Epitaxial growth, structure, and intermixing at theLaAlO3/SrTiO3interface as the film stoichiometry is varied

${\mathrm{LaAlO}}_3$ epitaxial films with La:Al cation ratios ranging from 0.9 to 1.2 were grown on ${\mathrm{TiO}}_2$-terminated ${\mathrm{SrTiO}}_3$ (001) substrates by off-axis pulsed laser deposition. Although all films are epitaxial, rocking curve measurements show that the crystallographic quality degrades with increasing La:Al ratio. Films with La:Al ratios of 0.9, 1.0, and 1.1 were coherently strained to the substrate. However, the out-of-plane lattice parameter increases over this range, revealing a decrease in film tetragonality. Although all film surfaces exhibit hydroxylation, the extent of hydroxylation is greater for the La-rich films. Rutherford backscattering spectrometry reveals that La from the film diffuses deeply into the ${\mathrm{SrTiO}}_3$ substrate and secondary-ion-mass spectroscopy shows unambiguous Sr outdiffusion into the films.