Relaxed Ge buffer layers were grown on Si substrates using a recently developed chemical vapor deposition (CVD) approach that combines digermylmethane and digermane precursors. Ultrathin Si films were deposited on these buffer layers at 420 degrees C by CVD using trisilane as a precursor. The Si films were studied with a variety of experimental techniques, with emphasis on Raman spectroscopy. The analysis of the Raman results shows that a thin (<1 nm), fully strained Si-Ge alloy layer is formed at the Si-Ge interface. Pure Si grows on this transitional alloy with a strain that approximately follows the predictions from a simple equilibrium strain theory. These results are significant for Ge-based Metal-Oxide-Semiconductor applications that require a thin Si-layer to isolate the Ge channel from the high permittivity oxide. (C) 2008 Elsevier B.V. All rights reserved.