Micro-Raman studies of substrate temperature effects on pulsed laser deposition fabricated YBa2Cu3O7-x epitaxial thin films

Abstract

Micro-Raman spectroscopy has been used to analyse the substrate temperature effects on high temperature superconducting YBa2Cu3O7-x thin films grown by the in situ pulsed laser deposition method. In particular, the dependence of the epitaxy quality on substrate temperature Ts is studied. Our results reveal that films with the highest epitaxy degree are grown with substrate temperature Ts between 680 and 720°C, in good agreement with previous superconducting transition temperature measurements and x-ray diffraction analyses. In addition, the formation and distribution of impurities produced during growth are identified by Raman spectra and Raman imaging, and they are found to be more pronounced at higher substrate temperatures. Finally, localized Raman analysis has been performed to investigate the orientation of the single crystal grains in films grown at substrate temperature Ts > 760°C. It is confirmed that, within the experimental error of 3°, the crystal a/b-axes of these single crystal grains have a strong tendency to orient themselves along the crystal axis of the substrate, independent of their size, shape and orientation of the domain boundaries.