Electron Affinity of the Bare and Hydrogen Covered Single Crystal Diamond (111) Surface

The electron affinity $\chi$ and the band diagram of single crystal diamond (111) surfaces was determined as a function of hydrogen coverage by combining work function measurements with photoelectron yield and core level photoemission spectroscopy. $\chi$ ranges from $-1.27\mathrm{}\mathrm{eV}$ for the fully hydrogen covered $(1\times 1)$ surface to $+0.38\mathrm{}\mathrm{eV}$ for the hydrogen free $(2\times 1)$ reconstructed surface. This change is quantitatively explained by a surface dipole model provided a coverage dependent depolarization is included. The dipole moment of the C-H bond on diamond (111) is found to be $0.09eÅ$.