Structure and optical properties of cored wurtzite (Zn,Mg)O heteroepitaxial nanowires

The synthesis, structure, and optical properties of one-dimensional heteroepitaxial cored (Zn,Mg)O semiconductor nanowires grown by a catalyst-driven molecular beam epitaxy technique are discussed. The structures form spontaneously in a Zn, Mg and O-2/O-3 flux, consisting of a single crystal, Zn-rich Zn1-xMgxO(x<0.02) core encased by an epitaxial Zn1-yMgyO(y>0.02) sheath. High resolution Z-contrast scanning transmission electron microscopy shows core diameters as small as 4 nm. The cored structure forms spontaneously under constant flux due to a bimodal growth mechanism in which the core forms via bulk like vapor-liquid-solid growth, while the outer sheath grows as a heteroepitaxial layer. Temperature-dependent photoluminescence shows a slight blueshift in the near band edge peak, which is attributed to a few percent Mg doping in the nanoscale ZnO core. The catalyst-driven molecular beam epitaxy technique provides for site-specific nanorod growth on arbitrary substrates. (C) 2004 American Institute of Physics.