Oxide epitaxial lift-off of superconducting thin film devices

Abstract

Oxide epitaxial lift-off (OELO) has been successfully accomplished for thin single layer films of strontium titanate and multilayer films of strontium titanate and superconducting yttrium barium copper oxide (YBCO). The technique employs a YBCO release layer to separate the films from the growth substrate. The critical development was the use of a polymer support layer which retains sufficient compliance after curing to permit stress relaxation of the oxide film in such a way as to prevent cracking. Multilayer lift-off had the additional necessity of encapsulating the YBCO device layer. This was accomplished by alternately depositing layers of strontium titanate and YBCO. Layer thicknesses were optimized to compensate for the resulting through-thickness stress gradient which developed due to thermal expansion differences.