It is found that an ordered and air-stable GaAs͑111͒A-͑1ϫ1͒-Cl surface can be produced by chemical etching/passivation with dilute HCl solution. The synchrotron polarization-dependent Cl K-edge x-ray absorption near-edge structure and x-ray photoelectron spectroscopy studies showed that the surface is terminated with Ga-Cl bonds oriented along the surface normal. Low-energy electron diffraction studies showed a bulklike ͑1ϫ1͒ structure on the Cl-terminated GaAs͑111͒A surface. The Cl termination eliminates surface band-gap states caused by surface oxides. Photoluminescence measurements showed a dramatic increase in the near-band radiative emission rate corresponding to reduction in the occupied surface band-gap states. A reduction of surface gap states by Cl termination was confirmed by surface photovoltage measurements.

Photoluminescence properties of self-assembled InAs quantum dots grown on InP substrates by solid source molecular beam epitaxy

The influence of (NH4)2S treatment on the surface properties of GaP is presented for the first time. Changes in the chemical composition and Fermi level position are characterized using X-ray photoelectron spectroscopy. These measurements show that after surface treatment, the GaP surface is free of native oxides. A strong enhancement (~ 50 times) in the cathodoluminescent efficiency was observed for sulfur passivated samples. Schottky diode characteristics were used to reveal changes in the barrier height and interface state density due to surface treatment. Changes in carrier concentration were also found to be reflected in measured Raman spectra. The passivation mechanism is also briefly discussed.

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-We report on the preparation of lead oxides nanostructured thin films by anodic and cathodic electrochemical deposition. The films were prepared using an aqueous electrolyte composed of lead chloride and nitric acid, without any catalyst. A controlled potential was applied through the electrolyte to deposit the lead oxide on gold coated silicon and on titanium foil. The formation of lead oxide nanostructures was strongly influenced by the applied potential, deposition temperature and solution pH. The role of these parameters on the synthesis of nanostructured lead dioxide was studied in detail, and enabled the determination of the optimal conditions for the fabrication of nanostructured lead dioxide thin films suitable for wastewater treatment.