A method for preparing high power factor Bi2Se3 thin film based on post-tellurization treatment

Abstract

The present invention belongs to the technical field of thermoelectric thin film materials, and specifically discloses a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment, comprising the following steps: S1, preparing a target material; S2, placing a substrate and the target material; S3, adjusting the vacuum degree; S4, thin film deposition to obtain a Bi2Se3 thin film precursor; S5, post-tellurization treatment to obtain a Bi2Se3 thin film precursor. 3‑x Te y Thermoelectric film. The present invention adopts the above-mentioned preparation method of high power factor Bi2Se3 film based on post-tellurization treatment, which has simple preparation process and good repeatability. 3‑x Te y The room-temperature power factor of the thermoelectric film is as high as 20.74 μW·cm ‑1 K ‑1 , this film has broad application prospects in areas such as self-powered wearable devices.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric thin film materials, and in particular to a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment. Background Art

[0002] Thermoelectric materials are functional materials that can directly convert heat and electrical energy. Thermoelectric devices based on thermoelectric thin film materials have the advantages of being lightweight, highly integrated, and having a high output power density. They have broad application prospects in the fields of self-powered low-power electronic components such as wearable devices. The performance of thermoelectric materials is usually measured by the dimensionless thermoelectric figure of merit ZT, which is defined as ZT = (S 2 σ / κ)T. Where S is the Seebeck coefficient of the material, σ is the electrical conductivity of the material, κ is the thermal conductivity of the material, and T is the absolute temperature. 2 σ is called the power factor. A high power factor is of great significance for the large-scale promotion and application of thermoelectric power generation devices.

[0003] Bismuth telluride (Bi2Te3) is the only commercially available high-performance near-room-temperature thermoelectric material. However, tellurium (Te) is expensive, with reserves in the Earth's crust at only 0.001 ppm. Bismuth selenide (Bi2Se3), which has the same crystal structure and contains selenium (Se), is abundant and inexpensive in the Earth's crust. However, its inherently low electrical performance makes it unable to meet the demand for self-powered, massive, low-power electronic components in the Internet of Things era. Therefore, a thermoelectric thin-film material that maximizes the high performance of Bi2Te3 while reducing the Te content is urgently needed. This is of great significance for the development of low-cost, wearable thermoelectric thin-film power generation devices. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment, which has a simple preparation process and good repeatability. 3-x Te y The power factor of the thermoelectric film is as high as 20.74 μW·cm at room temperature. -1 K -1 , this film has broad application prospects in areas such as self-powered wearable devices.

[0005] To achieve the above object, the present invention provides a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment, comprising the following steps:

[0006] S1. Target preparation: Bi particles and Se particles are mixed uniformly according to a certain ratio, sealed in a tube, melted and sintered to obtain an ingot, which is crushed and pressed using a plasma discharge sintering technique to obtain a Bi2Se3 polycrystalline target;

[0007] S2. Place the substrate and target: Place the Bi2Se3 polycrystalline target obtained in S1 on the sputtering target position of the PLD system chamber. At the same time, fix the ultrasonically cleaned substrate in the center of the sample tray and adjust the distance between the substrate and the Bi2Se3 polycrystalline target to 5-10 cm.

[0008] S3. Adjust the vacuum degree: Pump the vacuum degree in the PLD system chamber to be equal to or less than 4×10 -4 After the pressure reaches 1500 Pa, high-purity argon gas is filled in, and the dynamic equilibrium pressure of the argon gas is kept stable by controlling the gas flow rate;

[0009] S4. Thin film deposition: adjusting the deposition temperature, laser energy density, and laser frequency to pre-sputter the Bi2Se3 polycrystalline target to obtain a Bi2Se3 polycrystalline target with surface impurities removed, then opening the substrate baffle to deposit a Bi2Se3 thin film precursor;

[0010] S5, post-tellurization treatment: according to the proportion, the Bi2Se3 film precursor obtained in S7 and Te particles are vacuum sealed, and then heated for 5-120min, and then taken out after cooling to obtain Bi2Se 3-x Te y Thermoelectric thin films.

