Black-coloured GaN nanoparticles with an average grain size of 50nm were obtained by annealing GaN nanoparticles under flowing nitrogen at 1200C for 0.5h. XRD measurement result indicated an increase in the lattice parameter of the GaN nanoparticles annealed at 1200C, and HRTEM image showed that the increase could not be ascribed to other ions in the interstitial positions. If the as-synthesised GaN nanoparticles at 950C were regarded as standard, the thermal expansion changed non-linearly with temperature and was anisotropic; the expansion below 1000C was smaller than that above 1000C. This study provided an experimental demonstration for selecting the proper annealing temperature of GaN. In addition, a large blue-shift in optical band-gap of the annealed GaN nanoparticles at 1200C was observed, which could be ascribed to the dominant transitions from the C(Γ7) with the peak energy at 3.532eV.

Effect of High Temperature Annealing on Strain and Band Gap of GaN Nanoparticles. H.D.Xiao, H.Z.Mao, Z.J.Lin, H.L.Ma: Chinese Physics B, 2010, 19[8], 086106