Preparation method of high-power-factor Bi2Se3 film based on post-tellurization treatment

Abstract

The invention belongs to the technical field of thermoelectric thin film materials, and particularly discloses a preparation method of a high-power-factor Bi2Se3 thin film based on post-tellurization treatment, and the preparation method comprises the following steps: S1, preparing a target material; s2, placing a substrate and a target material; s3, adjusting the vacuum degree; s4, depositing a thin film to obtain a Bi2Se3 thin film precursor; and S5, carrying out post tellurization treatment to obtain the Bi2Se3-xTe y thermoelectric thin film. The preparation method of the high-power factor Bi2Se3 thin film based on post-tellurization treatment is simple in preparation process and good in repeatability, the room-temperature power factor of the obtained Bi2Se3-xTey thermoelectric thin film is as high as 20.74 mu W.cm <-1 > K <-1 >, and the thin film has wide application prospects in the fields of self-power supply of wearable equipment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric thin film materials, and in particular to a high power factor Bi based on post-tellurization treatment. 2 Se 3 Method for preparing thin films. 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 light, 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] In the prior art, bismuth telluride (Bi 2 Te 3 ) is the only high-performance near-room temperature thermoelectric material that has been commercialized, but tellurium (Te) is expensive and its reserves in the earth's crust are only 0.001ppm. 2 Se 3 ), among which selenium (Se) is abundant in the earth's crust and cheap, but its low electrical properties make it unable to meet the needs of self-powered massive low-power electronic components in the era of the Internet of Things. Therefore, there is an urgent need for a method to retain Bi to the greatest extent. 2 Te 3 Thermoelectric thin film materials with high performance and low Te content are 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 high power factor Bi based on post-tellurization treatment 2 Se 3 The preparation method of the film has simple preparation process and good repeatability. 2 Se 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 , the film has broad application prospects in areas such as self-powered wearable devices.

[0005] To achieve the above object, the present invention provides a high power factor Bi based on post-tellurization treatment 2 Se 3 The method for preparing the film comprises the following steps:

[0006] S1. Target material preparation: Bi particles and Se particles are mixed evenly according to the proportion, and then sealed. The ingots are melted and sintered to obtain ingots. The ingots are crushed and pressed by plasma discharge sintering technology to obtain Bi 2 Se 3 Polycrystalline targets;

[0007] S2. Place substrate and target: Place the Bi obtained in S1 2 Se 3 The polycrystalline target is placed in the sputtering target position of the PLD system chamber, and the ultrasonically cleaned substrate is fixed in the center of the sample tray. 2 Se 3 The distance between polycrystalline targets is 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 1000 Pa, high-purity argon gas is filled in, and the dynamic equilibrium pressure of argon gas is kept stable by controlling the gas flow rate;

[0009] S4, thin film deposition: adjust the deposition temperature, laser energy density and laser frequency, 2 Se 3 Polycrystalline target is pre-sputtered to remove surface impurities from Bi 2 Se 3 Polycrystalline target, then open the substrate baffle and deposit Bi 2 Se 3 Thin film precursors;

[0010] S5, post-tellurization treatment: according to the proportion, the Bi obtained in S7 2 Se 3 The film precursor and Te particles are vacuum sealed, then heated for 5-120 minutes, and taken out after cooling to obtain Bi 2 Se 3-x Te y Thermoelectric thin films.

[0011] Preferably, S1 comprises the following steps:

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

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

[0014] S13, crushing the ingot and grinding it into powder, and then performing plasma discharge sintering, the sintering pressure is 10-50MPa, the sintering temperature is 400-600℃, the sintering time is 10-60min, and pressing is performed to obtain Bi 2 Se 3 Polycrystalline target.

[0015] Preferably, in S2, the substrate is a single crystal Al 2 O 3 Substrate, amorphous SiO 2 One of substrates such as substrate, mica substrate, high temperature resistant polyimide substrate, etc.

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

[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, Bi 2 Se 3 The mass ratio of the 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 sealing treatment uses a vacuum degree lower than 4×10 -3 The heating adopts a tubular or box-type furnace, and the heating temperature is 250-450°C.

