Effects of post-annealing on crystalline and transport properties of Bi_2Te_3 thin films

A well-established method is highly desirable for growing topological insulator thin films with low carrier density on a wafer-level scale. Here, we present a simple, scalable method based on magnetron sputtering to obtain high-quality Bi₂Te₃ films with the carrier density down to 4.0×10¹³ cm^-2. In contrast to the most-used method of high substrate temperature growth, we firstly sputtered Bi₂Te₃ thin films at room temperature and then applied post-annealing. It enables the growth of highly-oriented Bi₂Te₃ thin films with larger grain size and smoother interface. The results of electrical transport show that it has a lower carrier density as well as a larger coherent length (~228 nm, 2 K). Our studies pave the way toward large-scale, cost-effective production of Bi₂Te₃ thin films to be integrated with other materials in wafer-level scale for electronic and spintronic applications.