Interaction of atomic hydrogen with the diamond C(111) surface studied by infrared-visible sum-frequency-generation spectroscopy

Abstract

Atomic hydrogen (deuterium) adsorbed onto the diamond C(111) surface has been studied by infrared-visible sum-frequency-generation spectroscopy. Monohydride termination of H/C(111) is confirmed by the observation of sharp CH stretch (2838 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) and CH bend (1331 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) modes in the spectrum. Deuterium on the surface gives a CD stretch frequency of 2115 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. The rate of hydrogen adsorption is measured in comparison with the rate of deuterium abstraction by hydrogen. Measurement of thermal desorption of hydrogen from C(111) suggests a near first-order desorption kinetics with an activation energy of 4.0\ifmmode\pm\else\textpm\fi{}0.4 eV and a preexponential factor of ${10}^{15\ifmmode\pm\else\textpm\fi{}2}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$. On the bare reconstructed C(111) surface, distinct CC surface phonon features characteristic of the (2\ifmmode\times\else\texttimes\fi{}1)-reconstructed surface are seen, which seem to support the modified Pandey model of Bechstedt and Reichardt.