Bonding configurations of acetylene adsorbed on the Si(100)-2×1 surface predicted by density functional cluster model calculations

Abstract

We have used the hybrid density functional B3LYP method in combination with cluster surface models to study the adsorption of C₂H₂ on the Si(100)-2×1 surface. Four bonding configurations of C₂H₂ adsorption on a single Si dimer and on two neighboring dimers have been found. Two bonding configurations with C₂H₂ di-σ bonds result in high and comparable adsorption energies (>60 kcal mol⁻¹), whereas the two bonding configurations with C₂H₂ tetra-σ bonded over two neighboring Si dimers give lower, but substantial, adsorption energies centering around 44 kcal mol⁻¹. The calculated vibrational frequencies for the bonding configurations with C₂H₂ di-σ bonded structures are found to be in reasonable agreement with the experimental HREELS spectra reported in the literature (M. Nishijima, J. Yoshinobu, H. Tsuda and M. Onchi, Surf. Sci., 1987, 192, 383; C. Huang, W. Widdra, X. S. Wang and W. H. Weinberg, J. Vac. Sci. Technol. A, 1993, 11, 2250).