Abstract
Vertically aligned undoped ZnO and Sb-doped ZnO nanowires have been synthesized on a silicon substrate using the vapor-solid technique, without using a catalyst or predeposited buffer layers. The structure and morphology of the as-synthesized nanowires are characterized using X-ray diffraction, scanning and transmission electron microscopies, selected area electron diffraction, and electron dispersive X-ray spectroscopy. The results showed that the use of Si(111) is a critical factor for the growth of vertically aligned nanowires. This is a result of the lattice match on Si(111), which is more favorable with the ZnO lattice structure because the Si(111) surface is hexagonal and has a smaller lattice constant of 3.840 angstrom. The photoluminescence properties were also investigated at room temperature (300 K). The UV peaks of undoped and Sb-doped ZnO nanowires are located at 3.33 and 3.29 eV, respectively. This redshift of 0.04 eV in the Sb-doped ZnO indicates a reduction of the ZnO band gap caused by the Sb dopant. The temperature-dependent photoluminescence spectra of Sb-doped ZnO nanowires from 10 to 300 K were also examined. This measurement showed that at 10 K several peaks appear, at 3.36, 3.23 and 3.04 eV, which were assigned as acceptor-bound excitons, a donor-acceptor pair and a zinc-vacancy-related peak, respectively. These peaks are shifted with the increase of temperature up to 300 K.