High-resolution surface-sensitive C1score-level spectra of clean and hydrogen-terminated diamond (100) and (111) surfaces

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 $+0.5$ to +0.8eV 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 -0.15eV 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±0.4eV. The corresponding chemical shifts between surface and bulk components vary between -0.78 and -1.15eV depending on surface orientation and surface treatment. Finally, annealing at T≈1250^∘C leads to a partially graphitized surface for diamond (111) while on the diamond (100) surface a 4×1 reconstruction is observed. The sign and magnitudes of the chemical shifts are discussed.