Title :
Relationship of Nb surface morphology and Al coverage to the intrinsic stress of magnetron-sputtered Nb films
Author :
Tsukada, K. ; Kawai, J. ; Uehara, G. ; Kado, H.
Author_Institution :
Superconducting Sensor Lab., Chiba, Japan
fDate :
3/1/1993 12:00:00 AM
Abstract :
To optimize Nb/Al-AlO/sub x//Nb Josephson junctions, atomic force microscopy is used to study the morphology of DC magnetron-sputtered Nb and Al. The Nb film stress was sensitive to Ar pressure, and changed from compressive to tensile as the Ar pressure increased. The roughness of DC magnetron-sputtered Nb films was related to their internal stress. Stress-free Nb films have a smooth surface, without depressions, and a roughness of 14.6 AA. The roughness of the Al surface on Nb film was shown to reflect the roughness of the underlying Nb film, and was least for the stress-free Nb film. Coverage of Al was continuous for Al thicker than 40 AA. To make a fine Nb/Al-AlO/sub x//Nb Josephson junction, one should use a stress-free Nb film and deposit an Al layer at least 40 AA thick on the Nb films.<>
Keywords :
Josephson effect; atomic force microscopy; internal stresses; niobium; sputtered coatings; superconducting junction devices; superconducting thin films; surface topography; type II superconductors; Al film; DC magnetron-sputtered; Josephson junctions; Nb film; Nb-Al-AlO/sub x/-Nb junctions; atomic force microscopy; compressive stress; film stress; internal stress; intrinsic stress; stress-free film; superconducting thin films; surface morphology; tensile stress; Argon; Atomic force microscopy; Josephson junctions; Magnetic force microscopy; Niobium; Optical films; Rough surfaces; Surface morphology; Surface roughness; Tensile stress;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
