Investigation of hydrogen incorporation in CVD diamond films using infrared reflection spectroscopy

Abstract

In this work hydrogen incorporation in CVD diamond films of different quality has been assessed using infrared reflection and absorption spectroscopy. Infra red (IR) reflection spectra, taken from the rough growth surfaces of as-grown polycrystalline diamond films, show a well-defined two-phonon absorption intrinsic feature and different CH stretching bands depending on the quality of the film, and are similar to the corresponding transmission spectra. While IR reflection spectra taken from the smooth interfaces of the as-grown films show only weak absorption in the diamond two-phonon region and no visible CH stretching band, although the reflectance is much higher than that of the growth surfaces. This marked difference between the spectra taken from the growth surfaces and backsides of the films cannot be explained in terms of surface roughness, and is discussed on the base of the columnar growth of CVD diamond film and compared with SIMS and ERDA data in the literature. Our reflection results can not be explained using the model of hydrogen terminated at grain boundaries and evidence that the CH stretching band is associated with the intrinsic diamond two-phonon lattice absorption, which strongly indicates that infrared-active hydrogen is bonded to bulk diamond carbon atoms.