Point Defect-Driven Switching of Conductivity Type in Bi2Te3 Films prepared by Atomic Layer Deposition

Abstract

Bismuth telluride (Bi2Te3) films have significant application prospects in future thin-film thermoelectric devices. Atomic layer deposition (ALD) offers significant advantages for the fabrication of high-performance nanoscale films due to its precise thickness control. However, due to the difficulty in synthesizing (Et3Si)2Te, there are relatively few reports on the preparation of Bi2Te3 based on ALD method. In this study, intrinsic Bi2Te3 films with thicknesses within 22 nm are successfully deposited on substrates with varying thicknesses of SiO2 by adjusting the number of ALD cycles (50-600). The results indicate that the thickness of amorphous SiO 2 can affect the crystallinity of films, thereby influencing the number of point defects in Bi 2 Te 3 , and causing the conversion between conductive types N-P to occur during heating and cooling. Based on the results of the thermoelectric performance tests, this study proposed the relevant transformation mechanism. The carrier concentration of the prepared Bi2Te3 films reach about 10 20 cm -3 at room temperature, and a maximum power factor of 24.727 μW•cm⁻ 1 •K⁻ 2 is achieved at 453 K. This study reveals the influence of nanoscale crystallinity differences on the thermoelectric properties of Bi2Te3 thin films.