The impact of gas isotopic exchange on the growth rate and hydrogen (deuterium) bonding within CVD diamond films

Diamond films were grown by hot filament chemical vapor deposition (HF CVD) technique using isotopic gas mixtures: CH4 + H2 and CD4 + D2 with a constant ratio of 1%:99%. The influence of isotopic exchange on the growth kinetics and film properties was investigated. The microstructure and phase composition of regular and isotopic diamond films have been investigated by high resolution scanning electron microscopy (HR‐SEM) and Raman spectroscopy, respectively. The C–H and C–D vibration modes in the film bulk and surface region were studied by Raman spectroscopy and high resolution electron energy loss spectroscopy (HR‐EELS), correspondingly. It was found, that the exchange of H by D atoms in CH4 and H2 gases reduces the diamond growth rate by a factor of 2.3 and improves the film quality. The microstructure of diamond films of comparable thicknesses was found to be very similar for diamond films grown from two different gas mixtures. The HREEL and Raman spectra of these films show the same C–H/D vibrations modes with isotopic shift. We suggest that the rate‐controlling step in the growth process is the disassociation of C–D or C–H bond on the diamond surface and that the isotopic exchange influences the kinetics of diamond growth, but not its mechanism. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)