Fourier transform infrared spectroscopy of C-H vibrational modes on a diamond (111) surface

A high-resolution analysis of the C-H stretching vibrational mode on single-crystal diamond (111)-(1 x 1):H using Fourier transform infrared spectroscopy (FTIR) is reported. The required surface sensitivity is achieved by utilizing multiple-internal-reflection infrared spectroscopy (MIRIRS) within a diamond prism. On the plasma-hydrogenated C(111) surface a sharp stretching mode at 2834.1 cm(-1) with a full-width at half-maximum (FWHM) of 1.9 cm(-1) is observed which is selectively excited in p-polarization only. With increasing temperature this mode is broadened and shifted towards lower energies following Persson's dephasing mechanism [B.N.J. Persson, R. Ryberg, Phys. Rev. B 40 (1989) 10273]. A second, broader component at 2834.8 cm(-1) (FWHM=6.5 cm(-1)) is assigned to C-H bonds near steps, edges, defects etc. The hydrogen termination of the diamond (111) surface could be removed by annealing in ambient air at 400 degrees C for 6 h. This unusual low desorption temperature is interpreted in terms of an oxygen-assisted desorption mechanism. (C) 2000 Elsevier Science S.A. All rights reserved.