Characterisation and lattice location of nitrogen and boron in homoepitaxial CVD diamond

Homoepitaxial diamond films were prepared by microwave plasma assisted chemical vapor deposition (CVD) on {100} and {111} substrates from gas mixtures of 0.5 and 1.5 vol.% CH4 diluted in H-2. One set of films was doped with boron by admiring trimethyleborate (TMB) with the reactant gas. The boron concentration ranged from 10 to 100 ppm in the gas phase. Another set of samples was doped with isotopic N-15 by admiring 50 ppm N-15(2) with the reactant gas. The films were characterised with respect to the incorporation and the lattice locations of the dopant atoms by nuclear reaction analysis (NRA) and ion channelling analysis. Both boron and N-15 were found to incorporate preferentially in the {111} growth sectors. The B/C ratios in the films were determined to be one order of magnitude less than the B/C ratios in the gas phase, and the N-15/C ratios in the films were about four orders of magnitude less than the N-15/C ratios in the reactant gas. Both dopants were found to occupy preferentially substitutional sites in the host lattice. A substitutional fraction of 0.9-1.0 was determined for the boron dopant, a fraction of about 0.8 was derived for the nitrogen dopant.