The CH stretching features on diamonds of different origins

Surface CH stretching features on diamonds from various sources have been explored using Fourier transform infrared spectroscopy and Raman spectroscopy. The exploration encompasses the samples of natural, meteoritic, and synthetic diamond crystallites produced by high-pressure/high temperature, and detonation methods. To obtain the infrared spectra, the diamond samples are first surface-cleaned by oxidation and then hydrogenated using atomic hydrogen created by hot tungsten filaments under vacuum. Sharp and distinct features, corresponding to the CH stretch of tertiary C on C(111)-1 x 1, are observed at 2835 cm(-1) for samples of different origins, but the peak shape depends on the surface morphology. For meteoritic and detonation-synthesized diamonds, however, the 2835 cm(-1) peak is completely missing. We attribute this observation to a domain size effect, where the sizes of the C(111)-1 x 1 facets created on these two diamond samples (3 and 5 nm in diameter, respectively) by H-etching are too small to yield the characteristic CH stretching feature. This study gives a detail analysis on the IR spectra of the CH stretching feature on various diamond and diamond films. (c) 2005 Elsevier B.V. All rights reserved.