Temperature dependence of growth orientation of YBa2Cu3O6+δ film on NdGaO3 using liquid-phase epitaxy

Using a liquid-phase epitaxy method, YBa2Cu3O6+δ (YBCO) films were grown on NdGaO3 (NGO) substrates. Their growth orientation was investigated as a function of growth temperature. At growth temperatures higher than 980 °C, c-axis (YBCO〈0 0 1〉)-oriented films that were perpendicular to the substrate surface were obtained on both NGO(1 1 0) and NGO(0 0 1) substrates. At growth temperatures lower than 970 °C, YBCO films tended to grow with an a-axis orientation on NGO(1 1 0) substrates and a-/c-axis mixture film on NGO(0 0 1) substrates. It is difficult to explain these growth behaviors merely by the thermal expansion difference between the substrate and the film, supersaturation effect reported or strain energy caused by the misfit. Therefore, another factor affecting YBCO orientation with growth temperature and substrate orientation should be superimposed on these apparent factors.