ADSORPTION AND ABSTRACTION OF HYDROGEN ON POLYCRYSTALLINE DIAMOND

The processes of atomic hydrogen adsorption and abstraction on a diamond surface 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 polycrystalline. diamond surface were determined at surface temperatures Of 80 and 600 degrees C using high resolution electron energy loss spectroscopy.: Abstraction is seen to occur:0.05;,times as efficiently as adsorption on a diamond surface at 80 degrees 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 diamond surface at 600 degrees C indicating that hydrogen atoms do not accommodate the surface during the reaction. Thus, abstraction proceeds via a generalized Eley-Rideal mechanism.