YBa2Cu3O7−x-Y2O3 system and in situ deposition of trilayer heterostructures by coevaporation

Abstract
We have deposited YBa2Cu3O7−x ‐Y2O3‐YBa2Cu3O7−x heterostuctures by an in situ electron‐beam coevaporation technique. Physical and chemical properties of Y2O3 were studied. The deposition conditions for Y2O3 and YBa2Cu3O7−x are completely compatible. The crystal structure of Y2O3 provides a close lattice match with YBa2Cu3O7−x and allows oxygen diffusion through Y2O3, so that heteroepitaxy and the tetragonal‐orthorhombic structural transformations of YBa2Cu3O7−x can be achieved. The heterostructures are therefore of high quality. Both the top and the bottom YBa2Cu3O7−x layers are superconducting above 85 K. Tunneling phenomena on junctions fabricated from these trilayers were observed.