Micro-Raman spectroscopy on YBCO films during heat treatment

The oxygen content and the local oxygen arrangement of YBa2Cu3O7-x, (YBCO) thin films grown on NdGaO3 substrates have been monitored by micro-Raman spectroscopy. The analysis was performed during the heat treatment of the sample in air, with temperatures T, ranging between 20-300 degreesC. At T-a < 220 degreesC, the superconductivity of the samples was preserved, the critical temperature T, being in the range of 86-90.7 K. At higher heating temperatures, the zero voltage state was suppressed due to the loss of oxygen. Evidence of fully oxygenated phase domains was nevertheless observed, proving the existence of a multiphase structure. The dramatic changes in the electrical characteristics are thus attributed to grain boundary region de-oxygenation, revealing the important role of planar-type defects on the transport properties of the films.