Structure and growth mechanism of quasi-aligned GaN layer-built nanotowers

Quasi-aligned GaN layer-built nanotowers on silicon (111) substrates by employing ultrathin Ni catalyst films have been grown at 800°C in a metal-organic chemical vapor deposition system. The nanotower size and the degree of alignment were found to be highly sensitive to changes in the Ni catalyst film thickness. The several growth stages of nanotowers were examined by microscopic technique, which indicates the variation in surface morphology from Ni islands to hexagonal prismatic GaN particles, and finally to GaN layer-built nanotowers. For the third stage, the growth may be attributed to an asymmetric and step by step copying process.