoelectric potential and representing a novel high-performance sulfide material. Through doping and microstructure manipulation, its thermoelectric figure of merit (ZT) can reach over 1.0, making it one of the best-performing thermoelectric materials among sulfide materials currently available. However, compared to high-performance thermoelectric materials such as PbTe, its thermal conductivity is relatively high, indicating significant room for performance improvement. Due to interface effects, quantum size effects, and quantum tunneling effects, low-dimensional materials exhibit excellent thermoelectric properties. In particular, the significantly enhanced interface scattering leads to a marked decrease in thermal conductivity, making dimensional reduction a crucial method for optimizing thermoelectric material performance. Two-dimensional thin films, as important low-dimensional materials, not only play a vital role in the regulation of thermal transport but also enable the fabrication of flexible devices for application in emerging electronic industries, thus demonstrating broad application prospects. However, current research mainly focuses on bulk Bi2SeS2 materials. Se and S are volatile elements in Bi2SeS2, which are difficult to control during the preparation of thin film materials, unlike the preparation of bulk materials. The composition is severely segregated, making it difficult to obtain Bi2SeS2 thin film materials. Therefore, there are currently no reports on the preparation and performance of Bi2SeS2 thin film materials.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a Bi2SeS2 thin film, its preparation method and application, in order to solve the problem of the difficulty in preparing existing Bi2SeS2 thin films.

[0006] A first aspect of the present invention provides a method for preparing a Bi2SeS2 thin film, comprising the steps of:

[0007] S1. Under inert gas protection, elemental Bi powder, elemental Se powder and elemental S powder are mixed and ball-milled to obtain Bi2SeS2 compound powder.

[0008] S2. The Bi2SeS2 compound powder is subjected to spark plasma sintering treatment to obtain a Bi2SeS2 compound target material.

[0009] S3. Using magnetron sputtering technology, the Bi2SeS2 compound target is sputtered and deposited on a substrate to prepare the Bi2SeS2 thin film on the substrate.

[0010] Optionally, in step S1, the inert gas is selected from nitrogen and argon.

[0011] Optionally, in step S1, the molar ratio of elemental Bi powder, elemental Se powder, and elemental S powder is 2:1.0-1.1:2-2.1.

[0012] Optionally, in step S1, the parameters of the ball milling process include: a ball milling speed of 400-600 r / min, a ball-to-material ratio of 20:1-60:1, and a ball milling time of 15-30 h.

[0013] Optionally, in step S2, the parameters of the discharge plasma sintering treatment include: sintering temperature of 450-650℃, sintering pressure of 20-30kN, sintering stress of 25-100MPa, and sintering holding time of 30-55min.

[0014] Optionally, in step S3, the parameters of the magnetron sputtering technology include: magnetron sputtering power of 20-30W, magnetron sputtering working gas pressure of 0-1Pa, magnetron sputtering time of 15-25min, substrate temperature of 400-600K, and in-situ annealing time of 20-40min.

[0015] In a second aspect, the present invention provides a Bi2SeS2 thin film, wherein the Bi2SeS2 thin film is prepared by the preparation method of the Bi2SeS2 thin film described above.

[0016] A third aspect of the present invention provides an application of the Bi2SeS2 thin film of the present invention as a thermoelectric material.

[0017] Beneficial Effects: This invention utilizes a three-step method—mechanical alloying, spark plasma sintering, and magnetron sputtering—to prepare Bi₂SeS₂ thin films. The Bi₂SeS₂ compound powder is synthesized by high-energy ball milling at room temperature without high-temperature heating. Furthermore, the Bi₂SeS₂ compound powder undergoes rapid sintering at low temperatures and with low energy consumption, making it easy to control the composition of the Bi₂SeS₂ compound target and facilitate subsequent film composition adjustment. Simultaneously, the short preparation time of the Bi₂SeS₂ compound powder and target, coupled with high magnetron sputtering efficiency, effectively controls the volatilization of volatile elements such as S and Se during the Bi₂SeS₂ thin film preparation process, reducing component segregation. This invention offers a simple, low-cost, and highly reproducible process. Attached Figure Description

[0018] Figure 1 The image shows the X-ray diffraction pattern of the Bi2SeS2 thin film obtained in Example 1.

[0019] Figure 2 The image shows the SEM surface morphology of the Bi2SeS2 film obtained in Example 1.

[0020] Figure 3 The image shows the X-ray diffraction pattern of the Bi2SeS2 thin film obtained in Example 2.

