The aluminium induced layer exchange process is used for growing crystalline Si films on amorphous substrates like glass, which are further epitaxially thickened and can be used for photovoltaic applications. In this work we investigated Al2O3 membranes separating the Al and Si layer during the layer exchange by means of high-resolution transmission electron microscopy and studied the influence of the membranes' structure on crystallization of Si. We observed a phase transformation of the membrane from the amorphous state to gamma-Al2O3 at exchange temperatures at above 450 degrees C. At higher temperatures this transformations induces cracks into the thin membrane. We further discuss the influence of this phase transformation on the preferential orientation of the growing Si grains. (c) 2006 Elsevier B.V. All rights reserved.