Self-assembly of well-aligned gallium-doped zinc oxide nanorods

Highly oriented Ga-doped ZnO nanorod arrays have been fabricated on GaN and sapphire substrates by pulsed laser deposition. X-ray diffraction shows that these nanorods are grown epitaxially with the c-axis normal to the substrate. The ZnO nanorod formation proceeds as follows. After a wetting layer of ZnO film grows to approximately 14 nm in thickness, the Stranski–Krastanov instability takes place due to interface strain. As a result, ZnO nanodots are formed uniformly on the ZnO layer. These nanodots then serve as nucleation sites for the subsequent electric-field-assisted growth of nanorods. Ga-doping level plays a key role in the formation of ZnO nanorods, while the oxygen partial pressure and the substrate temperature also affect the morphology of nanorods. These self-assembled and ordered ZnO nanorod arrays may be used in field emission and optoelectronic applications.