The intensities of the optical spectral lines emitted from a Si(100) surface under Ar+ ion bombardment are studied as a function of the ion kinetic energy (1-5 keV) and the partial pressure of silane. In these experiments, the ion flux is held constant while either the bombardment energy or the partial pressure of silane is varied. The intensities of the spectral lines are normalized with respect to the intensity of the excited neutral silicon (Si I, 288 nm) optical line emitted from the clean Si surface. The intensities of excited neutral Si (Si I, 288 nm), molecular SiH (A(2)Delta-X(2)Pi, 414 nm), H Balmer beta (486 nm) and H Balmer gamma (434 nm) optical lines emitted from silane exposed Si surfaces follow a similar increasing trend with respect to increasing partial pressures of silane. During continuous silane exposures, the intensity of these four lines also increases with increasing ion kinetic energy. A qualitative explanation based on the adsorption and decomposition of silane on the Si surfaces can account for this behavior. In contrast to the monotonic increase of the above emission lines with greater incident kinetic energies and higher silane partial pressures, the normalized H Balmer alpha (656 nm) optical line exhibits unique behavior. The intensity of the Balmer alpha transition decreases with increasing incident ion kinetic energy at all measured partial pressures of silane. (C) 2004 American Vacuum Society.