Surface electronic states of the partially hydrogenated diamondC(100)−(2×1):Hsurface

Abstract

Surface electronic states of the partially hydrogenated diamond C(100)-(2ϫ1):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 hydrogen adsorption on the clean surface. A new surface core-exciton state produced at a photon energy of 282.5 eV has been assigned to single dangling bonds of the partially hydrogenated surface. Monitoring this new feature has been found to be a powerful method to study hydrogen kinetics during ͑i͒ photon irradiation of a fully hydrogenated diamond surface, ͑ii͒ adsorption of atomic hydrogen on a clean diamond surface, and ͑iii͒ photon irradiation of a fully hydrogenated surface followed by thermal annealing. From the analysis of dangling-bond distribution, it follows that no preferential pairing of hydrogen on the C-C dimers occurs during hydrogen adsorption at room temperature. In contrast, thermal annealing induces pairing of the single dangling bonds into the -bonded configuration, the pairing process being accompanied by hydrogen desorption. This observation suggests that the activation barrier of hydrogen thermal diffusion is only slightly lower than that of thermal desorption.

Combining nanostructuration with boron doping to alter sub band gap acceptor states in diamond materials

“…Such carbon atoms have dangling bonds and are predominantly found at partially or non hydrogenated surfaces typical to grain boundaries leading to unoccupied states within the valence band. 60 Glans et al further proposed that localized states on these C atoms result in feature A. 43 This furthermore validates the observation of surface excitonic states in case of the B:Dfoam-O.…”

Interaction of Thermally Activated and Molecular Oxygen with Hydrogenated and Hydrogen-Free Diamond Film Surfaces: Chemical Reactivity and Electron Emission Properties

“…On the other hand, this surface is reactive to thermally activated oxygen gas. Moreover, oxygen atoms are chemisorbed, as revealed from the PSID, showing structures characteristical to chemically bonded surface oxygen, and XPS measurements displaying the shift of the C (1s) peak to a higher binding energy, which is characteristic to the change of the oxidation state of carbon [24,28]. Let us to consider several reaction passes, which may take place.…”

Structural change induced in carbon materials by electronic excitations

“…The most pronounced change in the XAS-TEY spectra is the distinct growth of π * peak [2], and that in the XAS-FL spectra is the development of a new peak at 283 eV below the π * peak. The former represents the increase of graphitic structures and the latter is possibly attributed to the generation of dangling bonds in tetrahedral coordinations [22]. Figure 2(a) shows the efficiency of the structural change quantified per soft X-ray photons absorbed by the sample.…”

“…For the experiments at SPring-8, a sample was introduced in a ultra-high vacuum chamber evacuated to 3×10 -7 Pa to be exposed to nearly monochromatic soft X-rays near the C 1s core edge from a figure-8 undulator beam line 27SU [21]. Intense illumination was achieved at a flux intensity as high as 10 22 photons/s·m 2 in the energy range of 240 eV to 310 eV with an energy width of 7 eV. The structural change caused by the intense illumination was examined by X-ray absorption spectra (XAS) acquired in the total electron yield (TEY: electronic current flowing out of the sample) mode with a higher energy resolution of 0.1 eV before and after the intense illumination.…”