Dependence of crystallinity on oxygen pressure and growth mode of La0.3Sr1.7AlTaO6 thin films on different substrates

The influence of oxygen pressure on epitaxial quality of La0.3Sr1.7AlTaO6 (LSAT) films deposited by laser ablation on SrTiO3(100), LaAlO3(100), and MgO(100) substrates has been investigated. X-ray diffraction shows only (00l) peaks in the oxygen pressure range from 10−3 to 500 mTorr. However, the crystallinity of LSAT films is found to be sensitive to oxygen pressure and dependent on substrates. LSAT films on SrTiO3 have the narrowest full width at half maximum (FWHM) of 0.05° at 300 mTorr. The films on LaAlO3 exhibit a FWHM of 0.3° at 50–100 mTorr. On MgO substrate, significant improvement of crystallinity is achieved at 200–300 mTorr, but rocking curves give an FWHM of 0.70°–1.00° due to the large lattice mismatch between LSAT and MgO. Atomic force microscopy analyses demonstrate smooth LSAT surfaces without identified grains. Reflection high-energy electron diffraction studies suggest a two-dimensional growth mode for LSAT films on SrTiO3 and LaAlO3 and a three-dimensional growth mode for LSAT films on...