Ab initio calculations on etching of graphite and diamond surfaces by atomic hydrogen - art. no. 235311

Etching of graphite and hydrogenated diamond C(100) 2 x 1 surfaces by irrad iating atomic hydrogen, which is one of the key reactions to promote epitax ial diamond growth by chemical vapor deposition, has been investigated by a b initio pseudopotential calculations. We demonstrate the reaction pathways and determine the activation energies for breaking C-C bonds on the surfac es by irradiating hydrogen atoms. The activation energy for C-C bond breaki ng on graphite is found to be only one-half of that on the hydrogenated dia mond surface. This indicates that graphite, which is a typical nondiamond p hase unnecessarily generated on the diamond surface during epitaxial growth , can be selectively eliminated by atomic hydrogen, resulting in methane de sorption. Our result supports the growth rate enhancement in diamond epitax y observed in a recent experiment by gas-source molecular beam epitaxy unde r hydrogen beam irradiation.