Preparation of epitaxial YBa 2Cu 3O 7− x/PrGaO 3 layered structures by means of a molecular beam epitaxy technique

Abstract

Using a molecular beam epitaxy (MBE) technique, PrGaO 3 (PGO) epitaxial films and YBa 2Cu 3O 7− x (YBCO)/PGO layered structures were successfully grown on SrTiO 3 (STO) (100) substrates. The reflection high-energy electron diffraction (RHEED) pattern and results of both the X-ray φ-scan and the X-ray θ–2θ scan show that the epitaxial relation of the YBCO/PGO layered structure on the STO (100) substrate was YBCO [001]‖PGO[110]‖STO[100]. The atomic force microscopy (AFM) image showed that the surface roughness value of the PGO film was less than 1 nm, and was sufficiently smooth for use as the buffer layer for YBCO on STO substrate. The surface roughness value of the PGO/YBCO/PGO structure was about 2 nm, and we found that the PGO/YBCO/PGO structure, which was deposited by using an MBE technique, has a smooth surface which can be used in layered devices. However, the T c of the YBCO layers in PGO/YBCO/PGO structures was about 20 K lower than that in PrBa 2Cu 3O 7− x (PBCO)/YBCO/PBCO structures, which had the same 12 nm thick YBCO layers. Improvement of the process will be necessary in order to obtain YBCO/PGO layered structures with good superconducting properties in future studies.