Catalyst Free Vapour-Solid Growth of Novel GaN Nanostructures at Low Temperature

We report the role of a double stage heat treatment process for the synthesis of novel GaN nanostructures (NSs) using a two stage furnace following a catalyst free vapour solid growth mechanism. Morphological analysis revealed that GaN NSs were composed of rod-like structures with average diameter of 250 nm and accumulated particulates of GaN with diameter of similar to 12-16 nm providing enhanced surface area, which will be important when GaN is used as a catalyst support. The wurtzite phase of GaN nanorods of agglomerated nanoclusters was synthesized at temperatures as low as 750 degrees C. An X-ray photoelectron spectroscopic study confirmed formation of GaN. The surface areas of the GaN NSs were high at similar to 20 m(2)/g with respect to that expected for solid nanorod structures. The GaN NSs were of high crystallinity and purity as revealed by structural studies. Raman spectral analysis showed stronger intensity of the A(1) (LO) mode with respect to that for E-2(high) mode indicating the good electronic quality of the sample. A photoluminescence study revealed the dominant presence of a defect band around 1.7-2.1 eV corresponding to nitrogen di-vacancies. Subsequent annealing in NH3 has demonstrated a compensation of the defect state and evolution of band edge peak with possible hydrogen compensation of surface states.