Interpenetrative and transverse growth process of self-catalyzed ZnO nanorods

Beside longitudinal growth along the length, we show that ZnO nanorods also exhibit transverse growth, which is responsible for the formation of interpenetrative nanorods. The longitudinal growth is lead by the catalytically active Zn-terminated (0001) surface, while the oxygen-terminated (0001¯) surface is catalytically inactive, resulting in the formation of 'pencil' or 'bullet' shaped nanostructures.