Preparation method of middle and far infrared transparent conductive film

Abstract

The invention discloses a preparation method of a Bi2Te3 film, which comprises the following steps of: performing plasma chemical vapor deposition on a high-purity bismuth source and a high-purity antimony source on a clean substrate in vacuum at high temperature under the condition of introducing hydrogen to obtain a Bi2Te3 film crude product; the preparation of the Bi2Te3 film adopts an experimental method of plasma-assisted chemical vapor deposition, so that the deposition process can be carried out at a lower temperature, and compared with a traditional method, the Te evaporation phenomenon caused by too high temperature can be effectively avoided, and the vacancy defect density of Te in the film is reduced, thereby improving the crystallization quality of the Bi2Te3 film. According to the method, the Bi2Te3 thin film crude product is subjected to annealing treatment to remove H impurities in the Bi2Te3 thin film crude product, and the internal stress of the thin film is reduced through the treatment of naturally cooling to the room temperature, so that the high-quality Bi2Te3 single crystal thin film can be obtained. In addition, Bi2Te3 films with different shapes, sizes and thicknesses can be grown through the preparation method of the Bi2Te3 film, and industrial production and application are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of transparent conductive film preparation, and in particular relates to a method for preparing a mid- and far-infrared transparent conductive film. Background Art

[0002] Infrared transparent conductive films are widely used in military and civilian infrared detectors due to their excellent infrared transmittance and strong electromagnetic shielding capabilities, such as anti-interference infrared missile warheads, high-sensitivity infrared gas / CO detectors, etc.

[0003] Bi2Te3 three-dimensional topological insulator material has a bulk state with an insulator band gap and a surface state without a band gap. Moreover, the surface state can exist stably because it is protected by time reversal symmetry. Therefore, it appears to be conductive on the surface and insulating on the inside. Due to its unique surface state and transport properties, it can be used in many fields such as spintronic devices, high-frequency devices and quantum computing. However, no one has yet studied its infrared transparent conductive properties.

[0004] Existing transparent conductive films all have an inherent contradiction between high transmittance and low conductivity. The basic feature of Bi2Te3 three-dimensional topological insulator is that there are four time-reversal symmetric points in the Brillouin zone of its surface state, at which Kramers degeneracy occurs, forming a Dirac Cone. The vertex of the Dirac cone is called a Dirac point, and the dispersion relationship between energy and momentum near the vertex is linear (not a quadratic function). Due to the spin-coupling effect, the spin direction of the surface state is always perpendicular to the direction of momentum, allowing electrons to propagate on the surface with low loss (or no loss) at a speed similar to that of photons (surface mobility μ s ≈6000cm 2 / V·s), while its interior is in an insulating state. Therefore, Bi2Te3 three-dimensional topological insulator meets the requirements of high mobility of mid- and far-infrared transparent conductive films.

[0005] Researchers have used a variety of methods to prepare Bi2Te3 thin films, such as pulsed laser deposition, magnetron sputtering and chemical vapor deposition, but the disadvantages are that the preparation temperature is high and the saturated vapor pressure of Te is very high, which leads to the easy loss of Te and the formation of Te vacancies. Bi2Te3 containing Te defects can show good N-type semiconductor properties. This non-insulating "topological insulator" will produce a strong bulk conductivity background during electrical transport measurements, thereby masking the surface state conductivity characteristics and strongly affecting the transparent conductive properties of the topological insulator. Therefore, it is necessary to provide a preparation method that can improve the crystallinity of Bi2Te3 thin films. Summary of the invention

[0006] The present invention aims to solve the technical problem that the transparent conductive performance of Bi2Te3 film is strongly affected by the high vacancy defect density of Te in the Bi2Te3 film prepared by the prior art, and aims to provide a method for preparing Bi2Te3 film which can reduce the vacancy defect density of Te in the film and improve the crystallization quality of the film.

[0007] The preparation method of the Bi2Te3 film of the present invention comprises: in vacuum, high temperature and hydrogen, plasma chemical vapor deposition of high-purity bismuth source and high-purity tellurium source is carried out on a clean substrate to obtain a crude Bi2Te3 film.

[0008] Preferably, the temperature of the plasma chemical vapor deposition is 250-300°C.

[0009] Preferably, the radio frequency power of the plasma chemical vapor deposition is 250-300 W, the pulse frequency is 15-25 KHz, the pressure is 50-70 Pa, and the deposition time is 30-40 min.

[0010] Preferably, the method further comprises: after the plasma chemical vapor deposition, annealing the Bi2Te3 film crude product under an inert gas, and then naturally cooling it to obtain the Bi2Te3 film.

