Inelastic electron tunneling spectroscopy (IETS) is used to record the vibrational spectra of thin films of amorphous SiO, prepared by radio-frequency planar magnetron sputter deposition in argon. The SiO, films are incorporated as the insulating barriers in aluminium SiO,/lead tunnel junctions, with no prior or subsequent oxidation of the aluminium films. Peak assignments are presented by comparison with infrared, Raman, and neutron scattering data for bulk silica, and a plausible stoichiometry is proposed. The SiO, barriers can be considered as model glass substrates for further adsorption studies, and hence extend the analytical capabilities of IETS. 3703