Laser Assisted Catalytic Growth of ZnS/CdSe Core-Shell and Wire-Coil Nanowire Heterostructures

Abstract

ZnS/CdSe core-shell and wire-coil nanowire heterostructures have been synthesized by chemical vapor deposition assisted with pulsed laser ablation. Measurements from high-resolution transmission electron microscopy and selected area electron diffraction have revealed that both ZnS/CdSe core-shell and wire-coil nanowires are of single-crystalline hexagonal wurtzite structures and grow along the [0001] direction. While the lattice parameters of ZnS and CdSe in the core-shell nanowires are nearly equal to those of bulk ZnS and CdSe, change of the lattice parameters in the CdSe-coil is attributed to the doping of Zn into CdSe, resulting in the relaxation of compressive strain at the interface between CdSe-coil and ZnS-wire. Composition variation across the interfacial regions in the ZnS/CdSe nanowire heterostructures ranges only 10-15 nm despite the pronounced lattice mismatch between ZnS and CdSe by~11%. Growth mechanisms of the ZnS/CdSe nanowire heterostructures are discussed.