Luminescent properties of ZnO nanorod Arrays grown on Al:ZnO buffer layer

Well-aligned ZnO nanorod arrays were synthesized noncatalytically on a conducting aluminum-doped zinc oxide (AZO) buffer layer. The synthesis uses no metal catalyst and is cost-effective. The buffer layer facilitates the growth of vertically aligned nanorods; furthermore, we demonstrate that the optical properties of the resulting nanorods are closely correlated to the crystallographic quality of the buffer layer. Spatially resolved cathodoluminescence microscopy measurements show that for nonideal buffer layers the optical quality of nanorods improves along the [0001] direction leading to a lower defect incorporation at the nanorod tip. We have minimized defect incorporation by proper adjustment of the buffer layer growth. In addition, the ZnO nanorods grown from our best AZO buffer layer show improved alignment perpendicular to the substrate and a narrower diameter distribution. Our results suggest that the quality of the buffer layer and the growth conditions are key parameters to optimize the nanorods' optical properties.