This paper presents a rapid preparation of large amounts of ZnS nanowires and ZnS/ZnO heterostructure nanowires by chemical vapor deposition based on graphite reduction. The mixtures of ZnS and graphite powder with weight ratio of 3:1 were placed in a quartz boat, and the quartz boat was positioned at the center of a quartz tube furnace. A Si substrate coated with gold nanoparticles was placed at 5 cm downstream of carrying gas flow from ZnS source. Under a constant nitrogen flow rate of 100 sccm, the furnace was elevated to 870-935 °C at a pressure of 15-20 Torr. After reaction for 5-30 min, the Si substrate was taken out of the furnace after it was cooled down to room temperature, and the ZnS nanowires were grown on the substrate. Moreover, the superlattice and biaxial ZnS/ZnO heterostructure nanowires can be produced using the mixtures of ZnS, ZnO, and graphite with weight ratio of 1.5:1.5:1 as raw materials with a reaction temperature of 935-970 °C. The cable-like ZnS/ZnO heterostructure nanowires can be obtained by annealing the obtained ZnS nanowires in nitrogen at 700 °C for 2 h. The as-grown products have been characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence. The as-grown ZnS nanowires contain Wurtzite and Zinc blende structures, and the nanowires are tens of micrometers in length and 20-50 nm in diameter with high yield. To the best of our knowledge, it is the first report concerning the ZnO superstructure found in the as-gown biaxial ZnS/ZnO heterostructures. The HRTEM analysis shows ZB-ZnS(111) // ZnO(0001) in the superlattice heterojunctions and W-ZnS(0001) // ZnO(0001) in the cable-like heterojunctions. The three crystal planes are all polar planes, and they are parallel to each other in the ZnS/ZnO heterojunctions. The growth mechanism of ZnS and ZnS/ZnO heterostructure nanowires has been discussed. Their photoluminescence properties have been analyzed, and they all show broad green emission band.

Key words: ZnS, ZnO, Heterostructure nanowire, Growth mechanism, Interface