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

Micro-Raman spectroscopy has been used to analyse the substrate temperature effects on high temperature superconducting YBa2Cu3O7-x thin films grown b y the in situ pulsed laser deposition method. In particular, the dependence of the epitaxy quality on substrate temperature T-s is studied. Our result s reveal that films with the highest epitaxy degree are grown with substrat e temperature T-s between 680 and 720 degrees C, in good agreement with pre vious superconducting transition temperature measurements and x-ray diffrac tion analyses. In addition, the formation and distribution of impurities pr oduced during growth are identified by Raman spectra and Raman imaging, and they are found to be more pronounced at higher substrate temperatures. Fin ally, localized Raman analysis has been performed to investigate the orient ation of the single crystal grains in films grown at substrate temperature T-s > 760 degrees C. It is confirmed that, within the experimental error of 3 degrees, the crystal a/b-axes of these single crystal grains have a stro ng tendency to orient themselves along the crystal axis of the substrate, i ndependent of their size, shape and orientation oh the domain boundaries.