[0020] Therefore, the present invention adopts the above-mentioned high power factor Bi based on post-tellurization treatment 2 Se 3 The method for preparing the film has the following beneficial effects:

[0021] The preparation process of the present invention is simple and has good repeatability. 2 Se 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 , the film has broad application prospects in areas such as self-powered wearable devices.

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

[0023] Figure 1 is a flowchart of an embodiment of a preparation method of a high power factor Bi 2 Se 3 thin film based on post-tellurization treatment of the present invention;

[0024] Figure 2 is a flowchart of an embodiment of a preparation method of a high power factor Bi 2 Se 3 X-ray diffraction pattern of an embodiment of a preparation method of a thin film based on post-tellurization treatment of the present invention;

[0025] Figure 3 is a flowchart of an embodiment of a preparation method of a high power factor Bi 2 Se 3 Scanning electron microscope image of an embodiment of a preparation method of a thin film based on post-tellurization treatment of the present invention, where (a) is a Bi 2 Se x thermoelectric thin film prepared with a tellurization time of 0 min, (b) is a Bi 2 Se x Te y (0 < x < 3, 0 < y < 2) thermoelectric thin film prepared with a tellurization time of 30 min, (c) is a Bi 2 Se x Te y (0 < x < 3, 0 < y < 2) thermoelectric thin film prepared with a tellurization time of 60 min, (d) is a Bi 2 Se x Te y (0 < x < 3, 0 < y < 2) thermoelectric thin film prepared with a tellurization time of 90 min, (e) is a Bi element distribution diagram, (f) is a Se element distribution diagram, and (g) is a Te element distribution diagram;

[0026] Figure 4 is a flowchart of an embodiment of a preparation method of a high power factor Bi 2 Se 3 Schematic diagram of atomic ratio of an embodiment of a preparation method of a thin film based on post-tellurization treatment of the present invention;

[0027] Figure 5 is a flowchart of an embodiment of a preparation method of a high power factor Bi 2 Se 3 Graph of the relationship between the power factor and temperature of an embodiment of a preparation method of a thin film based on post-tellurization treatment of the present invention;

[0028] Figure 6 is a flowchart of an embodiment of a preparation method of a high power factor Bi 2 Se 3 Graph of the relationship between the Seebeck coefficient and temperature of an embodiment of a preparation method of a thin film based on post-tellurization treatment of the present invention;

[0029] Figure 7 This invention is a high power factor Bi based on post-tellurization treatment 2 Se 3 A graph showing the relationship between conductivity and temperature in an embodiment of a method for preparing a thin film. DETAILED DESCRIPTION

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

[0031] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0032] Embodiment 1

[0033] A high power factor Bi based on post-tellurization treatment 2 Se 3 Thin films, such as Figure 1 As shown, the 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, crushing and grinding the melted ingot into powder, and sintering and pressing using plasma discharge sintering technology, with a sintering temperature of 500°C, a sintering pressure of 10 MPa, and a sintering time of 30 min to obtain Bi 2 Se 3 Polycrystalline target.

[0038] S2. Place substrate and target:

[0039] The Bi obtained by S1 2 Se 3 The polycrystalline target is placed in the sputtering target position of the PLD system chamber, and the single crystal Al 2 O 3 The substrate is glued to the center of the sample tray with silver glue. 2 O 3 The substrate was ultrasonically cleaned in anhydrous ethanol and deionized water three times, each time for 10 min, to adjust the single crystal Al 2 O 3Substrate and Bi 2 Se 3 The distance between the polycrystalline targets was 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 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 2Hz, for Bi 2 Se 3 Pre-sputtering of polycrystalline target to remove Bi 2 Se 3 The surface impurities of the polycrystalline target were removed. After 5 minutes, the substrate baffle was opened and the deposition time was 20 minutes. Bi 2 Se 3 Thin film precursors.

[0044] S5, post-tellurization treatment:

[0045] The Bi obtained by S4 2 Se 3 The film precursor and 0.01 g 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 Bi 2 Se 3-x Te y Thermoelectric film, where x is 0.52 and y is 0.71.

