SCREW DISLOCATIONS IN SUBSTRATES USED FOR HIGH-TEMPERATURE SUPERCONDUCTOR THIN-FILMS

Substrates for high temperature superconductor (HTSC) thin films were chemically etched in order to obtain pits and hillocks at the sites of the dislocations. The structures were imaged by both an atomic force microscope and an optical microscope. We found that the dislocation density in the bare substrate is comparable to the screw dislocation density in the HTSC films. Based on the shape and orientation of the pits we identify the defects in the substrate as screw dislocations.