INFLUENCE OF DEPOSITION PARAMETERS ON PROPERTIES OF LASER ABLATED YBa2Cu3O7-delta FILMS

YBa2Cu3O7-delta films have been laser ablated under a variety of conditions, onto four different substrate materials. Using scanning tunneling microscopy it was observed that the films grow by an island nucleation and growth mechanism. The properties of the films were studied as functions of the deposition conditions. Films on LaAlO3 had the best and most reproducible properties. The superconducting transition temperatures of films deposited on LaAlO3 proved to be fairly insensitive to the substrate temperature during deposition; T-c > 90 K were obtained for films deposited over a temperature range from 760 degrees to 850 degrees C. The oxygen partial pressure during the deposition had a large effect on the transition temperature; the highest T(c)s were obtained for films deposited in 26.7 Pa (200 mTorr) oxygen. Measurements of transport critical current indicate that films deposited at lower temperatures are less sensitive to magnetic fields, suggesting that they may contain more defects which act as flux pinning sites.