In this work, micro-structural and interfacial studies of the epi-Si/gamma-Al2O3 heterostructure were undertaken by spectroscopic ellipsometry, and compared with the results of atomic force microscopy and X-ray photoelectron spectroscopy. The experimental ellipsometric data were fitted with the theoretical calculations using effective medium approximation for each layer of the structure. It was observed that the epitaxial silicon layer consists of a fraction of amorphous Si and crystalline Si. The percentage of amorphous silicon increases with the decrease of deposition temperature and with the increase of the deposition rate. The gamma-Al2O3 layer produces a hydrostatic pressure on the Si substrate and the amount of hydrostatic pressure was measured to be 8 x 10(9) dyn/cm(2). (c) 2005 Elsevier B.V. All rights reserved.