Growth and TEM characterization of GaN microcrystals using a Ni catalyst

High-quality GaN microcrystals were grown by direct reaction of gallium and ammonia using a Ni-mesh catalyst. The catalytic activity markably increased the growth yield of the GaN microcrystals. The average grain size of the GaN microcrystals synthesized in the presence of the Ni catalyst was larger than of the microcrystals synthesized that in the absence-of the catalyst. It was thought that the Ni-mesh catalyst accelerated the decomposition of NH3 gas into chemically active nitrogen atom while it reduced the activation energy for the reaction of gallium with NH3. The characterization of the catalytically grown GaN microcrystals using transmission electron microscopy and X-ray and/or electron diffraction patterns showed that the hexagonally shaped GaN rods with their c-axis along the length of the single crystal were dislocation free. The growth mechanism of GaN micro-crystals is discussed based on the experimental observation.