A high-resolution analysis of the C-H stretching vibrational mode on single-crystal diamond (111)-(1×1):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-1with a full-width at half-maximum (FWHM) of 1.9 cm-1is 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. 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 °C for 6 h. This unusual low desorption temperature is interpreted in terms of an oxygen-assisted desorption mechanism.
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