Oxygen at the interface of CVD diamond films on silicon

The oxygen incorporation at the interface between the silicon substrate and chemical vapour deposited (CVD) diamond films nucleated by the bias-enhanced nucleation (BEN) procedure has been studied by heavy-ion elastic recoil detection (ERD). Using standard process conditions for the realisation of heteroepitaxial films, oxygen with a concentration equivalent to about 1 nm SiO2 has been found, which was mainly incorporated during textured growth with a certain CO2 admixture to the process gas. By completely omitting CO2 during nucleation and growth, the oxygen at the interface can be reduced by nearly one order of magnitude to 6.3 x 10(15) at cm(-2), corresponding to 0.14 nm SiO2. Intentional addition of highly enriched (CO2)-O-18 to the gas phase shows that the oxygen incorporation is strongly enhanced during BEN with hydrocarbon in the gas phase. The results indicate that roughening of the surface, the deposition of SixOyCz phases and strong lateral inhomogeneities at the silicon interface may explain the coexistence of epitaxial crystallites and amorphous phases. It is suggested that a further reduction of the oxygen concentration at the interface may have consequences for an improved heteroepitaxy of diamond on silicon. (C) 1999 Elsevier Science S.A. All rights reserved.