Properties of High T sub c YbBa sub 2 Cu sub 3 O sub x Thin Films Prepared by Co-Evaporation

We have prepared superconducting thin film of high T sub c YbBa sub 2 Cu sub 3 O sub x by MBE techniques using evaporation of Cu, Yb and BaF sub 2 or Ba. The vacuum system used was designed for in situ oxidation and substrate heating with a simple two chamber configuration. We were able to maintain stable evaporation rates using all Knudsen cell sources: no real-time feedback shutter control was needed.