To optimize Nb/Al-AlOx/Nb Josephson junctions, atomic force microscopy is used to study the morphology of dc magnetron-sputtered Nb and Al. When the intrinsic stress of Nb films is varied by adjusting Ar pressure, the roughness of Nb films is correlated with the intrinsic stress. Stress-free Nb films have a smooth surface, without depressions, and a roughness of 14.6 A. The roughness of Al deposited on the Nb films reflects the roughness of the underlying Nb, and an Al thickness of more than 40 A is needed to cover the Nb surface without interruption.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering