Adsorption and abstraction of hydrogen on polycrystalline diamond

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Abstract
The processes of atomic hydrogen adsorption and abstraction on a diamondsurface determine the fraction of sites available for reaction with carbon containing species during growth. The relative efficiencies of hydrogen atom adsorption and abstraction on a polycrystallinediamondsurface were determined at surface temperatures of 80 and 600 °C using high resolution electron energy loss spectroscopy. Abstraction is seen to occur 0.05 times as efficiently as adsorption on a diamondsurface at 80 °C. This is interpreted to indicate that the activation barrier to abstraction is higher than in analogous gas phase reactions. No change in either the adsorption or abstraction rate is seen for a diamondsurface at 600 °C indicating that hydrogen atoms do not accommodate the surface during the reaction. Thus, abstraction proceeds via a generalized Eley–Rideal mechanism.