The growth of epitaxial Ge nanowires is investigated on (100), (111) B and (110) GaAs substrates in the growth temperature range from 300 to 380 °C. Unlike epitaxial Ge nanowires on Ge or Si substrates, Ge nanowires on GaAs substrates grow predominantly along the [Formula: see text] direction. Using this unique property, vertical [Formula: see text] Ge nanowires epitaxially grown on GaAs(110) surface are realized. In addition, these Ge nanowires exhibit minimal tapering and uniform diameters, regardless of growth temperatures, which is an advantageous property for device applications. Ge nanowires growing along the [Formula: see text] directions are particularly attractive candidates for forming nanobridge devices on conventional (100) surfaces.

Sn-catalyzed CdS nanowires were grown by a physical vapor transport method by using tin sulfide as a precursor. The bimodal distribution consisting of tall/thin and short/thick nanowires is found at the growth temperatures of 250–350 °C. The tall/thin nanowires grow along ⟨0001⟩ while the short/thick nanowires grow along ⟨011̅0⟩ and all have wurtzite crystal structure. The relationships, valid in the wide range 25–150 nm in nanowire diameters, of d c = (2.64 ± 0.08)d NW for the tall/thin nanowires and of d c = (1.27 ± 0.02)d NW for the short/thick nanowires, are obtained where d c and d NW are the diameters of catalyst and nanowire, respectively. Using nucleation theory, we calculate that the energies of nucleation are quite similar for both types of nanowires, which may explain the bimodality. Both types of nanowires show prominent photoluminescence without any noticeable trace of impurity-related bands, indicating their high optical quality.

We have investigated the growth of ternary CdSSe nanostructures by physical vapor transport, specifically aiming at the synthesis of CdSSe nanosheets. CdSSe nanostructures with various S mole fractions are grown at growth temperatures less than 800 degrees C and photoluminescence from these nanostructures covers the entire visible spectral range. Morphological evolution from nanowires to nanosheets is observed as increasing growth temperatures due to the change of relative dominance in the growth mechanism from vapor-liquid-solid to vapor-solid. Nanosheets whose widths extend several tens of micrometers are successfully synthesized. However, nanosheets show a strong suppression effect of S incorporation when the growth is dominated by the vapor-solid mechanism. A micro-photoluminescence study shows high optical quality of individual CdSSe nanostructures with polarization anisotropy ratios rho ~ 0.1. In addition, lateral heterostructure CdS/CdSe nanosheets are successfully synthesized by two step growth. Strong red and green emissions are observed by selective laser excitations focusing at the center and edge parts of these heterostructure nanosheets, respectively. These heterostructure CdS/CdSe nanosheets may be useful for multicolor light emitting devices.

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