Direct growth of quasi-aligned ultrafine ZnS nanowire arrays on conducting zinc foils and their field emission properties.

Quasi-aligned ultrafine ZnS nanowire arrays have been grown directly on zinc substrates via a simple hydrothermal method. The morphology, structure, and composition are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The single-crystalline ultrafine ZnS nanowires have a hexagonal structure with typical diameters of 5-15 nm and lengths of up to micrometers. A possible growth mechanism is proposed. Since the Zn foil serves as both the Zn source and substrate, direct synthesis and assembly of ZnS nanowires on an electrically conductive Zn substrate are accomplished in one step. Optical properties of the product are studied by photoluminescence. Field emission measurements disclose that the synthesized nanostructures possess good electron emission properties with a low turn-on field of about 5.4 V/microm at a current density of 10 microA/cm2. The materials are potentially useful as cathode materials in field emission devices.