A. Afzal et al., HFCVD DIAMOND GROWN WITH ADDED NITROGEN - FILM CHARACTERIZATION AND GAS-PHASE COMPOSITION STUDIES, DIAMOND AND RELATED MATERIALS, 7(7), 1998, pp. 1033-1038
Recently there has been considerable interest in the addition of nitro
gen to precursor gas mixtures and its influence on the properties of t
he resulting diamond films. Careful control of the nitrogen concentrat
ion in the CVD process results in changes to both the film growth rate
and morphology. In addition to the well-defined and precisely control
led deposition conditions, thorough characterization of the vapour-gro
wn material is indispensable in order to tailor diamond film propertie
s according to specific applications. High quality diamond films have
been produced via hot filament CVD (HFCVD) using a precursor gas mixtu
re of 1% methane in hydrogen with N-2 additions varying from 50 to 500
0 ppm (N/C 0.01-1.0). We report the results from both the structural a
nd compositional characterization of the as-deposited HFCVD diamond fi
lms by scanning electron microscopy, Raman spectroscopy and X-ray diff
raction. Both the diamond phase purity and growth rate are maximized w
ith 200 ppm N-2 in the gas mixture with further additions resulting in
reduced growth rates and poorer film quality. We explain these findin
gs in terms of the concentrations of gas phase species obtained from c
hemical equilibrium calculations and in particular the importance of t
he CN radical to the diamond growth process. (C) 1998 Elsevier Science
S.A.