[0011] Preferably, S1 comprises the following steps:

[0012] S11, mixing Bi particles and Se particles uniformly according to a certain proportion and placing them into a quartz tube for sealing;

[0013] S12, placing the sealed quartz tube into a muffle furnace for melting and sintering at a temperature of 800-1000° C. for 5-24 hours to obtain an ingot;

[0014] S13. The ingot is crushed and ground into powder, and then subjected to plasma discharge sintering at a sintering pressure of 10-50 MPa, a sintering temperature of 400-600° C., and a sintering time of 10-60 min, and pressed to obtain a Bi2Se3 polycrystalline target.

[0015] Preferably, in S2, the substrate is one of a single crystal Al2O3 substrate, an amorphous SiO2 substrate, a mica substrate, a high temperature resistant polyimide substrate, etc.

[0016] Preferably, in S3, the dynamic equilibrium pressure of the argon gas is 1-50 Pa.

[0017] Preferably, in S4, the deposition temperature is 200-450°C, and the laser energy density is 1.0-1.5 J / cm 2 , the laser frequency is 1-5Hz.

[0018] Preferably, in S5, the mass ratio of the Bi2Se3 thin film precursor to the Te particles is 1:50 - 500, and the purity of the Te particles is not less than 99.99%.

[0019] Preferably, in S5, the vacuum encapsulation treatment uses a quartz tube with a vacuum degree lower than 4×10 -3 Pa, and the heating uses a tube furnace or a box furnace, and the heating temperature is 250 - 450 °C.

[0020] Therefore, the present invention adopts the above-mentioned method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment, and the beneficial effects are as follows:

[0021] The preparation process of the present invention is simple and has good repeatability. The prepared Bi2Se 3-x Te y thermoelectric thin film has a power factor as high as 20.74 μW·cm -1 K -1 0] at room temperature, and this thin film has broad application prospects in the fields of self-powered wearable devices, etc.

[0022] The technical solution of the present invention will be further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flowchart of an embodiment of the method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to the present invention;

[0024] Figure 2 is an X-ray diffraction pattern of an embodiment of the method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to the present invention;

[0025] Figure 3 is a scanning electron microscope image of an embodiment of the method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to the present invention. Among them, (a) is the Bi2Se8] x thermoelectric thin film prepared with a tellurization time of 0 min, (b) is the Bi2Se x Te y (0 < x < 3, 0 < y < 2) thermoelectric thin film prepared with a tellurization time of 30 min, (c) is the Bi2Se x Te y (0 < x < 3, 0 < y < 2) thermoelectric thin film prepared with a tellurization time of 60 min, (d) is the Bi2Se x Te y (0 < x < 3, 0 < y < 2) thermoelectric thin film prepared with a tellurization time of 90 min, (e) is the Bi element distribution diagram, (f) is the Se element distribution diagram, and (g) is the Te element distribution diagram;

[0026] Figure 4 This is an atomic scale schematic diagram of an embodiment of a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to the present invention;

[0027] Figure 5 This is a graph showing the relationship between power factor and temperature in an embodiment of a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment of the present invention;

[0028] Figure 6 This is a graph showing the relationship between the Seebeck coefficient and temperature in an embodiment of a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment of the present invention;

[0029] Figure 7 This is a graph showing the relationship between conductivity and temperature in an embodiment of a method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0031] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0032] Example 1

[0033] A high power factor Bi2Se3 film based on post-tellurization treatment, such as Figure 1 As shown, its preparation method is as follows:

[0034] S1. Preparation of target material:

[0035] S11, Bi particles (99.999%) and Se particles (99.999%) were mixed evenly according to the molar ratio of Bi:Se=2:3, and the mixed Bi particles and Se particles were placed in a quartz tube, and the vacuum degree was drawn to 4×10 -3 After Pa, the tube is sealed;

[0036] S12, placing the sealed quartz tube in a muffle furnace and raising the temperature to 800° C. for 10 hours, maintaining the temperature for 10 hours, and cooling naturally to obtain an ingot;

[0037] S13. The melted ingot is crushed and ground into powder, and sintered and pressed using plasma discharge sintering technology at a sintering temperature of 500° C., a sintering pressure of 10 MPa, and a sintering time of 30 min to obtain a Bi2Se3 polycrystalline target.

