Control of ZnO nanorod array density by Zn supersaturation variation and effects on field emission

Abstract

We demonstrate control of ZnO nanorod density for self-organized growth on ZnO buffer layers on Si by varying Zn supersaturation during the initial growth phase, thereby altering the competition between 2D and 1D growth modes. Higher initial supersaturation favours nanorods of diameter <200 nm with micron-sized bases, resulting in low density nanorod arrays; nanorods grown with lower initial supersaturation have diameters <200 nm along their entire length, yielding higher density arrays. Field emission and imaging studies reveal field enhancement factors of >1000, attributed to sharp facet edges, and indicate that lower density arrays have more uniform emission due to a reduction in screening effects.