Effect of Vacuum Annealing on Orientation of Fluorite Films on Tilted-Axes Substrates

CeO₂ and Y:ZrO₂ (YSZ) fluorite films were deposited on NdGaO₃ (NGO) tilted-axes substrates by pulsed laser deposition technique after oxygen or vacuum annealing, the orientation features of the resulting films were studied. The fluorite films on oxygen-annealed substrates showed good agreement with the graphoepitaxial growth mechanism. An excessive tilt over the calculated values is observed for substrate tilt angles of 10°–15°, presumably as a result of generation of regular dislocations. On vacuum-annealed substrates the YSZ films showed no additional tilt, instead a re-orientation towards (012) and (013) crystallographic planes of the film is observed for tilt angles 13°–15° and 18°–20°, respectively. Similar effects are observed for CeO₂ films after relaxation at critical thickness. The CeO₂ films on vacuum annealed substrates are seeded with alignment of (111) plane with the (110) plane of the substrate instead of standard (001) CeO₂ plane. Some part of the CeO₂ grains is oriented with the (111) plane along the substrate surface. The angular vicinity of a small-index crystallographic plane to the graphoepitaxial tilt value may result in an “accidental” epitaxial alignment.