This study investigates the tensile-strained growth of LaAlO3 on SrTiO3(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, LaAlO3 films grow pseudomorphically. Plastic relaxation starts for films thicker than this critical thickness of 3.8 run. 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. (c) 2007 Elsevier B.V. All rights reserved.