A new modulated structure with a superlattice (a = 2.209nm, b = 3.826nm, c = 1.037nm, α = β = γ = 90°) was found in nanoparticles which had been synthesized by using a direct-current arc plasma method. The nanoparticles transformed into particles, with holes at their centers, under electron-beam irradiation during high-resolution electron microscopy. Meanwhile, Ga atoms were extruded onto the surfaces of the nanoparticles and formed an amorphous layer. Simulations of high-resolution images and electron diffraction patterns revealed that the modulation could be attributed to the aggregation of N vacancies which were created during electron irradiation. Molecular dynamics calculations showed that the aggregation of N vacancies was far more energetically favourable than was that of Ga vacancies.

A New Modulated Structure in GaN Nanoparticles. H.Li, H.P.Sun, F.Shen, Z.Zhang: Philosophical Magazine Letters, 2002, 82[2], 91-8