Molecular oxygen adsorption on partially hydrogenated diamond (100) surfaces

Molecular oxygen has been found to be easily adsorbed on the partially hydrogenated diamond $C(100)-(2×1):H$ surfaces, whereas the clean and fully hydrogenated C(100) surfaces are completely inert to molecular oxygen. The partially hydrogenated diamond $C(100)-(2×1)$ surfaces have been prepared by (i) in situ hydrogen photodesorption from the fully hydrogenated surface and (ii) in situ hydrogen adsorption on the clean surface. The surface reactivity has been monitored through the changes of the valence band photoemission spectra upon molecular oxygen exposure. These results suggest that oxygen adsorption occurs on the isolated carbon dangling bonds produced, on partially hydrogenated surfaces, from the breaking of the $π$-bonding of paired dangling bonds.