The Raman spectrum of gallium oxide ͑␤-Ga 2 O 3 ͒ nanowires with ͓001͔ growth direction is identical to that of the bulk Ga 2 O 3 ͓Y. C. Choi et al. Adv. Mater. 12, 746 ͑2000͔͒ while that of ␤-Ga 2 O 3 nanowires with ͓401͔ growth direction is redshifted by 4-23 cm −1 ͓Y. H. Gao et al. Appl. Phys. Lett. 81, 2267 ͑2002͔͒. Here we report the Raman and Fourier transform infrared spectra of ␤-Ga 2 O 3 nanowires with ͓110͔ growth direction which is blueshifted relative to the bulk spectra by ϳ10-40 cm −1. Based on a first principles calculation of the strain dependence of Raman mode frequencies in bulk ␤-Ga 2 O 3 , we correlate the observed frequency shifts to growthdirection-induced internal strains in the nanowires.

We explore the combined effects of phonon confinement and local heating caused by laser beam absorption on the Raman spectra of Germanium nanowires of different diameters ͑6 nm, 7 nm, and 12 nm͒. The asymmetric broadening and downshifting of the first order Raman band is studied as a function of the average wire diameter and the local temperature of the nanowires. The basic phenomenological model with a modified confinement function incorporated with thermal effects is in good agreement with our experimental results. We also show the effects of the nanowire diameter, thermal conductivity of the underlying substrate, and the mediating substance ͑gallium in this case͒ on the local temperature of the nanowires.

the air hole array of a triangular lattice in an alumina matrix. For the formation of a fluorescent-dye layer on the surface of porous alumina, the porous alumina substrate was dipped in an ethanol solution containing 20 wt.-% dendrimer [13] and 4 × 10 -3 M pyrromethene 597 (EXITON) for 1 min and then dried. The thickness of the fluorescent-dye layer was approximately 1 lm.Optically pumped lasing experiments were performed using a frequency doubled Nd 3+ :yttrium aluminum garnet (YAG) pulse laser (532 nm wavelength, 8 ns pulse width, and 10 Hz repetition rate). The spot size of the incident light was 300 lm. The excitation light from the laser was irradiated from a direction parallel to the cylinder array to the surface of the fluorescent-dye layer. The emission from the cross section of porous alumina cut in the C-X direction was observed using a spectrometer.

Synthesis of nanowires of Group III antimonides (GaSb and InSb) is studied in detail using two approaches: (i) direct antimonidization of Group III metal droplets and (ii) reactive vapor transport of Group III metals in the presence of antimony in the vapor phase. The diameter of the GaSb nanowires ranged from 30 to 700 nm and length from a few to hundreds of micrometers. GaSb nanowires as long as 1 millimeter have been synthesized using direct antimonidization of large (several millimeters) sized gallium droplets. Reactive vapor transport of Group III metals in the presence of antimony in the vapor phase led to the formation of homoepitaxially oriented GaSb nanowire arrays on top of GaSb crystals. In the case of InSb, 100-nm-thick nanowires were obtained by direct antimonidization of indium droplets. Optical and electrical measurements of the GaSb nanowires, performed using photoluminescence and scanning tunneling spectroscopy, reveal a band gap of ∼0.72 eV, similar to that of bulk GaSb.