[0021] Figure 4 The image shows the SEM surface morphology of the Bi2SeS2 film obtained in Example 2. Detailed Implementation

[0022] This invention provides a Bi₂SeS₂ thin film, its preparation method, and its applications. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Because Se and S are volatile elements in Bi₂SeS₂, they are particularly difficult to control during the preparation of thin film materials, resulting in severe component segregation. Therefore, obtaining existing Bi₂SeS₂ thin films is challenging.

[0025] Based on this, the present invention uses a target material prepared by mechanical alloying and discharge plasma treatment to prepare a Bi2SeS2 thin film by magnetron sputtering.

[0026] Specifically, this embodiment of the invention provides a method for preparing a Bi2SeS2 thin film, comprising the following steps:

[0027] S1. Under inert gas protection, elemental Bi powder, elemental Se powder and elemental S powder are mixed and ball-milled to obtain Bi2SeS2 compound powder.

[0028] S2. The Bi2SeS2 compound powder is subjected to spark plasma sintering treatment to obtain a Bi2SeS2 compound target material.

[0029] S3. Using magnetron sputtering technology, the Bi2SeS2 compound target is sputtered and deposited on a substrate to prepare the Bi2SeS2 thin film on the substrate.

[0030] The advantages of the three-step method for preparing Bi₂SeS₂ thin films in this invention are as follows: Bi₂SeS₂ compound powder is synthesized by high-energy ball milling at room temperature without high-temperature heating. Furthermore, the Bi₂SeS₂ compound powder undergoes rapid sintering at a low temperature and with low energy consumption, making it easy to control the composition of the Bi₂SeS₂ compound target and facilitate subsequent film composition adjustment. Simultaneously, the preparation time for both the Bi₂SeS₂ compound powder and the Bi₂SeS₂ compound target is short, and the magnetron sputtering efficiency is high, effectively controlling the volatilization of volatile elements such as S and Se during the Bi₂SeS₂ thin film preparation process and reducing component segregation. In addition, the process in this invention is simple, low-cost, and has good reproducibility.

[0031] In one implementation, step S1 specifically includes:

[0032] S11. Weigh and mix elemental Bi powder, elemental Se powder, and elemental S powder (all with a purity > 99.99%) in a molar ratio of 2:1.0-1.1:2-2.1 (e.g., 2:1:2) to obtain a mixture.

[0033] S12. Using a high-energy ball mill, in a ball mill jar protected by an inert atmosphere, mechanical alloying is used to cause the grinding balls and the mixture to undergo a chemical reaction during high-speed ball milling to generate Bi2SeS2 compound powder.

[0034] In one embodiment, the inert gas is selected from nitrogen and argon.

[0035] In one embodiment, the parameters of the ball milling process include: a ball milling speed of 400-600 r / min, a ball-to-material ratio of 20:1-60:1, and a ball milling time of 15-30 h.

[0036] In one embodiment, step S2 specifically includes: placing the Bi2SeS2 compound powder into a graphite mold and sintering it at a certain sintering temperature using a spark plasma sintering device to obtain a Bi2SeS2 compound target material.

[0037] In one embodiment, the parameters of the discharge plasma sintering treatment include: sintering temperature of 450-650℃, sintering pressure of 20-30kN, sintering stress of 25-100MPa, and sintering holding time of 30-55min.

[0038] In one embodiment, in step S3, the parameters of the magnetron sputtering technology include: magnetron sputtering power of 20-30W, magnetron sputtering working gas pressure of 0-1Pa, magnetron sputtering time of 15-25min, substrate temperature of 400-600K, and in-situ annealing time of 20-40min.

[0039] This invention provides a Bi2SeS2 thin film, wherein the Bi2SeS2 thin film is prepared by the preparation method of Bi2SeS2 thin film described above in this invention.

[0040] This invention provides an application of the Bi2SeS2 thin film described above as a thermoelectric material.

[0041] The present invention will be further described below through specific embodiments.

