Epitaxial growth of Bi2Te3 topological insulator thin films by temperature-gradient induced physical vapor deposition (PVD)

Abstract

We report the growth of a high-quality Bi2Te3 thin film on an Al2O3 substrate using physical vapor deposition. Using a carefully selected temperature gradient between two separately controllable heaters inside a furnace, an unstrained Bi2Te3 thin film with c-axis orientation and domains bonded by van der Waals epitaxy is formed, as confirmed by X-ray diffraction. The stoichiometry of the film determined by X-ray photoelectron spectroscopy shows that the film has only slight surface oxidation and few contaminants, and the estimated ratio of the atomic densities of bismuth and tellurium is 1.49. A relatively low carrier concentration of 4.83 × 1018 cm−3 and electron mobility of 192.4 cm2/Vs at 3 K allow clear observation of the weak anti-localization effect. Using a traditional two-dimensional (2D) localization analysis with the original Hikami–Larkin–Nagaoka equation, we find clear evidence for the existence of topological surface states, and the temperature dependence of the phase coherence length exhibits 2D material behavior. Pronounced linear magnetoresistance at medium and high fields, which shows the interplay between three characteristic lengths, is also analyzed.