Synthesis and optical properties of well-aligned ZnS nanowires on Si substrate

An organic-assistant chemical vapor transport and condensation method is introduced to synthesize well-aligned ZnS nanowires. By means of decomposition of organics, a risen flow is generated that drives the ZnS nanowires growth direction upwards. From SEM images, the diameters of nanowires are uniform and nanowires are well-aligned and vertical to the surface of the silicon substrate. XRD pattern, TEM image and SAED suggest that the structure of ZnS nanowires is hexagonal and single crystalline. The growth orientation of nanowires is toward 〈0 0 2〉. In RAMAN spectrum, the E₁ (LO) mode resulting from the lateral morphology of ZnS nanowires is also observed in our sample. It restricts the phonon propagation direction to parallel the c-axis. A blue-light emission band is revealed in the PL spectrum which can be attributed to vacancies and surface states.