[0042] Example 1

[0043] Elemental Bi, Se, and S powders were weighed in a molar ratio of 2:1:2, with each element having a purity greater than 99.99%. The powders were mixed in a ball mill jar, which was then evacuated and filled with nitrogen before being placed in a high-energy ball mill for grinding. The ball-to-material mass ratio was 20:1, the mill speed was 400 r / min, and the grinding time was 25 h, yielding Bi₂SeS₂ compound powder. This Bi₂SeS₂ compound powder was then loaded into a graphite mold and subjected to spark plasma sintering (SPSS) to obtain a Bi₂SeS₂ compound target. The SPSS sintering process was carried out at a temperature of 500 °C, a pressure of 25 kN, and a holding time of 40 min. The Bi2SeS2 compound target was mounted on the sputtering target site, and a Bi2SeS2 thin film was prepared on the substrate using magnetron sputtering technology. During the magnetron sputtering process, the magnetron sputtering power was 25W, the working gas pressure was 0.5Pa, the substrate temperature was 573K, the magnetron sputtering time was 20min, and the in-situ annealing time was 30min. Figure 1 The image shows the X-ray diffraction pattern of the Bi₂SeS₂ thin film obtained in Example 1. Figure 1 It can be seen that the target material obtained in Example 1 is a pure phase Bi2SeS2 compound target material, and the main crystalline phase of the obtained film is Bi2SeS2 film. The X-ray diffraction peak intensity of the film grains is slightly different due to different orientations. At the same time, the degree of crystallization and size of the film grains are different due to different preparation parameters, which does not affect the final phase. Figure 2 The image shows the SEM surface morphology of the Bi2SeS2 film obtained in Example 1.

[0044] Example 2

[0045] Elemental Bi, Se, and S powders were weighed in a molar ratio of 2:1:2, with each element having a purity greater than 99.99%. The powders were mixed in a ball mill jar, which was then evacuated and filled with nitrogen before being placed in a high-energy ball mill for grinding. The ball-to-material mass ratio was 20:1, the mill speed was 500 r / min, and the grinding time was 20 h, yielding Bi₂SeS₂ compound powder. This Bi₂SeS₂ compound powder was then loaded into a graphite mold and subjected to spark plasma sintering (SPSS) to obtain a Bi₂SeS₂ compound target. The SPSS sintering process was carried out at a temperature of 550 °C, a pressure of 25 kN, and a holding time of 35 min. The Bi2SeS2 compound target was mounted on the sputtering target site, and a Bi2SeS2 thin film was prepared on the substrate using magnetron sputtering technology. During the magnetron sputtering process, the magnetron sputtering power was 25W, the working gas pressure was 0.5Pa, the substrate temperature was 473K, the magnetron sputtering time was 20min, and the in-situ annealing time was 25min. Figure 3 The image shows the X-ray diffraction pattern of the Bi₂SeS₂ thin film obtained in Example 2. Figure 3 It can be seen that the target material obtained in Example 2 is a pure phase Bi2SeS2 compound target material, and the main crystalline phase of the obtained film is Bi2SeS2 film. The X-ray diffraction peak intensity of the film grains is slightly different due to different orientations. At the same time, the degree of crystallization and size of the film grains are different due to different preparation parameters, which does not affect the final phase. Figure 4 The image shows the SEM surface morphology of the Bi2SeS2 film obtained in Example 2.

[0046] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a Bi₂SeS₂ thin film, characterized in that, Including the following steps: Under room temperature and inert gas protection, elemental Bi powder, elemental Se powder and elemental S powder were mixed and ball-milled to obtain Bi2SeS2 compound powder. The Bi2SeS2 compound powder was subjected to spark plasma sintering to obtain a Bi2SeS2 compound target material. The Bi2SeS2 compound target was sputtered and deposited onto a substrate using magnetron sputtering technology to prepare the Bi2SeS2 thin film on the substrate. The sintering temperature of the discharge plasma sintering treatment is 450-650℃, and the sintering holding time is 30-55min.

2. The method for preparing Bi₂SeS₂ thin films according to claim 1, characterized in that, The inert gas is selected from nitrogen and argon.

3. The method for preparing Bi₂SeS₂ thin films according to claim 1, characterized in that, The molar ratio of elemental Bi powder, elemental Se powder and elemental S powder is 2:1.0-1.1:2-2.

1.

4. The method for preparing Bi₂SeS₂ thin films according to claim 1, characterized in that, The parameters for the ball milling process include: a ball milling speed of 400-600 r / min, a ball-to-material ratio of 20:1-60:1, and a ball milling time of 15-30 h.

5. The method for preparing Bi₂SeS₂ thin films according to claim 1, characterized in that, The parameters of the discharge plasma sintering treatment include: sintering pressure of 20-30 kN and sintering pressure of 25-100 MPa.

6. The method for preparing Bi₂SeS₂ thin films according to claim 1, characterized in that, The parameters of the magnetron sputtering technology include: magnetron sputtering power of 20-30W, magnetron sputtering working gas pressure of 0-1Pa, magnetron sputtering time of 15-25min, substrate temperature of 400-600K, and in-situ annealing time of 20-40min.

7. A Bi₂SeS₂ thin film, characterized in that, The Bi2SeS2 thin film is prepared by the preparation method of Bi2SeS2 thin film according to any one of claims 1-6.

8. The application of the Bi2SeS2 thin film according to claim 7 as a thermoelectric material.

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