Surface electronic states of meteoritic nanodiamonds

Abstract

The C K edge of Orgueil nanodiamonds (C-delta diamonds) was acquired by electron energy-loss spectroscopy (EELS), with an energy resolution of 300 meV. The spectra show peaks at 282.5, 284.7, and 286.4 eV, which occur in the band gap below the main diamond edge and are absent from the bulk diamond spectrum. These peaks are attributed to transitions from degrees C 1s surface core levels to unoccupied surface states, and arise from single and pi-bonded dangling bonds and C-H bonds. A shoulder to the main absorption edge at 287.8 eV may correspond to hydrocarbon adsorbates. These results can be used to further our understanding of C-delta diamond structure and may reveal the presence of a fullerene-like surface. The unique surface electronic states of the C-delta diamond surfaces are expected to affect their optical properties, which are dependent on features such as extent of H coverage, particle size, and surface structure.