Symmetric and asymmetric growth of ZnO hierarchical nanostructures: nanocombs andtheir optical properties

Abstract

One-dimensional nanostructure growth behaves very differently on the ± (0001) polar surfaces of wurtzite ZnO, resulting in asymmetric growth in these two directions. Inthis report we show that by tuning the degree of supersaturation, the growth asymmetrycan either be rationally utilized or broken to obtain single- or double-sided ZnO nanocombs,respectively. The nanowires grown on the two polar surfaces of the double-sided nanocombsare of comparable length, suggesting some kind of symmetric growth, but they aredistributed on the two sides in an asymmetric manner. More interestingly, the two sides ofthe double-sided nanocomb exhibit distinct optical properties. Possible mechanisms areproposed to explain the growth and optical properties of the double-sided nanocombs.