THE PHYSICAL AND CHEMICAL-PROPERTIES OF ULTRATHIN OXIDE-FILMS

Thin oxide films (from one to tens of monolayers) of SiO2, MgO, NiO, A l2O3, FexOy, and TiO2 supported on refractory metal substrates have be en prepared by depositing the oxide metal precursor in a background of oxygen (ca 1 x 10(-5) Torr). The thinness of these oxide samples faci litates investigation by an array of surface techniques, many of which are precluded when applied to the corresponding bulk oxide. Layered a nd mixed binary oxides have been prepared by sequential synthesis of d issimilar oxide layers or co-deposition of two different oxides. Recen t work has shown that the underlying oxide substrate can markedly infl uence the electronic and chemical properties of the overlayer oxide. T he structural, electronic, and chemical properties of these ultrathin oxide films have been probed using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electron energy loss spectrosc opy (ELS), ion-scattering spectroscopy (ISS), high-resolution electron energy loss spectroscopy (HREELS), infrared reflectance absorption sp ectroscopy (IRAS), temperature-programmed desorption (TPD), scanning t unneling microscopy (STM), and scanning tunneling spectroscopy (STS).