Density functional theory studies of submonolayer oxidized silicon structures on Pd(1 1 1) and Pt(1 1 1)

The stable structures formed by Si and O at submonolayer coverages on Pd(1 1 1) and Pt(1 1 1) were explored using density functional theory (DFT). Adsorbate structures with varying Si:O atom ratios and with total coverages between 2/9 ML and 1 ML were investigated. Although several oxidized silicon species are thermodynamically stable compared to atomic Si and O reactants, the most stable structure identified in this work is a continuous network of alternating Si-O bonds formed by an equal ratio of Si and O atoms. In this structure, Si atoms are bound to the metal surface with O atoms bridging between Si atoms. The geometries of the oxidized silicon structures are similar between the two surfaces, though many of the structures are stabilized on the Pt(1 1 1) surface versus the Pd(1 1 1) surface. Vibrational spectra calculated for various oxidized silicon adsorbates are compared to previous ultra high vacuum (UHV) studies on metal surfaces.