Effects of Au catalysts for synthesis of ZnS microstructures on the sapphire substrate

In this paper, microsaws and microtowers have been prepared by vapor–liquid–solid (VLS) and vapor–solid (VS) methods, respectively, which are based on thermal evaporation. The role of Au catalyst in defining the morphology of the ZnS microstructures has been found. The microsaws were synthesized onto the sapphire substrate in the presence of Au catalyst, and the microtowers were produced onto Au-uncoated sapphire substrate. The microstructural changes were studied through a scanning electron microscope. The structural characterization of the microstructures was indicated by X-ray diffraction and a high-resolution transmission electron microscope. Room temperature photoluminescence measurements with 325 nm excitation showed four emission bands located at ∼400 nm, ∼480 nm, ∼520 nm and ∼580 nm.

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► Microsaws and microtowers were synthesized onto Au-coated and Au-uncoated sapphire substrate, respectively, as shown in Fig. 1(a, b).
► Without Au catalysts, the high intensity of diffraction peaks reveals the growth direction along the [001] direction, as shown in Fig. 1c.
► New yellow emission band at 580 nm was observed for both the ZnS microtowers and microsaws.