THE SILICON/GERMANIUM (111) INTERFACE : THE ONSET OF EPITAXY

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Carbon 1 s studies of diamond(111): Surface shifts, hydrogenation, and electron escape lenaths

As probed by photoemission, the valence band emission spectra of diamond(lll) undergo reversible changes due to cycles of hydrogen adsorption and desorption. We report here carbon Is spectra from diamond(111) as a function of hydrogen exposure-annealing cycles and as a function of photon energy. We find an additional shoulder to lower binding energy in the C Is spectra of the hydrogen-free reconstructed 2 X 2/2 X1 surface and interpret this result as due to a chemical shift (0.95 \uc2\ub10.1 eV) of the surface atoms. We analyze the data in terms of models for reconstruction and also derive the inelastic scattering length (escape length) of electrons in diamond over the kinetic energy range 25\ue2\u80\u931000 eV

Banksia species (Proteaceae) from severely phosphorus-impoverished soils exhibit extremem efficiency in the use and re-mobilization of phosphorus

Banksia species (Proteaceae) occur on some of the most phosphorus (P)-impoverished soils in the world. We hypothesized that Banksia spp. maximize P-use efficiency through high photosynthetic P-use efficiency, long leaf lifespan (P residence time), effective P re-mobilization from senescing leaves, and maximizing seed P concentration. Field and glasshouse experiments were conducted to quantify P-use efficiency in nine Banksia species. Leaf P concentrations for all species were extremely low (0.14–0.32 mg P g−1 DM) compared with leaf P in other species reported and low relative to other plant nutrients in Banksia spp.; however, moderately high rates of photosynthesis (13.8–21.7 µmol CO2 m−2 s−1), were measured. Some of the Banksia spp. had greater P proficiency (i.e. final P concentration in senesced leaves after re-mobilization; range: 27–196 µg P g−1 DM) than values reported for any other species in the literature. Seeds exhibited significantly higher P concentrations (6.6–12.2 mg P g−1 DM) than leaves, and species that sprout after fire (‘re-sprouters’) had significantly greater seed mass and P content than species that are killed by fire and regenerate from seed (‘seeders’). Seeds contained only small amounts of polyphosphate (between 1.3 and 6 µg g−1 DM), and this was not correlated with P concentration or fire response. Based on the evidence in the present study, we conclude that Banksia species are highly efficient in their use of P, explaining, in part, their success on P-impoverished soils, with little variation between species.Matthew D. Denton, Erik J. Veneklaas, Florian M. Freimoser and Hans Lamber

Diamond (111) surface: a dilemma resolved

A dilemma due to the experimental observation of a 'clean' unreconstructed elemental semiconductor surface without band gap states is resolved. Results from photon stimulated ion description, high resolution low energy electron loss spectroscopy and photoemission spectroscopy find that the conventionally polished diamond (111) 1 multiplied by 1 surface is atomically terminated and electronically stabilized by hydrogen. Thermal desorption of hydrogen upon heating results in a reconstructed 2 multiplied by 2/2 multiplied by 1 surface with filled electronic surface states in and near the fundamental gap. Exposure of the reconstructed surface to atomic hydrogen (or dueterium) is found to again terminate the surface and remove the near band gap surface states. Apparent inconsistencies in the understanding of the diamond: hydrogen interaction are resolved