[0011] Preferably, the substrate is sapphire (0001);

[0012] Before the plasma chemical vapor deposition, the substrate is placed in an acetone solution, an anhydrous ethanol solution, and deionized water for ultrasonic cleaning, and each cleaning time is 10 to 15 minutes.

[0013] Preferably, the high-purity bismuth source is 98% trimethyl bismuth, and the high-purity tellurium source is 98% diethyl tellurium.

[0014] Preferably, the hydrogen flow rate of the high-purity bismuth source is 35-50 sccm, and the partial pressure ratio of the hydrogen to the high-purity bismuth source is 85:1-98:1; the hydrogen flow rate of the high-purity tellurium source is 95-120 sccm, and the partial pressure ratio of the hydrogen to the high-purity tellurium source is 75:1-90:1; the partial pressure ratio of the high-purity bismuth source to the high-purity tellurium source is 1:3-1:5.

[0015] Preferably, the annealing treatment refers to placing the Bi2Te3 film crude product in a molybdenum boat and annealing it in an annealing furnace, the annealing temperature is 250-350°C, and the annealing time is 30-40 minutes.

[0016] Preferably, the plasma chemical vapor deposition chamber is first evacuated to 1×10 -4 ~4×10 - 4Pa, and then use a molecular pump to evacuate the plasma chemical vapor deposition chamber to 3×10 -6 ~6×10 -6 Pa.

[0017] The positive and progressive effects of the present invention are:

[0018] The preparation of the Bi2Te3 film of the present invention adopts a plasma-assisted chemical vapor deposition method. The plasma generated during the plasma chemical vapor deposition process can significantly promote the chemical reaction, so that the deposition process can be carried out at a lower temperature. Compared with the existing preparation method, it can effectively avoid the Te evaporation phenomenon caused by excessively high temperature, reduce the vacancy defect density of Te in the film, and thus improve the crystallization quality of the Bi2Te3 film.

[0019] The present invention performs annealing treatment on the crude Bi2Te3 film product to remove H impurities in the crude Bi2Te3 film product, and reduces the internal stress of the film by naturally cooling it to room temperature, thereby obtaining a high-quality Bi2Te3 single crystal film. In addition, the preparation method of the Bi2Te3 film of the present invention can grow Bi2Te3 films of different shapes, sizes and thicknesses, which is conducive to industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The X-ray diffraction pattern of the Bi2Te3 thin film obtained in the embodiment of the present invention;

[0021] Figure 2 The surface morphology of the Bi2Te3 film obtained in the embodiment of the present invention;

[0022] Figure 3 X-ray photoelectron spectrum of the Bi2Te3 thin film obtained in the embodiment of the present invention;

[0023] Figure 4 The carrier concentration, mobility, resistivity-temperature diagram of the Bi2Te3 thin film obtained in the embodiment of the present invention;

[0024] Figure 5 The ultraviolet-visible light absorption-transmission spectrum, bandgap width and infrared transmission spectrum of the Bi2Te3 thin film obtained in the embodiment of the present invention;

[0025] Figure 6 It is a schematic diagram of the PN junction and current-voltage characteristic curve prepared based on the Bi2Te3 thin film of the present invention. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] The present invention provides a method for preparing a mid-to-far infrared transparent conductive film, comprising: depositing a high-purity bismuth source and a high-purity tellurium source by plasma chemical vapor deposition on a clean substrate under vacuum, high temperature and hydrogen to obtain a crude Bi2Te3 film. The specific steps of the Bi2Te3 film preparation method of the present invention are as follows:

[0028] Example Preparation of Bi2Te3 Thin Film

[0029] Step S1: Place the substrate S 衬底 The samples were placed in acetone solution (90%), anhydrous ethanol solution and deionized water for ultrasonic cleaning. The cleaning time for each cleaning was t 清洗 min, and then use a nitrogen gun to clean the substrate S 衬底 Blow dry and place in the chamber of plasma chemical vapor deposition equipment, and heat to the preset deposition temperature T 沉积 ℃ and keep this temperature stably. Trimethyl bismuth (TMBi, 98%) and diethyl tellurium (C4H10Te, 98%) are placed in diffusers in the chamber of the plasma chemical vapor deposition equipment respectively.

[0030] Step S2: first use the mechanical pump of the plasma chemical vapor deposition equipment (plasma enhanced chemical vapor deposition system (Orion III) produced by Trion Corporation of the United States) to evacuate the plasma chemical vapor deposition chamber to P1 Pa, and then use the molecular pump on the plasma chemical vapor deposition equipment to evacuate the chamber of the plasma chemical vapor deposition equipment to P2 Pa. Turn on the power supply of the RF pulse generator on the plasma chemical vapor deposition equipment and adjust the RF power to P 射频 W, pulse frequency is f 脉冲 KHz, so that a stable plasma is generated in the plasma chemical vapor deposition chamber.

