High-resolution photoemission study of ethanol on Si(100)2×1

The adsorption of ethanol on Si(100)2×1 has been investigated at room temperature by high-resolution synchrotron radiation photoemission, and a consistent picture has been obtained in favour of dissociative adsorption, from a comparison of the valence band for pure and adsorbed ethanol, which shows the disappearance of σOH orbital after adsorption, and from the identification of a SiO-related component in the Si 2p core spectrum. A line-shape analysis of the Si 2p complex envelope corresponding to different ethanol exposures identifies a second component, which grows with the exposure at a different rate, and is assigned to SiH bond. The values for relative quantitative ratios among the various components suggest an exposure-dependent adsorption mechanism for ethanol, characterized by the formation of stable SiO bonds and a high hydrogen surface mobility. The analysis of the C 1s photoemission core-line suggests that no CO bond rupture occurs, at variance with our previous findings for ethanol adsorption on Si(111)7×7.