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.

Time-resolved optical techniques are used to explore electron spin dynamics in bulk and epilayer samples of n-type ZnO as a function of temperature and magnetic field. The bulk sample yields a spin coherence time T * 2 of 20 ns at T = 30 K. Epilayer samples, grown by pulsed laser deposition, show a maximum T * 2 of 2 ns at T = 10 K, with spin precession persisting up to T = 280 K.A lot of attention has been focused on zinc oxide (ZnO) because of material properties that make it well-suited for applications in ultra-violet light emitters, transparent high-power electronics and piezoelectric transducers. In addition, the theoretical work of Dietl et al ., 1 predicting room temperature ferromagnetism for Mn-doped p-type ZnO, has revealed the possibility that ZnO may be an appropriate candidate for spintronics. 2 The magnetic properties of thin films of ZnO with transition ion doping, 3,4,5 are being widely investigated, but practical spintronics applications would also require long spin coherence time and spin coherence length.

High-density ZnO nanowires doped with 4 atom % sulfur (S) and pure ZnO nanowires were grown vertically aligned on a silicon substrate. They were synthesized via chemical vapor deposition of a Zn or Zn/S powder mixture at 500 °C. The S-doped ZnO nanowires usually form bundles. The average diameter of the S-doped ZnO nanowires and ZnO nanowires is 20 and 50 nm, respectively. They consist of single-crystalline wurtzite ZnO crystals with a uniform growth direction of [001]. Elemental mapping reveals that the S doping takes place mainly at the surface of the nanowires with a thickness of a few nanometers. X-ray diffraction data suggest that the incorporation of S would expand the lattice constants of ZnO. The photoluminescence and cathodoluminescence of S-doped ZnO nanowires exhibit a significantly enhanced green emission band that comes from the S-doped surface region of the nanowires.

High-density ZnO nanorods can be grown on pregrown one-dimensional nanostructures via thermal chemical vapor deposition of Zn at a low temperature of 500 °C, producing various heterostructures. We demonstrate it using carbon nanotubes, GaN nanowires, GaP nanowires, SiC nanowires, and SiC core-C shell coaxial nanocables. The diameter of ZnO nanorods is in the range of 80-150 nm, and the maximum length is about 3 µm. The ZnO nanorods align vertically on the walls of 1D nanostructures, with a uniform growth direction of [001]. We suggest a vapor-liquid-solid growth mechanism that Zn vapor deposits on the 1D nanostructures and produces the outer layers encapsulating the 1D nanostructures; the ZnO nanorods are grown out from the outer layers of the nanocable structure. The length and density of ZnO nanorods are controllable by the deposition time. All of these heterostructures exhibit intense UV photoluminescence and cathodoluminescence. The green emission intensity is correlated with the density of the ZnO nanorods.