[0031] Step S3, open the high-purity hydrogen valve to introduce high-purity hydrogen (99.999%), adjust the hydrogen flow rate of trimethyl bismuth (TMBi, 98%) in the diffuser to V1sccm, adjust the hydrogen flow rate of diethyl tellurium (C4H 10 Te, 98%)) with a hydrogen flow rate of V2sccm, trimethylbismuth (TMBi, 98%) and diethyltellurium (C4H 10 Te, 98%) were respectively TMBisccm、V C4H10Te sccm flow enters the substrate S 衬底 In the chamber of the plasma chemical vapor deposition equipment, it should be noted that the partial pressure ratio of hydrogen to trimethyl bismuth (TMBi, 98%) is R1; the partial pressure ratio of hydrogen to diethyl tellurium (C4H10Te, 98%) is R2, and the partial pressure ratio of trimethyl bismuth (TMBi, 98%) to diethyl tellurium (C4H10Te, 98%) is R3.

[0032] Step S4: Adjust the pressure of the chamber of the plasma chemical vapor deposition equipment to P3 Pa and the deposition time to t 沉积 min to obtain a crude Bi2Te3 thin film of suitable thickness.

[0033] Step S5, placing the crude Bi2Te3 film obtained in step S4 in a molybdenum boat and placing it in an annealing furnace (Hefei Kejing tube furnace OTF-1200X), annealing in high-purity nitrogen (99.999%) to remove H impurities in the film, and setting the temperature of the annealing furnace at V 升温 The heating rate is increased to T 退火 ℃ and maintain this temperature t 退火 min, and after the annealing treatment, the film is allowed to cool naturally to room temperature in the annealing furnace to obtain a Bi2Te3 film. The above parameters are shown in Table 1.

[0034] Table 1 Experimental parameters for preparing Bi2Te3 thin films in Example

[0035]

[0036]

[0037] Performance Test Example

[0038] The performance of the Bi2Te3 film prepared in the embodiment was evaluated, and the evaluation results are shown in Table 2. It should be noted that the specific method for evaluating the performance of the Bi2Te3 film of the present invention is: the obtained Bi2Te3 film is placed in an X-ray diffractometer (Bruker D8 X-ray diffractometer, Germany) to test the crystal structure and crystal orientation of the film, an infrared Fourier spectrometer (Shimadzu Fourier transform infrared spectrometer IRTracer-100, Japan) to test the infrared transmittance of the film, and a Hall effect tester (NanometricsACCENT HL55OOPC) to test the surface resistivity of the film.

[0039] Table 2 Performance evaluation results of Bi2Te3 films obtained in Example

[0040]

[0041] Table 3 Performance evaluation results of other existing infrared transparent conductive films

[0042] Transmittance Minimum surface resistivity at room temperature Crystallinity <![CDATA[CuScO2 thin film]]> 3~5μm 85% 1.047Ω·cm 96％ <![CDATA[CuSc 0.94 Sn 0.06 O2 Film]]> 3~5μm 90% <![CDATA[5.6×10 -2 Ohm cm]]> 90％ <![CDATA[In2O3:HfO2 thin film]]> 3~5μm 68% <![CDATA[3.3×10 -2 Ohm cm]]> none <![CDATA[In2O3:W thin film]]> 0.78~2μm 75% <![CDATA[3.23×10 -4 Ohm cm]]> polycrystalline <![CDATA[Y2O3:Ru thin film]]> 3.5~12μm 65% <![CDATA[3.36×10 -3 Ohm cm]]> Amorphous

[0043] The performance test diagram of the embodiment is as follows Figures 1 to 6 As shown, Figure 1 The X-ray diffraction pattern of the Bi2Te3 thin film in the embodiment is as follows: Figure 2 The atomic force microscope image, high-resolution transmission electron microscope image and selected area electron diffraction image of Bi2Te3 thin film are shown in Figure 2. Figure 3 is the X-ray photoelectron spectrum of Bi2Te3 thin film. Figure 1 (X-ray diffraction spectrum) shows that the Bi2Te3 film obtained in the embodiment of the present invention is a single crystal film with a high degree of c-axis preferred orientation. Figure 4 (Resistivity-temperature diagram) It can be seen that the minimum surface resistivity of the Bi2Te3 film obtained in the embodiment of the present invention is 7.5×10 -4 Ω·cm, it can be seen that the Bi2Te3 film obtained in the embodiment of the present invention has good electrical conductivity at room temperature. Figure 5 (Infrared transmission spectrum) It can be seen that the Bi2Te3 film obtained in the embodiment of the present invention has high crystallinity and good mid- and far-infrared transmittance.

