High-quality superconducting α-Ta film sputtered on heated silicon substrate

Abstract: Intrigued by the discovery of the long lifetime in the {\alpha}-Ta/Al2O3-based Transmon qubit, researchers recently found {\alpha}-Ta film is a promising platform for fabricating multi-qubits with long coherence time. To meet the requirements for integrating superconducting quantum circuits, the ideal method is to grow {\alpha}-Ta film on a silicon substrate compatible with industrial manufacturing. Here we report the {\alpha}-Ta film sputter-grown on Si (100) with a low-loss superconducting TiNx buffer layer. The {\alpha}-Ta film with a large growth temperature window has a good crystalline character. The superconducting critical transition temperature (Tc) and residual resistivity ratio (RRR) in the {\alpha}-Ta film grown at 500 {\deg}C are higher than that in the {\alpha}-Ta film grown at room temperature (RT). These results provide crucial experimental clues toward understanding the connection between the superconductivity and the materials' properties in the {\alpha}-Ta film and open a new route for producing a high-quality {\alpha}-Ta film on silicon substrate for future industrial superconducting quantum computers.