INTERACTION OF ATOMIC-HYDROGEN WITH THE DIAMOND C(111) SURFACE STUDIED BY INFRARED-VISIBLE SUM-FREQUENCY-GENERATION SPECTROSCOPY

Atomic hydrogen (deuterium) adsorbed onto the diamond C(111) surface h as been studied by infrared-visible sum-frequency-generation spectrosc opy. Monohydride termination of H/C(111) is confirmed by the observati on of sharp CH stretch (2838 cm(-1)) and CH bend (1331 cm(-1)) modes i n the spectrum. Deuterium on the surface gives a CD stretch frequency of 2115 cm(-1). The rate of hydrogen adsorption is measured in compari son with the rate of deuterium abstraction by hydrogen. Measurement of thermal desorption of hydrogen from C(111) suggests a near first-orde r desorption kinetics with an activation energy of 4.0+/-0.4 eV and a preexponential factor of 10(15+/-2) s(-1). On the bare reconstructed C (111) surface, distinct CC surface phonon features characteristic of t he (2X1)-reconstructed surface are seen, which seem to support the mod ified Pandey model of Bechstedt and Reichardt.