Direct verification of hydrogen termination of the semiconducting diamond(111) surface

Abstract

Low-energy, high-resolution electron energy loss spectroscopy has been used to identify the vibrational modes of hydrogen on the semiconducting diamond surface providing the first direct evidence that the (111) 1×1 surface is terminated by hydrogen. The vibrational loss spectrum from the ’’as-polished’’ surface shows two major losses near 160 meV (CH3 deformation), a major loss at 360 meV (CH3 stretch), and two minor losses at 520 and 720 meV (combinations and overtones). All of these losses disappear from the spectrum after heating the sample to ∠1000 °C (which has been established by other experiments to be sufficient to reconstruct the surface to 2×2/2×1). The loss spectrum for the reconstructed surface is indicative of a two-dimensional metallic state of the dangling-bond surface states for clean diamond. Exposure of this reconstructed surface to atomic hydrogen results in a loss spectrum which is essentially identical to that for the as-polished surface. Further verification that the loss spectrum results from hydrogen is provided by the shift of the structure to lower loss energies when deuterium is absorbed.