Oxide epitaxial lift-off of superconducting thin film devices

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 techn ique employs a YBCO release layer to separate the films from the growth sub strate. The critical development was the use of a polymer support layer whi ch retains sufficient compliance after curing to permit stress relaxation o f 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 w as accomplished by alternately depositing layers of strontium titanate and YBCO. Layer thicknesses were optimized to compensate for the resulting thro ugh-thickness stress gradient which developed due to thermal expansion diff erences.