High superconducting transition temperatures in sputter-deposited YBaCuO thin films

Abstract

The recent discovery of a remarkable new family of high critical temperature superconducting oxides has excited extraordinary interest and research activity worldwide1–6. The prospect of superconducting devices and machines operating in liquid nitrogen and at higher temperatures is seen as an unprecedented technological development. There are potential applications in microelectronics and computers, energy storage and transmission, transport, high technology engineering, sensors and instrumentation. For many applications it is essential to prepare these materials in the form of thin films on suitable substrates. Currently, most of the research effort and all of the available published information relates to the fabrication of bulk samples from powders. At Cambridge our primary objective has been to achieve the deposition of high-quality thin films. We have taken this course because, (1) deposition from a multi-target sputter system gives great flexibility and enables us to cast a wide parameter net in composition and temperature to ensure early identification of key superconducting phases, (2) the deposition and processing of 0.5 µm films can be carried out very rapidly with one or possibly more system cycles per day and (3) measurements on thin films provide quantitative information on basic superconducting parameters and are likely to lead to the first practical applications of these remarkable materials. Here we report preliminary results on the deposition of relatively homogeneous films with transition temperature onsets up to 99 K. First results are reported on film deposition conditions, film composition and structure, and on the effect of post-deposition anneals on superconducting properties.