Epitaxial growth of SrTiO3 (0 0 1) films on multilayer buffered GaN (0 0 0 2) by pulsed laser deposition

SrTiO3 films were grown on CeO2/YSZ/TiO2 multilayer buffered GaN/Al2O3 (0 0 0 1) substrates with and without the YBa2Cu3O7-x (YBCO) bridge layer by pulsed laser deposition (PLD). The deposition process of the buffer layers was in situ monitored by reflection high-energy electron diffraction. The crystallographical orientation of the heterostructure was studied by x-ray diffraction (XRD). With the introduction of the YBCO (0 0 1) layer, the STO (0 0 1) film was epitaxially grown on the GaN substrate. There were three sets of inplane domains separated from each other by 30 degrees in both STO and YBCO buffer layers. The epitaxial relationship was STO (0 0 2)[1 1 0]parallel to YBCO(0 0 1)[1 1 0]parallel to CeO2(0 0 2)[0 1 0]parallel to YSZ (0 0 2)[0 1 0]parallel to GaN(0 0 0 1)[1 1 -2 0] according to XRD results. By comparing the orientation of STO grown on GaN with and without the YBCO top buffer layer, the surface chemical bonding was found to be a very important factor in determining the orientation relationship of STO.