Study Of Preparation And Thermoelectric Performance Of Multicycle Bi₂Te₃/Sb₂Te₃ Heterogeneous Nanometer Thin Film

Thermoelectric refrigeration technology has a wide application prospect in the field of temperature control, electronic heat dissipation and chip cooling as a new type of green environmental protection technology. However, the low thermoelectric conversion efficiency restricts its development. And the refrigeration efficiency depends on the thermoelectric properties of thermoelectric materials. Therefore, improving the thermoelectric properties is an effective method to solve this issue. Bi2Te3 and Sb2Te3 have been concerned due to the best thermoelectric performance at room temperature. In addition, low dimension thermoelectric materials has been considered as one of the effective methods to improve the thermoelectric performance. Hence, the fabrication of nanoscale Bi2Te3 and Sb2Te3 film is very significant for the improvement of thermoelectric optimal value.In this paper, single Bi2Te3 thin films and Sb2Te3 film is fabricated by DC magnetron sputtering. And vacuum annealing furnace is used for annealing treatment. Hall measurement system is used to measure the conductivity of thin film at room temperature. Membrane structure is characterized using X-ray diffractometer(XRD). The surface morphology and composition are analyzed by scanning electron microscope(SEM) and EDS. The influences of the sputtering process parameters and the annealing parameters on the organization and thermoelectric performance of the film are studied.Results indicate that the film roughness and particle size increase with the increasement of annealing temperature for Bi2Te3 and Sb2Te3 film. Also, carrier concentration and mobility increase resulting in the conductivity increasing. Annealing treatment for two films is conducted at different temperature, it is found out that two film variations exhibit similarity. Grain size and roughness of thin film are increased after annealing treatment. When annealing temperature reaches to 400 ℃, the surface roughness of the film increases sharply. Annealing treatment leads to the decrease of film carrier concentration, while mobility changed irregular and the degree of change is less than the one of carrier concentration, so conductivity is on the decline. Te atoms evaporate in the process of heat treatment.Based on the single-layer film preparation technology, Bi2Te3/Sb2Te3 films are fabricated on the Si substrate using DC and RF magnetron sputtering in this study. Structure of the multilayer film is analyzed by TEM. And the thermoelectric performance is measured. Results show that the interface numbers of multilayer film lead to the increase of phonon scattering and decrease of thermal conductivity. Compared to thermoelectric performance of single Bi2Te3 thin film, the conductivities of single layer film and multilayer film decrease with the increase of annealing temperature. The increase of film crystallinity and decrease of defect lead to the rise of carrier concentration and mobility. Results show that the structure of the multilayer film improves the thermoelectric performance of the membrane.