Study On High Power Factor Bismuth Telluride Magnetron Sputtering Thermoelectric Thin Films

With the development of the Internet,the integration of electronic equipment is getting higher and higher,and the requirements for temperature control and heat dissipation of electronic components are becoming more and more demanding.Thermoelectric thin film devices with high flexibility and expansibility can realize local cooling,heating and power generation,and show good application potential in many fields such as thermal management of electronic components and self-power supply of sensors in the Internet of Things.However,the poor performance of thermoelectric thin films above the micron level seriously hinders their wide application.In this paper,the optimization of multi-target magnetron sputtering process for n-type Bi₂Te₃ thin films was firstly carried out,and a new layered sputtering process was developed.Four groups of 3μm Bi₂Te₃ thin films were prepared by changing the ratio of common sputtering layer to single target sputtering layer.It was found that Te atom diffused and induced grain growth along the layer during annealing due to excessive Te content at the bottom of the film prepared by layered sputtering.The preparation method of the innovative improved（00l）orientation factor and optimize the carrier concentration,3μm Bi₂Te₃ thin film best power factor～27mW/cm-K²,continue to use the hierarchical sputtering process of the preparation of 4μm Bi₂Te₃ thin film has the same high（00l）orientation and power factor.A large number of pores in 3μm and 4μm Bi₂Te₃ films can enhance the phonon scattering and reduce the thermal conductivity of the lattice,and the final ZT reaches～0.91 and～1.01 at room temperature,respectively.The thermoelectric properties of（Sb,Bi）₂Te₃ films are determined by the Te content in the matrix,because the inversion defect dominates the carrier concentration.By controlling the power,annealing temperature and time of the cosputtered Te target,the in-plane orientation of the film is enhanced,and the carrier concentration is controlled effectively.Studied Te content on the thermal performance of the system of dependencies,by adjusting the content of Te,optimization of carrier concentration and orientation,the preparation of 1.5 mu m Sb₂Te3 film power factor for～32mW/cm-K²,Bi_0.5 Sb_1.5 Te₃ film power factor for～36mW/cm-K²,The final ZT values were～0.49 and～0.58,respectively.Using stratified sputtering process preparation of four microns Sb₂Te₃ and Bi_0.5 Sb_1.5 Te₃ film,film power factor respectively～23.1mW/cm-K² and～24.5mW/cm-K²,ZT values of～0.47 and～0.93 respectively.An in-plane flexible thermoelectric thin film device was constructed by using 4μm Bi₂Te₃ film as n-type thermoelectric arm and（Sb,Bi）₂Te₃ film as p-type thermoelectric arm.When used in power generation mode,the maximum output power of binary and terpolymer thermoelectric thin film devices is 1.02μW and 4.28μW,respectively,at30K temperature difference.High power densities of 10.17W/m² and 113.6W/m²,respectively,show great potential for continuous charging of low power electronic devices;In refrigeration mode,binary and ternary thermoelectric thin film devices under vacuum environment can produce a maximum temperature difference of～4.2K and～6.3K respectively.By heating the sample under laser irradiation,the peak temperature of the ternary thermoelectric thin film device is reduced to 5.7K,proving its potential application in embedded refrigeration.