Characterization of Ga-doped ZnO nanowires grown by thermal chemical vapor deposition

Ga-doped ZnO nanowire has a wurtzite hexagonal structure and has been prepared in a horizontal tube furnace by thermal chemical vapor deposition method . In this work, we fabricate the Ga-doped ZnO nanowires without a metalized catalyst through the thermal evaporation of the Zn powers and Ga metals at a low growth temperature of 550degC .Temperature is the critical experimental parameter for the formation of Ga-doped ZnO nanowires.This evaporation process can be attributed to the Ga dopant in the lattice position of he ZnO nanowires. As shown in scanning electron microscopy (SEM), nanowires of different diameters are evenly arranged on the Si substrate and nucleated via a self-catalysed mechanism by depositing a layer of ZnO film as the crystallization plant before growing ZnO nanowires on the film. Self-catalyzed growth of Ga-doped ZnO nanowires are of diameters 35-150 nm and lengths up to several ones of micrometers. High resolution Transmission electron microscope (HRTEM) lattice image of Ga doped ZnO nanowires, wherein those nanowires are seen a lattice of a=3.25 Aring and c=5.19 Aring. As determine by selected area diffraction (SAD), the growth direction of Ga-doped ZnO nanowires is [001] and the nanowire consists of single-crystalline ZnO crystals.The luminescence spectra of the Ga-doped ZnO nanowires exhibit a UV band at 374 nm and a strong green band at 498 nm. In addition, the Ga-doped ZnO nanowires with different diameters have a larger green light/UV ratio due to the recombination of holes with the electrons occupying the singly ionized more O vacancies that are larger in number. By virue of the doping of Ga, we observe that Ga-doped ZnO nanowires becomes broader and shifts to a longer wavelength 498 nm at a lower energy and a strong green emission as compared to the undoped one in the cathodoluminescence and photoluminescence spectra. The Ga-doped ZnO nanowires have a greater field-enhancement factor than the undoped ZnO nanowires. The Ga-doped ZnO nano- ires with a low turn on field (12 Vmum^-1) are apparently lower than the undoped ZnO nanowires. Our results demonstrate that Ga-doped ZnO nanowires can provide the possibility of application in optoelectric nanodevices.