Electrical characteristics of rf-sputtered single-crystal niobium films

It is shown from measurements of the resistivity ratio (RR ≡ resistivity at room temperature divided by resistivity at 10°K), superconducting transition temperature, and transition-temperature width that high-quality single-crystal niobium films can be fabricated by rf sputtering. The observed dependence of RR on sample thickness indicates that the intrinsic electron mean free path increases with thickness. Superconducting characteristics are essentially thickness independent for films thicker than approximately 1000 Å.