The electron affinity (EA) $\chi$ of single crystal diamond (100) is determined as a function of hydrogen and oxygen coverage by a combination of work function and photoemission experiments. For the fully hydrogenated (100)-$(2\mathrm{}\times 1):\mathrm{H}$ surface an EA of $-1.3\hspace{0.5em}\mathrm{eV}$ and for the oxidized surface C(100)-$(1\mathrm{}\times 1):\mathrm{O}$ $\chi =+1.7\mathrm{}\hspace{0.5em}\mathrm{eV}$ are obtained. These are the lowest and the highest electron affinities, respectively, ever reported for any diamond surface. The variation in $\chi$ with O and H coverage is well described by a simple dipole model provided that the depolarization is properly taken into account for high adsorbate densities. This analysis favors the bridge position (etherlike) for oxygen on C(100). By mixing H and O adsorbates on a microscopic scale the EA of C(100) can be adjusted at will over 3 eV between the extreme values without jeopardizing the chemical passivation of the diamond surface afforded by H or O termination.

• Received 3 May 2001

DOI:https://doi.org/10.1103/PhysRevB.64.165411