Electronic and vibrational properties of ultrathin SiO2 films grown on Mo(112)

Ultrathin SiO2 films on Mo 112 were synthesized using different preparation procedures and characterized with ultraviolet photoelectron spectroscopy UPS , metastable impact electron spectroscopy MIES , and polarization modulation infrared reflection absorption spectroscopy PM-IRAS . By correlating the vibrational and electronic data, an assignment of the prominent spectral features are made. The physical properties of SiO2 films near one monolayer are influenced by the Mo substrate due to the Si-O-Mo linkages, whereas films greater than two monolayers show properties comparable to bulklike silica samples. The electronic and vibrational properties of the SiO2 thin films are strongly coverage dependent. The data show that highly ordered SiO2 films can be grown up to one monolayer, whereas films with a thickness of greater than one monolayer are amorphous.