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

Density-functional calculations have been performed to investigate,the reaction 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 (dimer mechanism) and at the S-B step (trough mechanism) were investigated. The desorption of hydrogen from the step edge is easier than that from the terrace. 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 radical is preferentially adsorbed at the step edge. The H abstraction from the 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.