ZnO nanowires doped with a high concentration Ga, In, and Sn were synthesized via thermal evaporation. The doping content defined as X/(Zn + X) atomic ratio, where X is the doped element, is about 15% for all nanowires. The nanowires consist of single-crystalline wurtzite ZnO crystal, and the average diameter is 80 nm. The growth direction of vertically aligned Ga-doped nanowires is [001], while that of randomly tilted In- and Sn-doped nanowires is [010]. A correlation between the growth direction and the vertical alignment has been suggested. The broaden X-ray diffraction peaks indicate the lattice distortion caused by the doping, and the broadening is most significant in the case of Sn doping. The absorption and photoluminescence of Sn-doped ZnO nanowires shift to the lower energy region than those of In- and Ga-doped nanowires, probably due to the larger charge density of Sn.

Novel Zn1-xMnxSe one-dimensional nanostructures-straight nanowires (x = 0.1 and 0.3), zigzagged nanobelts (x = 0.4), and toothed nanosaws (x = 0.4)-were synthesized using the chemical vapor deposition method. They all consisted of single-crystalline wurtzite ZnSe crystals, irrespective of the Mn content. In particular, the nanosaws have a unique structure in which double-sided teeth are rooted in the nanowire core and bent so as to align as two parallel rows. The long axis is parallel to the [010] direction, and all of the teeth have the [0001] growth direction. The X-ray diffraction pattern confirms the formation of wurtzite ZnSe crystal and the decrease of the lattice constant owing to Mn doping. The Mn2+ emission at 2.1 eV (appeared below 100 K), originating from the d-d (4T1 --> 6A1) transition, proves the effective substitution of Mn2+ ions at the tetrahedral coordinate sites.

Comparative Structure and Optical Properties of Ga-, In-, and Sn-Doped ZnO Nanowires Synthesized via Thermal Evaporation. -High-density undoped and Ga-, In-, and Sn-doped ZnO nanowires are prepared on Si substrates coated with Au nanoparticles via thermal evaporation at 500-1000°C. The samples are characterized by SEM, TEM, XPS, XRD, UV/VIS, photoluminescene, and catodoluminescence spectroscopy. The absorption and photoluminescence of Sn-doped ZnO nanowires shift to the lower energy region than those of In-and Ga-doped nanowires, probably due to larger charge density of Sn. It is suggested that the charge density of the doped element would be an important parameter in controlling the optical properties of ZnO nanowires. -(BAE, S. Y.; NA, C. W.; KANG, J. H.; PARK*, J.; J.