Gallium nitride quantum dots in a nitrogen-bonded silica gel matrix

Abstract

GaN:SiO2 nanocomposites were successfully synthesized by a two-step process. Firstly, an intermediate xerogel was obtained by the sol-gel method and, in the second step, annealing the powdered samples at 900 degrees C for 5 h in flowing NH3 atmosphere produced the nanocomposites. X-ray diffraction and high-resolution transmission electron microscopic studies confirmed that the confined GaN nanoparticles (2-12 nm) were crystallized as a mixture of hexagonal and cubic phases. The optical band gap was observed to be enhanced slightly (3.69 eV) from the bulk value (3.39 eV) for the sample with the lowest molar ratio of GaN (10: 90) in the nanocomposites. Fourier transform infrared spectroscopic studies indicated the formation of Ga-N bond along with probable signatures of Si-O, Si-N and Si-N-O bonds. The nanocomposites showed photoluminescence peaks at 370 and 571 nm as a result of excitation at 310 nm. Raman study of the samples shows peaks corresponding to the hexagonal and cubic phases of GaN.