Influence of subsurface oxidation on the structure, stability, and reactivity of grafted Si(111) surfaces

M. F. JUAREZ; F. A. SORIA; E. M. PATRITO; P. PAREDES-OLIVERA

AMER CHEMICAL SOC

Año: 2008 vol. 112 p. 14867 - 14867

We investigated the influence of intermolecular interactions and subsurface oxidation on the structure, surface bonding, and reactivity of compact monolayers of small organic and inorganic molecules bound to the Si(111) surface via Si-C, Si-N, and Si-O bonds. We considered the following modified surfaces: Si-CH3, Si-CCH, Si-CN, Si-CH2CH3, Si-OCH3, Si-OH, Si-NH2, Si-NHOH, and Si-ONH2. The highest hydrogen bond strength (7.5 kcal/mol) was observed for the (1×1) Si-NHOH monolayer. The (1×1) Si-CH2CH3 monolayer had the highest repulsion at the DFT level, 9.1 kcal/mol. However, inclusion of dispersion interactions yielded a repulsion of only 1.8 kcal/mol. Subsurface oxidation was investigated for -H, -CH3, and -CH2CH3 terminated surfaces with surface coverages of 100 and 50%. The oxidation of the third Si-Si backbond is considerably more exothermic than the oxidation of the first and second backbonds. For monolayers with a surface coverage of 50%, the oxidation of alkylated silicon atom