We have previously reported on the low-temperature (T=300-475 degrees C) epitaxial growth of thin silicon films by hot-wire chemical vapor deposition on Si (100). We derived a phase diagram for Si epitaxy on Si (100). With dilute SiH4, epitaxial growth is seen until 50 nm thickness, while twinned epitaxial growth is seen even at 1 mu m thickness. Computer simulation of HWCVD growth suggests that oxygen incorporation is responsible for epitaxial breakdown. The model predicts that the silicon to oxygen ratio decreases with temperature and dilution ratio during the growth of the first monolayer of silicon. (c) 2005 Elsevier B.V. All rights reserved.