Optical and microstructural characterization of chemically synthesized gallium nitride nanopowders

Thermal decomposition of an amido precursor; [Ga₂(NMe₂)₆, Me = CH₃] in an ammonia atmosphere yielded nanostructured gallium nitride powder. The x-ray diffraction spectrum of the nanosized gallium nitride exhibited reflections corresponding to the lattice planes of fcc (zinc blende) GaN. High resolution transmission electron microscopy confirmed the cubic structure of the material and evidence of stacking faults within the fcc structure. Infrared spectra showed the characteristic Ga-N stretch at 550 cm^-1. Transmission electron microscope measurements indicated that the GaN consisted of ≈50 nm sized particles which in turn are agglomerates of smaller particles with ≈5 nm domain sizes. The photoluminescence (PL) emission spectrum of the GaN was found to be sensitive to the excitation wavelength exhibiting peaks at 378 and 317 nm. The PL excitation spectrum showed resonances in the 200-300 nm region. These PL results suggest the effect of quantum confinement in these GaN particles.