[0044] According to the test results of the Bi2Te3 film obtained in the above embodiment, Table 1 shows that the Bi2Te3 film obtained in the present invention is a single crystal film with a high c-axis preferred orientation growth. At the same time, the film has good transmittance in the mid- and far-infrared bands and also has good electrical conductivity at room temperature. In other words, the Bi2Te3 film in the present invention is used as a wide-band infrared transparent conductive film, taking into account both electrical conductivity and wide-band transparency, and successfully overcomes the inherent contradiction between high transmittance and low conductivity in existing wide-band transparent conductive films. Comparing the data in Table 2 and Table 3, it can be seen that the Bi2Se3 infrared transparent conductive film prepared by the present invention has higher crystallinity, higher infrared transmittance and wider infrared wave spectrum transmission range than the existing infrared transparent conductive film, and also has lower resistivity. This shows that the Bi2Te3 infrared transparent conductive film prepared by the present invention is a wide-band high transmittance infrared transparent conductive film with good electrical conductivity. Since the Bi2Te3 film of the present invention has excellent optical transmittance and strong electromagnetic shielding, the Bi2Te3 film prepared by the present invention is expected to be used in various civilian and military infrared detectors. In addition, the Bi2Te3 film prepared by the present invention can also be used in diode devices. The performance evaluation method is to put the N-Bi2Te3 / P-CuScO2 diode device into the SDHG-186A variable frequency transformer volt-ampere characteristic tester to test the diode's volt-ampere characteristic curve. The evaluation results are as follows: Figure 6 It should be noted that the detectors and diodes described in the above applications are manufactured according to conventional methods in the prior art, and will not be described in detail here.

[0045] The present invention is described in detail above in conjunction with the embodiments of the accompanying drawings. A person skilled in the art can make various variations of the present invention according to the above description. Therefore, some details in the embodiments should not be construed as limiting the present invention, and the present invention shall be protected by the scope defined by the attached claims.

Claims

1. A method for preparing a mid- and far-infrared transparent conductive film, characterized in that The method comprises: in vacuum, high temperature and hydrogen gas flow, plasma chemical vapor deposition of high-purity bismuth source and high-purity tellurium source is carried out on a clean substrate to obtain a crude Bi2Te3 thin film.

2. The method according to claim 1, characterized in that The temperature of the plasma chemical vapor deposition is 250-350°C.

3. The method according to claim 1 or 2, characterized in that The radio frequency power of the plasma chemical vapor deposition is 200-250W, the pulse frequency is 20-30KHz, the pressure is 50-70Pa, and the deposition time is 30-40min.

4. The method according to claim 1 or 2, characterized in that The method further comprises: after the plasma chemical vapor deposition, annealing the Bi2Te3 film crude product under an inert gas, and then naturally cooling it to obtain the Bi2Te3 film.

5. The method according to claim 1 or 2, characterized in that The substrate is sapphire (0001); Before the plasma chemical vapor deposition, the substrate is placed in an acetone solution, an anhydrous ethanol solution, and deionized water for ultrasonic cleaning, and each cleaning time is 10 to 15 minutes.

6. The method according to claim 1 or 2, characterized in that The high-purity bismuth source is 98% trimethyl bismuth, and the high-purity tellurium source is 98% diethyl tellurium.

7. The method according to claim 6, characterized in that The hydrogen flow rate of the high-purity bismuth source is 35-50 sccm, and the partial pressure ratio of the hydrogen to the high-purity bismuth source is 85:1-98:1; The hydrogen flow rate of the high-purity tellurium source is 95-120 sccm, and the partial pressure ratio of the hydrogen to the high-purity tellurium source is 75:1-90:1; The partial pressure ratio of the high-purity bismuth source to the high-purity tellurium source is 1:3 to 1:

5.

8. The method according to claim 4, characterized in that The annealing treatment refers to placing the Bi2Te3 film crude product in a molybdenum boat and placing it in an annealing furnace for annealing, the annealing temperature is 250-350°C, and the annealing time is 30-45 minutes.

9. The method according to claim 1 or 2, characterized in that: First, use a mechanical pump to evacuate the plasma chemical vapor deposition chamber to 1×10 -4 ~6×10 -4 Pa, and then use a molecular pump to evacuate the plasma chemical vapor deposition chamber to 2×10 -6 ~5×10 -6 Pa.

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