ON NITROGEN INCORPORATION DURING PE-CVD OF DIAMOND FILMS

Nitrogen is one of the most widely studied impurities in diamond films . The reason is that nitrogen takes part in a number of defects and th erefore has a deep influence on the optical and electrical properties of diamond films. The mechanism of nitrogen incorporation in diamond i s still an open question. This is mainly due to the complexity of the N-incorporation processes, depending not only on experimental paramete rs (e.g. type and concentration of the N-containing gas, substrate tem perature etc.) but also on the surface termination and on the orientat ion of the chemical vapor deposition (CVD) diamond film. The aim of th is paper is to compare nitrogen incorporation in CVD diamond films by addition of small amounts (ppm range) of two different N-containing pr ecursors--nitrogen and vaporised nitromethane--to a conventional CH4/H -2 gas mixture during microwave PE-CVD. Optical emission spectroscopy (OES) was used to survey the plasma chemistry during deposition. The r elative intensities of the H-beta atomic hydrogen emission line and of the CN and C-2 emitting radicals were recorded as a function of the n itrogen fraction added to the plasma. The influence of nitrogen incorp oration on the diamond film properties was investigated by a number of complementary techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), photothermal deflection spectroscopy (PDS-opt ical absorption) and Raman spectroscopy. (C) 1998 Elsevier Science S.A .