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-Tc SFQ digital devices. When MgO thin films were prepared at 350°C by RF magnetron sputtering on Y0.9La0.2Ba1.9Cu3Oy (La–YBCO) thin films, they showed a rough surface and existence of (111) orientation. Employing a 10-nm-thick BaZrO3 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 (00l) 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 SrSnO3 and CeO2.