X-ray characterization of MgO thin films grown by laser ablation on SrTiO 3 and LaAlO 3

Abstract

Epitaxial thin films of MgO have been grown on single-crystal substrates of (1 0 0) oriented SrTiO 3 and LaAlO 3 by ablation of a Mg target in a molecular oxygen atmosphere using 1064 nm radiation from a Nd : YAG laser. Optimum growth was obtained with a substrate temperature of 500°C and an ambient oxygen pressure of 5×10 −5 Torr during ablation. X-ray θ–2 θ plots show that MgO films grow (1 0 0) oriented on both substrates. Pole figures indicate that MgO grows cube-on-cube on the SrTiO 3 substrate [MgO〈1 0 0〉||SrTiO 3〈1 0 0〉]. On LaAlO 3, the MgO lattice is rotated by 45° in plane with respect to the substrate lattice, with MgO〈1 1 0〉||LaAlO 3〈1 0 0〉. Symmetric and asymmetric area scans show that the MgO lattice is completely relaxed on both the SrTiO 3 and LaAlO 3 lattices. By depositing the MgO film without Q-switching the laser for a short initial period, a mixed (1 1 0) and (1 0 0) oriented MgO film was grown on LaAlO 3. The (1 1 0) orientation is bicrystalline, with in-plane orientations of MgO[1 1 0]||LaAlO 3[1 0 0] and MgO[1 0 0]||LaAlO 3[1 0 0].