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◦ in both STO and YBCO buffer layers. The epitaxial relationship was STO (0 0 2)[1 1 0]_YBCO(0 0 1)[1 1 0]_CeO2(0 0 2)[0 1 0]_YSZ (0 0 2)[0 1 0]_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.