Chemisorption of Fluorine, Chlorine, HF, and HCl on the Diamond (100)2x1 Surface: An ab Initio Study

This work addresses mechanistic issues in halogen assisted diamond growth via ab initio molecular orbital calculations on halogenated and hydrohalogenated carbon clusters as models of dimer-reconstructed diamond (100)2x1 surfaces. The bond lengths and the C-X and XCC-H bond energies have been found along with the effects of lattice constraints. The present results indicate that adsorbed F and Cl should be rather strongly bound to diamond surfaces, at least in the low coverage limit. A comparison of the C-X bond energies with experimental measurements of the stability of adsorbed F and Cl leads to the conclusion that the surface C-X bond strength is greatly reduced at monolayer coverage, due to steric and/or electronic repulsion effects that cannot be adequately included in small cluster models. 60 refs., 3 figs., 8 tabs.