[0038] S2. Place substrate and target:

[0039] The Bi2Se3 polycrystalline target obtained in S1 was placed at the sputtering target position of the PLD system chamber. At the same time, the single crystal Al2O3 substrate was glued to the center of the sample tray with silver glue. Before use, the single crystal Al2O3 substrate was ultrasonically cleaned three times in anhydrous ethanol and deionized water respectively, each time for 10 minutes. The distance between the single crystal Al2O3 substrate and the Bi2Se3 polycrystalline target was adjusted to 5 cm.

[0040] S3. Adjust the vacuum degree:

[0041] The vacuum degree in the PLD system chamber is reduced to 4×10 -4 After reaching 40 Pa, high-purity argon gas (99.999%) is filled in, and the dynamic equilibrium pressure of the argon gas is maintained at 40 Pa by controlling the gas flow rate.

[0042] S4. Thin film deposition:

[0043] Adjust the deposition temperature to 375°C and the laser energy density to 1.2 J / cm 2 , the laser frequency is 2 Hz, the Bi2Se3 polycrystalline target is pre-sputtered to remove the surface impurities of the Bi2Se3 polycrystalline target, the substrate baffle is opened after 5 minutes, the deposition time is 20 minutes, and the Bi2Se3 thin film precursor is deposited.

[0044] S5, post-tellurization treatment:

[0045] The Bi2Se3 film precursor obtained in S4 and 0.01g Te particles (99.999%) were placed in a quartz tube and vacuumed to 4×10 -3 Pa was vacuum sealed, and then placed in a box furnace and heated for 30 minutes at a temperature of 350 ° C. After cooling, it was taken out to obtain Bi2Se 3-x Te y Thermoelectric film, where x is 0.52 and y is 0.71.

[0046] Example 2

[0047] The difference from Example 1 is that S5, post-tellurization treatment:

[0048] The Bi2Se3 film precursor obtained in S7 and 0.01g Te particles (99.999%) were placed in a quartz tube and vacuumed to 4×10 -3 Pa was vacuum sealed, and then placed in a box furnace and heated for 60 minutes at a temperature of 350 ° C. After cooling, it was taken out to obtain Bi2Se 3-x Te y Thermoelectric film, where x is 1.26 and y is 1.51.

[0049] Example 3

[0050] The difference from Example 1 is that S5, post-tellurization treatment:

[0051] The Bi2Se3 film precursor obtained in S7 and 0.01g Te particles (99.999%) were placed in a quartz tube and vacuumed to 4×10 -3 Pa was vacuum sealed, and then placed in a box furnace and heated for 90 minutes at a temperature of 350 ° C. After cooling, it was taken out to obtain Bi2Se 3-x Te y Thermoelectric film, where x is 1.38 and y is 1.6.

[0052] Experimental testing

[0053] The Bi2Se3 thin film precursor prepared in Example 1 (heated for 0 min) and the Bi2Se3 thin film precursor prepared in Examples 1 to 3 after tellurization were compared. 3-x Te y The thermoelectric film (heated for 30min, 60min and 90min respectively) was subjected to X-ray diffraction (XRD) test. The test results are as follows: Figure 2 As shown. Figure 2 It can be seen that the diffraction peaks of the Bi2Se3 film precursor are well aligned with the Bi2Se3 standard card (PDF#33-0214) and show a high degree of c-axis orientation. 2.48 Te 0.71 、Bi2Se 1.74 Te 1.51 、Bi2Se 1.62 Te 1.6 Thermoelectric thin film samples.

[0054] The Bi2Se3 thin film precursor prepared in Example 1 (heated for 0 min) and the Bi2Se3 thin film precursor prepared in Examples 1 to 3 after tellurization were compared. 3-x Te y Thermoelectric film (heated for 30min, 60min and 90min respectively) was tested for element distribution. The test results are as follows Figure 3 and Figure 4 shown.

[0055] Depend on Figure 3 As can be seen from (e), (f) and (g) in the figure, the scanning electron microscope element energy spectrum shows that the Bi, Se and Te elements in the thermoelectric film are evenly distributed in the film, proving that the entire Bi2Se3 film precursor is uniformly tellurized.

[0056] Depend on Figure 4It can be seen that the Bi2Se3 thin film precursor is composed of two elements, Bi and Se, with an atomic ratio of 2:3.01. After tellurization, the atomic ratios are Bi:Se:Te=2:2.48:0.71, 2:1.74:1.51 and 2:1.62:1.6, which are higher than the traditional high-performance n-type Bi2Se 0.3 Te 2.7 The material's use of Te element is greatly reduced.

