High critical current density Y Ba2Cu3O7−δ thin films fabricated by ex situ processing at low pressures

Abstract

There is interest in probing the feasibility and possible advantages of making uniform andcost-effective long-length coated conductors through a low-pressure processing approach.The low-pressure approach, eliminating the boundary layer and gas flow considerations,consumes much less of the processing gases and offers the possibility of improveduniformity and faster growth rate of superconducting films. Here, we have fabricatedY Ba2Cu3O7−δ (YBCO) epitaxialfilms of thickness 0.1–1.0 µm on SrTiO3 single crystal substrates using ex situ post-deposition processing of co-evaporated Y,BaF2 and Cuprecursors in a controlled low-pressure gas mixture of oxygen and water vapour. Partial pressures of oxygen(PO2) and watervapour (PH2O) as low as 10 and 0.1 mTorr, respectively, were used. X-ray diffraction and scanning electron microscopyinspection were conducted for structure characterization of the films. High critical current densities(Jc) of at 77 K in self-field were obtained, yielding properties comparable to those ofin situ films and ex situ films processed under atmospheric pressure condition.