YBa2Cu3O7-δ-CeO2-YBa2Cu3O7-δ Multilayers Grown by Reactive Co-Evaporation on Sapphire Wafers

High-T-C superconductor thin film heterostructures were deposited using reactive co-evaporation for dual layer electronic applications. The epitaxial structure consisted of 35-nm YBa2Cu3O7-delta(YBCO), 75-nm CeO2, 150-nm YBCO, and 20-nm CeO2 on r-plane sapphire wafers. The critical temperature was measured to be 83.6 K and 84.8 K for the bottom and top YBCO layers, respectively. Atomic force microscopy reveals smooth surfaces with RMS roughness of the top YBCO layer to be 4.7 nm. The CeO2 insulating layer exhibited hopping conduction that freezes out at low temperature, making these structures suitable for electrical circuits with isolated ground planes.