Preparation of LSAT and BZO insulating layer on superconducting ground plane for high- Tc device

Abstract

As an insulating layer between a superconducting ground plane and a base electrode of Josephson junctions for high- T c devices, (LaAlO 3) 0.3–(SrAl 0.5Ta 0.5O 3) 0.7 (LSAT) thin films and BaZrO 3 (BZO) thin films were studied. LSAT films deposited on LPE–YBCO and La–YBCO films exhibited columnar grain growth. Insertion of thin SrTiO 3 (STO) buffer layer between LSAT and YBCO was found effective to suppress this columnar grain growth. Although BZO films on LSAT and STO substrates had smooth surfaces with the average roughness R a∼0.2 nm, the film deposited on La–YBCO showed a rough surface and poor adhesion. By employing a thin STO or LSAT buffer layer between BZO and La–YBCO, the film adhesion and surface quality were much improved. The relative permittivity values of STO/LSAT/STO and STO/BZO/STO were 30 and 20, respectively, indicating a high potential of STO-buffered BZO for use as insulating layers in high- T c devices.