ZnS nanowaveguides with rectangular cross-section (∼50 × 50 nm 2 ) and tens of microns in length have been synthesized by pulsed laser vaporization of ZnS/10% Au targets in a flow of Ar/5% H 2 . The highly crystalline filaments exhibit the wurtzite structure, growing mainly along the [001] or [100] directions. Photoluminescence at room temperature shows strong near-edge luminescence doublets (∼3.75 eV and 3.68 eV) and a weak defect luminescence structure attributed to stoichiometric defects and possibly to Au impurities. Optical absorption (OA) at room temperature shows a strong broadening of the fundamental direct absorption edge identified with stoichoimetric defects. Two peaks (3.75 and 3.85 eV) in the OA are also observed. We believe that the structure in the photoluminescence and optical absorption (3.68, 3.75, 3.85 eV) are from direct transitions between the conduction band and the spin−orbit/crystal field splitting of the valance bands. Theoretical results are also presented that show the size-dependence of the band gap in ZnS nanowires.

The effects of Si doping on the evolution of stress in AlxGa1−xN:Si thin films (x≈0.4–0.6) grown on 6H-SiC by metal organic chemical vapor deposition were investigated using in situ wafer curvature measurements. The results were correlated with changes in film microstructure as observed by transmission electron microscopy. The incorporation of Si into the films resulted in a compressive-to-tensile transition in the biaxial stress at the surface, and the magnitude of the tensile stress was found to increase in proportion to the Si concentration. The stress gradient was attributed to Si-induced dislocation inclination resulting from an effective climb mechanism. Si doping also resulted in a decrease in the threading dislocation density in the AlxGa1−xN layers, which was attributed to increased dislocation interaction and annihilation. The model describing tensile stress generated by dislocation effective climb was modified to account for the dislocation reduction and was found to yield an improved fit to the experimental stress-thickness data.

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