Improvement of energetic efficiency for homoepitaxial diamond growth in a H2/CH4 pulsed discharge

The use of pulsed discharges for diamond deposition has been demonstrated to ensure a better control of heat transfer from the plasma to the walls in microwave plasma reactors. It also favours the production of CH3 species while keeping constant or higher the H-atom density. Higher growth rates can then be obtained. In this paper is reported an increase of the growth rate by 25% while decreasing the input microwave mean power by 15%. These results are discussed in terms of atomic hydrogen and methyl radicals densities calculated with a unstationary 1-D axial plasma model. The results show in particular that the gas temperature, which directly controls atomic hydrogen production, needs a t(on) of around 8 ms to reach the steady state, and that 50% of atomic hydrogen is lost by recombination after a t(off), of 2 ms. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.