[0046] Embodiment 2

[0047] The difference from the first embodiment is that S5, post-tellurization treatment:

[0048] The Bi obtained by S7 2 Se 3 The film precursor and 0.01 g 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 Bi 2 Se 3-x Te yThermoelectric film, where x is 1.26 and y is 1.51.

[0049] Embodiment 3

[0050] The difference from the first embodiment is that S5, post-tellurization treatment:

[0051] The Bi obtained by S7 2 Se 3 The film precursor and 0.01 g Te particles (99.999%) were placed in a quartz tube and vacuumed to 4 × 10 -3 Pa was sealed in a vacuum tube, 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 Bi 2 Se 3-x Te y Thermoelectric film, where x is 1.38 and y is 1.6.

[0052] Experimental Testing

[0053] The Bi prepared in Example 1 2 Se 3 The film precursor (heating 0min) and the Bi prepared by tellurization in Examples 1 to 3 2 Se 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 Bi 2 Se 3 The diffraction peaks of the thin film precursor and Bi 2 Se 3 The standard card (PDF#33-0214) is well aligned and shows a high degree of c-axis orientation. 2 Se 2.48 Te 0.71 、Bi 2 Se 1.74 Te 1.51 、Bi 2 Se 1.62 Te 1.6 Thermoelectric thin film samples.

[0054] The Bi prepared in Example 1 2 Se 3 The film precursor (heating 0min) and the Bi prepared by tellurization in Examples 1 to 3 2 Se 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 shown in (e), (f) and (g), the scanning electron microscope element spectrum shows that the Bi, Se and Te elements in the thermoelectric film are evenly distributed in the film, proving that the entire Bi 2 Se 3 The thin film precursor is uniformly tellurized.

[0056] Depend on Figure 4 It can be seen that Bi 2 Se 3 The 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 is higher than the traditional high-performance n-type Bi 2 Se 0.3 Te 2.7 The material's use of Te element is greatly reduced.

[0057] Example 1 Bi prepared 2 Se 3 The film precursor (heating 0min) and the Bi prepared by tellurization in Examples 1 to 3 2 Se 3-x Te y Thermoelectric performance of the thermoelectric film was tested (heating for 30min, 60min and 90min respectively). The test results are as follows Figure 5 , Figure 6 and Figure 7 shown.

[0058] Among them, Bi obtained after 60 minutes of tellurization 2 Se 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 to 2 Se 3 Thin film precursor (3.38μW·cm -1 K -1 ) was increased by 513.6%, showing excellent thermoelectric performance.

[0059] Therefore, the present invention adopts the above-mentioned high power factor Bi based on post-tellurization treatment 2 Se 3 The film preparation method has a simple preparation process and good repeatability, and the room temperature thermoelectric power factor is as high as 20.74μW·cm -1 K-1 Bi 2 Se 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 solution of the present invention rather than to limit it. 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 solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution 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. Prepare target material: Mix Bi particles and Se particles uniformly according to proportion, seal the tube, melt and sinter to obtain an ingot, crush the ingot and press it by plasma discharge sintering technology to obtain Bi2Se3 polycrystalline target material; S2. Place substrate and target: Place the Bi2Se3 polycrystalline target obtained in S1 on the sputtering target position of the PLD system chamber, fix the ultrasonically cleaned substrate at 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 1000 Pa, high-purity argon gas is filled in, and the dynamic equilibrium pressure of 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, pre-sputtering the Bi2Se3 polycrystalline target to obtain the Bi2Se3 polycrystalline target with surface impurities removed, and 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 evenly according to proportion and putting them into a quartz tube for sealing treatment; S12, placing the sealed quartz tube into a muffle furnace for melting and sintering, the sintering temperature is 800-1000° C., the sintering time is 5-24 hours, and an ingot is obtained; S13, crushing the ingot and grinding it into powder, and then performing plasma discharge sintering, the sintering pressure is 10-50MPa, the sintering temperature is 400-600°C, the sintering time is 10-60min, and the Bi2Se3 polycrystalline target is obtained by pressing.

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 1-50Pa.

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 Bi2Se3 thin film precursor to Te particles is 1:50-500, and the purity of 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 of less than 4×10 -3 The heating adopts a tubular or box-type furnace, and the heating temperature is 250-450°C.

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