Strain relaxation and critical thickness for epitaxial LaAlO3 thin films grown on SrTiO3(001) substrates by molecular beam epitaxy

Abstract This study investigates the tensile-strained growth of LaAlO 3 on SrTiO 3 (0 0 1) substrates by molecular beam epitaxy (MBE). Reflection high energy electron diffraction (RHEED) analysis shows that for thicknesses smaller than 3.8 nm, LaAlO 3 films grow pseudomorphically. Plastic relaxation starts for films thicker than this critical thickness of 3.8 nm. The in- and out-of-plane lattice parameters of the strain-relaxed layers have been measured by ex situ X-ray diffraction (XRD) at grazing angles. The relaxation mechanism is discussed on the basis of these experiments.