High-resolution electron-energy-loss spectroscopic study of epitaxially grown diamond (111) and (100) surfaces

Abstract

Diamond (111) and (100) surfaces have been investigated by low-energy electron diffraction and high-resolution electron-energy-loss spectroscopy (HREELS). Samples were boron-doped semiconducting diamond surfaces grown homoepitaxially on natural diamond by microwave-plasma-assisted chemical-vapor deposition. A dipole-active C-H stretching vibration was observed at 352 meV (2839 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) on the (111) surface and 363 meV (2928 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) on the (100) surface. In the off-specular EELS spectra, two C-H stretching modes (352 and 361 meV) were clearly resolved on the (111) surface, while only one C-H stretching vibration was detected on the (100) surface. The two modes on the (111) surface are assigned to symmetric and asymmetric vibrations of ${\mathrm{CH}}_{3}$ species, respectively. This study clarifies hydrogen termination of the epitaxially grown diamond (111) and (100) surfaces in the forms of ${\mathrm{CH}}_{3}$ (methyl) and CH (monohydride) groups, respectively.