First-principle study on reactions of diamond (100) surfaces with hydrogenand methyl radicals

Density-functional calculations have been performed to investigate,the reac tion of diamond (100) surfaces with the hydrogen and methyl radical. In the present study, the plasma chemical-vapor deposition process using CH4/H-2, gas was considered. The reactions with vapor CH3 radicals on the terrace (d imer mechanism) and at the S-B step (trough mechanism) were investigated. T he desorption of hydrogen from the step edge is easier than that from the t errace. It is expected that the concentration of the surface dangling bond at the step edge is higher than that on the terrace; therefore, the CH3 rad ical is preferentially adsorbed at the step edge. The H abstraction from th e CH3 group at the step edge is easier than that on the terrace due to the steric repulsion with the adjacent K atom. The C2H5 group is formed on the surface as a by-product with the CH3 adsorption at the CH2 group.