[0057] The Bi2Se3 thin film precursor prepared in Example 1 (heating for 0 min) and the Bi2Se3 thin film precursor prepared in Examples 1 to 3 after tellurization 3-x Te y Thermoelectric performance of the thermoelectric film was tested (heating for 30min, 60min and 90min respectively). Figure 5 、 Figure 6 and Figure 7 shown.

[0058] Among them, Bi2Se obtained after 60min of tellurization 1.74 Te 1.51 The power factor of the thin film sample at room temperature was increased to 20.74 μW·cm -1 K -1 , compared with Bi2Se3 thin film precursor (3.38μW·cm -1 K -1 ) increased by 513.6%, showing excellent thermoelectric performance.

[0059] Therefore, the present invention adopts the above-mentioned method for preparing Bi2Se3 thin films with high power factor based on post-tellurization treatment, which has a simple preparation process and good repeatability, and obtains a room temperature thermoelectric power factor of up to 20.74μW·cm -1 K -1 Bi2Se 3-x Te y Thermoelectric film, which has broad application prospects in areas such as self-powered wearable devices.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment, characterized in that: The following steps are involved: S1. Target preparation: Bi particles and Se particles are mixed uniformly according to a certain ratio, sealed in a tube, melted and sintered to obtain an ingot, which is crushed and pressed using a plasma discharge sintering technique to obtain a Bi2Se3 polycrystalline target; S2. Place the substrate and target: Place the Bi2Se3 polycrystalline target obtained in S1 on the sputtering target position of the PLD system chamber. At the same time, fix the ultrasonically cleaned substrate in the center of the sample tray and adjust the distance between the substrate and the Bi2Se3 polycrystalline target to 5-10 cm. S3. Adjust the vacuum degree: Pump the vacuum degree in the PLD system chamber to be equal to or less than 4×10 -4 After the pressure reaches 1500 Pa, high-purity argon gas is filled in, and the dynamic equilibrium pressure of the argon gas is kept stable by controlling the gas flow rate; S4. Thin film deposition: adjusting the deposition temperature, laser energy density, and laser frequency to pre-sputter the Bi2Se3 polycrystalline target to obtain a Bi2Se3 polycrystalline target with surface impurities removed, then opening the substrate baffle to deposit a Bi2Se3 thin film precursor; S5, post-tellurization treatment: according to the proportion, the Bi2Se3 film precursor obtained in S7 and Te particles are vacuum sealed, and then heated for 5-120min, and then taken out after cooling to obtain Bi2Se 3-x Te y Thermoelectric thin films.

2. The method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to claim 1, characterized in that: S1 includes the following steps: S11, mixing Bi particles and Se particles uniformly according to a certain proportion and placing them into a quartz tube for sealing; S12, placing the sealed quartz tube into a muffle furnace for melting and sintering at a temperature of 800-1000° C. for 5-24 hours to obtain an ingot; S13. The ingot is crushed and ground into powder, and then subjected to plasma discharge sintering at a sintering pressure of 10-50 MPa, a sintering temperature of 400-600° C., and a sintering time of 10-60 min, and pressed to obtain a Bi2Se3 polycrystalline target.

3. The method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to claim 1, characterized in that: In S2, the substrate is one of a single crystal Al2O3 substrate, an amorphous SiO2 substrate, a mica substrate, and a high temperature resistant polyimide substrate.

4. The method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to claim 1, characterized in that: In S3, the dynamic equilibrium pressure of the argon gas is 1-50 Pa.

5. The method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to claim 1, characterized in that: In S4, the deposition temperature is 200-450°C, and the laser energy density is 1.0-1.5 J / cm 2 , the laser frequency is 1-5Hz.

6. The method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to claim 1, characterized in that: In S5, the mass ratio of the Bi2Se3 thin film precursor to the Te particles is 1:50-500, and the purity of the Te particles is not less than 99.99%.

7. The method for preparing a high power factor Bi2Se3 thin film based on post-tellurization treatment according to claim 1, characterized in that: In S5, the vacuum sealing treatment uses a vacuum degree lower than 4×10 -3 The quartz tube of Pa is heated by a tube or box furnace at a temperature of 250-450°C.

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