Methanol adsorption on silicon (001)

Using a first-principles pseudopotential technique, we have investigated the adsorption of CH3OH on the Si(0 0 1) surface. We have found that, in agreement with the overall experimental picture, the most probable chernisorption path for methanol adsorption on silicon (0 0 1) is as follows: the gas phase CH3OH adsorbs molecularly to the electrophilic surface Si atom via the oxygen atom and then dissociates into Si-OCH3 and H, bonded to the electrophilic and nucleophilic surface silicon dimer atoms, respectively. Other possible adsorption models and dissociation paths are also discussed. Our calculations also suggest that the most probable methanol coverage is 0.5 ML, i.e., one molecule per Si-Si dimer, in agreement with experimental evidences. The surface atomic and electronic structures are discussed and compared to available theoretical and experimental data. In addition, we propose that a comparison of our theoretical STM images and calculated vibrational modes for the adsorbed systems with detailed experimental investigations could possibly confirm the presented adsorption picture. (C) 2004 Elsevier B.V. All rights reserved.