The carbon $1s$ core levels of diamond (100) and (111) surfaces were investigated using high-resolution photoelectron spectroscopy. The surfaces were prepared in a hydrogen plasma, which is known to result in atomically flat surfaces. From the signature of the C $1s$ core-level spectra, four different surface terminations can be distinguished. The as-prepared surfaces exhibit a surface component shifted by $+0.5\mathrm{}$ to $+0.8\mathrm{}\mathrm{eV}$ toward higher binding energy, which we assign to multiple termination of carbon atoms by hydrogen. Annealing these surfaces first results in the development of the surfaces terminated monoatomically by hydrogen. A small chemical shift of $-0.15\mathrm{eV}$ was deduced for the hydrogen-terminated surface atoms of the (111):H surface with respect to the bulk carbon atoms. Further annealing leads to spectra characteristic for hydrogen-free, reconstructed diamond surfaces. This process is shown to be thermally activated with an activation energy of $3.4\pm 0.4\mathrm{eV}.$ The corresponding chemical shifts between surface and bulk components vary between $-0.78$ and $-1.15\mathrm{eV}$ depending on surface orientation and surface treatment. Finally, annealing at $T\approx 1250°\mathrm{C}$ leads to a partially graphitized surface for diamond (111) while on the diamond (100) surface a $4\times 1$ reconstruction is observed. The sign and magnitudes of the chemical shifts are discussed.

• Received 24 October 1997

DOI:https://doi.org/10.1103/PhysRevB.57.12397