Buffer layers for high-T c thin films on sapphire

Abstract

Buffer layers of various oxides including CeO[sub 2] and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa[sub 2]Cu[sub 3]O[sub 7[minus][delta]] (YBCO) thin films. An ion beam channeling minimum yield of [approximately]3% was obtained in the CeO[sub 2] layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO[sub 2] was found to be the best one for YBCO thin films on R-plane sapphire. High T[sub c] and J[sub c] were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were approximately 4 m[Omega] at 77 K and 25 GHz. 19 refs., 10 figs.