Examination of MgO insulator thin films for high-Tc superconducting devices

Abstract We have examined feasibility of MgO thin films as an insulating layer in high- T c SFQ digital devices. When MgO thin films were prepared at 350 °C by RF magnetron sputtering on Y 0.9 La 0.2 Ba 1.9 Cu 3 O y (La–YBCO) thin films, they showed a rough surface and existence of (1 1 1) orientation. Employing a 10-nm-thick BaZrO 3 buffer layer on the La–YBCO films, we successfully fabricated MgO thin films with a flat surface. The prepared MgO thin film on the La–YBCO film had a dielectric constant of 11.5. La–YBCO thin films on the MgO thin films had (0 0  l ) orientation and in-plane alignment. It was also found that the MgO thin film had a lower etching rate than those for La–YBCO films and conventional insulating thin films such as SrSnO 3 and CeO 2 .