Controllable Synthesis of Zn<sub><em>x</em></sub>Cd<sub>1-<em>x</em></sub>S Nanowires with Tunable Optical Properties

Abstract

ZnxCd1-xS (0<x<1) nanowires with several different compositions were successfully synthesized on Si wafers by a simple vapor deposition method using Au as a catalyst. The morphology and composition of the nanowires were investigated by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results show that the Zn/Cd ratio is controllable by adjusting the relative amount of the starting materials and the deposition temperature. The Xray diffraction patterns show that the nanowires are single crystals with the wurtzite structure. The morphology character of the nanowires suggests that the growth of the nanowires can be explained by the base-growth mechanism. The optical characteristics of the nanowires were studied by Raman and photoluminescence (PL) spectroscopy. Raman shifts of the longitudinal optical (LO) phonon mode were observed in the ZnxCd1xS nanowires. The LO peak frequency changed smoothly with changing composition, which approximately shows a one-mode behavior pattern in the ZnxCd1xS nanowires. In the PL spectra, both band-gap and defect emission were observed. The PL results indicate that the emission frequency originating from the band-gap transition of the ZnxCd1xS nanowires can be tuned through modulating of the composition. The band-gap of the nanowires can be tuned from 2.41 eV (CdS) to 3.63 eV (ZnS). 576 LIN Xu-Feng et al.: Controllable Synthesis of ZnxCd1-xS Nanowires with Tunable Optical Properties No.3