Growth and optical properties of ZnO nanorods prepared through hydrothermal growth followed by chemical vapor deposition

Very well aligned vertical ZnO nanorods with high optical quality were successfully synthesized by sequentially employing an aqueous solution method on a ZnO seed layer and a thermal chemical vapor deposition (CVD). The process is growing the upper ZnO nanorods by using CVD on top of the bottom nanorods synthesized by using an aqueous solution method on a Si substrate with a ZnO seed layer. These double-structured-nanorods showed a significant improvement of optical quality. The CVD re-grown upper nanorods showed orders-of-magnitude enhancement of the band edge emission and complete compression of the deep level emissions, compared with the solution-grown bottom nanorods. By comparing emission spectra from the series of samples with and without the seed layer or the second CVD growth, we can conclude that the improvement can only be achieved by combining the CVD, the solution-based synthesis technique, and the seed layer.