The native oxide, thermally oxidized and hydrofluoric acid rinsed surfaces of Si(100) have been characterized by photon stimulated ion desorption (PSD), and both photoelectron and Auger electron spectroscopies. The only species detected by PSD were H+ions with different kinetic energies. Low kinetic energy H+ions were detected only from the HF rinsed surfaces presumably arising from scission of Si—H bonds while higher kinetic energy ions attributed to adsorbed hydrocarbon dissociation were observed for all of the surfaces.