Study On The Thermoelectric And Infrared Performances Of Bi₂Te₃-Based Thin Films

Bi2Te3 as semiconductor material with the best thermoelectric properties at room temperature have been widely studied and many researchers utilized these properties to realize intelligent control by integrating Bi2Te3 film structures in functional devices. For example, Bi2Te3 is used to reduce radiation on the surface of the target by thermoelectric conversion. In this dissertation, we studied both the thermoelectric properties and the infrared absorbing properties of the Bi2Te3-based films by means of preparation process optimization, subsequent heat treatment process and doping modification:1. The best optimum fabrication parameters of RF magnetron sputtering technology is studied for Bi2Te3 thin film. It is found that the films deposition time affects the temperature of the substrate so as to the film crystallization, and the sheet resistance is nonlinear related to the deposition time. The sputtering power can affect the sputtering particles energy and results in control of the films crystallization and sheet resistance. The sputtering pressure exists an optimal value of 0.6 Pa. When the argon gas flow is under 17 sccm, the crystallization and the sheet resistance of the films are low.2. The influence of Bi2Te3 film heat treatment on the thermoelectric properties and the infrared absorption performance is studied. For thermoelectric properties under different annealing time, the study found that the influence of annealing temperature is different, and the power factor of 16.48 μW/K2 cm for long annealing time(60 min) is greater than the power factor of 11.43 μW/K2 cm for short annealing time. In addition,with the increase of annealing temperature, the infrared absorption peak show a red-shift under a short period of annealing time, and shows a first red-shift then blue-shift under the long annealing time.3. The influence of the composition on thermoelectric properties and infrared absorption performance is also studied. Auto-dope model as well as Sn doping model is built and calculated by means of first-principles calculation. It is found that the maximum power factor of 6.41 μW/K2 cm is obtained at stoichiometric ratio 2.2:2.8, but the power factor can increase to 7.97 μW/K2 cm after Sn atoms doped. From the infrared spectrum we can also find that the auto-dope and Sn elements doping have a great effect on the intensity of infrared absorption, and the Sn elements doping can make theabsorption frequency significantly shift, which is more advantageous control than the auto-dope absorption frequency.In the view of the good thermoelectric performance and infrared absorption frequency control of Bi2Te3 film, its application in intelligent devices and power devices is expected.