Adsorption and reaction of SiH4 and oxygen on Pd(1 1 1)

Coadsorption of SiH4 and oxygen on Pd(1 1 1) has been studied via temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), and Auger electron spectroscopy (AES). These techniques indicate that surface Si and O react at <200 K to form a surface SiOX layer that is stable to at least 950 K. TPD studies show trends indicating that surface Si reacts rapidly with surface O on Pd(1 1 1), such that Si-O bond formation occurs preferentially over H2O formation from reaction of surface H and O. HREELS studies provide direct evidence of Si and O bonding on the surface through characteristic Si-O vibrations. Some of these vibrations observed after high-temperature annealing may indicate a network of bonded Si-O atoms on the surface rather than isolated molecular adsorbates. AES gives further details of Si-O bonding through fine structure in the Si LVV spectra. CO was used as a probe molecule in both TPD and HREELS studies to study the effect of the SiOX partial overlayer on a well-characterized adsorbate on the Pd(1 1 1) surface. The annealed SiOX layer was found to primarily function by decreasing the number of CO desorption sites, rather than altering the CO adsorption state.