Ab initiocalculation of electron affinities of diamond surfaces

The electron affinity (EA) of various terminations of diamond surfaces has been calculated by the ab initio pseudopotential method. The bare, reconstructed (100) and (111) surfaces are found to have positive EA’s of 0.5 and 0.35 eV, respectively. The hydrogen-terminated surfaces $1\times 1\left(100\right):2\mathrm{}\mathrm{H}$, $2\times 1\left(100\right):\mathrm{H}$, and (111):H have sizable negative EA’s of order $-$2.4, $-$2.0, and $-$2.0 eV, respectively. A symmetrical canting was found to be the most stable geometry for the $1\times 1\left(100\right):2\mathrm{}\mathrm{H}$ surface. The oxygen-terminated surfaces have positive affinities of +2.6 eV for the more stable ether configuration, while the OH termination has a negative EA. The various values can be understood in terms of the surface dipole of the terminating bond.