Gallium nitride (GaN) nanocrystals were grown on the surface of single-wall carbon nanotube (SWCNT) bundles using the molecular beam epitaxial technique. A single-source precursor of GaN combined with NH3 was used for the growth of GaN nanocrystals in the substrate temperatures of 550–700 °C. Over this temperature range, the nanometre-sized granular GaN crystallites were favored in the initial nucleation and growth. However, in the temperature range between 625 and 675 °C, spearhead-shaped nanorods grew radially out of the SWCNTs. This directional growth is explained by a steric hindrance-driven growth originating from the nano-size of the SWCNT substrate. The growth was facilitated by the catalytic dissociation of NH3 in Ga metal droplets that formed at the nanorod tips. The structure was investigated by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and Raman spectroscopy. The field-emission property of the hybrid structure was also measured for possible application.
