Geometric and Electronic Structure of Epitaxial Iron Silicides

An internal reflection infrared cell has been employed to study aqueous hydrofluoric acid (HF) and ultraviolet (UV)/ozone processing of Si(100) surfaces in situ. The useful range of the infrared experiment was extended below 1500 cm^-1 to examine the Si—O--Si asymmetric stretching region by using a thin (75 /im) silicon single crystal in optical contact with a germanium internal reflection element. UV/ozone cleaning produces hydrophilic surfaces by oxidative removal of adventitious hydrocarbon on SiO₂ or by oxidation of hydrogen terminated silicon to SiO₂. Hydrophobic Si—H terminated surfaces are produced using dilute aqueous HF and are characterized by an increase in the intensity of the Si—H stretching mode and a concomitant decrease in the intensity of the Si---O—Si mode. UV/ozone oxidation of the HF treated surface produces oxidized silicon hydrides while removing Si—H and growing SiO₂. Where appropriate, comparisons will be made between the corresponding XPS and infrared spectra to demonstrate the complementary information provided by these spectroscopies.