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.