Surface electronic states of the partially hydrogenated diamond C(100)-(2X1): H surface - art. no. 165421

Surface electronic states of the partially hydrogenated diamond C(L00)-(2x1 ):H surface were studied by near-edge x-ray absorption fine structure and C 1s core level photoemission. Partially hydrogenated surfaces were prepared by synchrotron irradiation of the monohydride-terminated surface or by hyd rogen adsorption on the clean surface. A new surface core-exciton state pro duced at a photon energy of 282.5 eV has been assigned to single dangling b onds of the partially hydrogenated surface. Monitoring this new feature has been found to be a powerful method to study hydrogen kinetics during (i) p hoton irradiation of a fully hydrogenated diamond surface, (ii) adsorption of atomic hydrogen on a clean diamond surface, and (iii) photon irradiation of a fully hydrogenated surface followed by thermal annealing. From the an alysis of dangling-bond distribution, it follows that no preferential pairi ng of hydrogen on the C-C dimers occurs during hydrogen adsorption at room temperature. In contrast, thermal annealing induces pairing of the single d angling bonds into the pi -bonded configuration, the pairing process being accompanied by hydrogen desorption. This observation suggests that the acti vation barrier of hydrogen thermal diffusion is only slightly lower than th at of thermal desorption.