Measurement of ion energy distributions in the bias enhanced nucleation of chemical vapor deposited diamond

In situ, real-time, mass selective energy analysis of the incoming ions has been carried out during bias enhanced nucleation for diamond chemical vapor deposition. The dependence of ion energies and fluxes as a function of the bias voltage and CH4 concentration was measured. The main ionic species that strike the substrate surface during bias enhanced nucleation have energies between 50 and 80 eV and are characterized by a low H content. When the bias is lowered to the value at which nucleation enhancement becomes negligible (100 V in our system), ions have an energy of about 30-40 eV, which is the critical value for penetrating below the surface of a hydrogenated amorphous carbon layer. These findings strongly support the subplantation model of bias enhanced nucleation. (C) 1999 American Institute of Physics. [S0021-8979(99)00522-8].