YBa $_2$ Cu $_3$ O $_{7-\delta }$ -CeO $_2$ -YBa $_2$ Cu $_3$ O $_{7-\delta }$ 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 YBa 2 Cu 3 O 7-δ (YBCO), 75-nm CeO 2 , 150-nm YBCO, and 20-nm CeO 2 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 CeO 2 insulating layer exhibited hopping conduction that freezes out at low temperature, making these structures suitable for electrical circuits with isolated ground planes.