THICKNESS DEPENDENCE OF MICROWAVE SURFACE-RESISTANCE AND CRITICAL-CURRENT DENSITY IN AG-YBA2CU3O7-X THIN-FILMS

Microwave surface resistance and critical current density are measured in Ag-doped YBa2YBa2Cu3O7-x thin films as a function of thickness of the film. The microwave surface resistance decreases monotonically as the thickness of the film is increased to an optimum thickness of 3000 Angstrom. Beyond this optimum thickness the microstructure of the fil m deteriorates and the surface resistance increases as the thickness i s further increased. Critical current density also increases as the th ickness of the film is increased to the optimum thickness. The decreas e in the value of surface resistance and an enhancement of J(c) up to optimum thickness has been explained in terms of defects formed in the films during growth. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.