Preparation of Y2Ba4Cu8O20−x thin films by thermal coevaporation

We report on the preparation of Y2Ba4Cu8O20−x (‘‘248’’) thin films by coevaporation using a combination of electron beam and Knudsen cell vapor sources. Our best film shows a superconducting onset at 80 K and zero resistance at 72 K. The x-ray diffraction patterns show nearly single phase ‘‘248’’ with a small YBa2Cu3O7−x (‘‘123’’) impurity. It has been our experience that films can be annealed at least twice without displaying any shift in diffraction peak position.