Epitaxial Si thin films have been deposited by remote plasma enhanced chemical-vapor deposition at temperatures below 450 degrees C and at pressures between 50 and 500 mTorr. Growth rate data reveal the presence of two pressure dependent regimes for deposition process activation. Sampling of the plasma afterglow by mass spectrometry indicates a correlation between enhanced rates for single crystal film formation and the onset of an ion-induced surface H abstraction processes below pressures of similar to 200 mTorr. The role of low energy ions in the abstraction of chemisorbed H and its effects on the growth kinetics are discussed.