Controllable preparation and superconducting properties of tantalum films with different orientations.

Transmon qubits based on α -Ta films have been demonstrated to possess long lifetimes, sparking significant interests among researchers in this material. In this study, we systematically investigated the growth conditions of α -Ta films on sapphire substrates. By controlling the growth temperature and power, we successfully prepared films with two distinct crystal orientations: α -Ta [110] and α -Ta [111]. We found that the growth conditions with low power and low temperature, as well as that with high power and high temperature, are conducive to the growth of α -Ta [110], while the low power combined with high temperature favors the growth of α -Ta [111]. The critical transition temperature T c of the [111]-oriented film increases more gently with the increase of residual resistance ratio (RRR) compared to the [110]-oriented film. Additionally, our result indicates that as the thickness of the α -Ta [111] film increases, the values of both T c and RRR rise, with the highest RRR value of 24.6. Our results provide important references for the preparation of high-quality α -Ta thin films. • High-quality Ta films with two orientations are grown controllably. • T c of [110] and [111] Ta films exhibits different evolutionary trends with RRR. • RRR increases with film thickness, showing a maximum value of 24.6. [ABSTRACT FROM AUTHOR]