Synthesis and optical properties of ZnO–ZnS core-shell nanotube arrays

Abstract

Heterostructured ZnO–ZnS core-shell nanotube arrays with the diameters of 50–80nm and lengths up to 1μm were synthesized by a two-step chemical reaction. First, the ZnO layer was grown by atomic-layer deposition. It was found that the preferred growth orientation was strongly dependent on the substrate temperature. After sulfuration conversion from arrayed ZnO nanorods, the ZnS–ZnO composite arrays can be successfully prepared, as evidenced from transmission electron microscopy. This confirms that the ZnO–ZnS core-shell nanotube-arrayed structure has been fabricated. X-ray photoelectron spectroscopy analysis indicates that the binding energy of S 2p is the same as that of bulk single-crystal ZnS and that the Zn 2p3∕2 peak is shifted about 0.5eV due to the formation of Zn–S bonds. Photoluminescence shows the relative-intensity ratio of ultraviolet emission (IUV) to deep-level emission (IDLE) for ZnO∕ZnS core-shell nanotubes can be enhanced to be nine times that of original ZnO nanotubes.