No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

PACS : 61.46.+w; 81.16.Hc GaN nanowires were successfully grown on Ni-coated Si substrate by the direct reaction of gallium metal with ammonia gas in a home-made vertical tubular chemical vapor deposition reactor and characterized using field emission scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, and photoluminescence (PL) measurements. The growth of GaN nanowires was uniformly observed on the Si substrate surface when the distance between Ga and the Si substrate was in the range 0-4 cm. The diameter of the nanowires was about 25 nm, but the length was up to several micrometers. The clear lattice fringes in high-resolution TEM images revealed the growth of high-quality hexagonal single-crystal nanowires. PL of the GaN nanowires showed a strong band edge emission at an energy of $3.4 eV with negligible deep-level yellow emission. The catalytic growth mechanism of the GaN nanowires is discussed on the basis of the experimental results.

Absfrnct-ZnO nanostructures were synthesized at 5W°C over nickel catalyst supported on Si substrate in a homemade vertical chemical vapor deposition (CVD) reactor. The Z n O nanostructures had a needle-like morphology that the diameter of structures decreased linearly from the bottom to the top. The diameters of the Z n O nano-needles normally ranged from 20-100 nm and the lengths were in the range of 2-3 pm. The nanoneedles had a single wurtzite structure. The clear lattice fringes in HRTEM image also revealed the growth of good quality hexagonal single-crystal ZnO. The photoluminescence (PL) spectra of the nano-needles excited with a ultra-violet (UV) emission of 3.3 eV and a weak green emission at 2.4 eV at room temperature. Field emission characteristics of the ZnO nanowires showed that the turn-on field of ZnO nanowires was -6.10 V/pm with a lield enhancing factor p of -1099. The catalytic growth mechanism of the ZnO nanowires was discussed on the basis of experimental results in this work.