Influence of deposition pressure (O2) on the YBCO (Y123) thin films prepared by pulsed laser deposition

Abstract

In this paper, the influence of oxygen pressure on film quality and superconducting properties of YBa2Cu3O7−δ(YBCO-Y123) thin films prepared by Pulsed Laser Deposition (PLD) was investigated. For this purpose, YBCO thin films were deposited on polished LaAlO3 (l00) (LAO) substrates at three different oxygen pressures (150, 200, and 250 mTorr). X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques were used to make comparative studies of film microstructure. Except for oxygen pressures, all other variables such as number of pulses, repetition rate, deposition temperature, heating and cooling rate, target-substrate distance, laser excitation energy, annealing temperature, and annealing pressure were fixed. For this fixed set of parameters, SEM, XRD analysis, and AC susceptibility measurements of these films revealed that the crystal structure quality and superconducting properties of YBCO thin films are optimum at the oxygen deposition pressure of 150 mTorr. As the deposition pressure increased, Y2BaCuO5 (Y211) phase peaks were seen in XRD patterns. The reason for this was believed to be caused by decreased concentration of CuO and BaO as determined by Energy Dispersive X-Ray Spectroscopy (EDX) of thin films. © Springer Science+Business Media New York 2012.