Laser-Assisted Synthesis of Amorphous/Pseudoamorphous GaN Thin Films and Nanostructures
Amorphous/pseudoamorphous GaN was prepared by pulsed-laser ablation at room temperature without any heat treatment. The structure and chemical composition of the specimens were systematically investigated. Laser ablation at low Ar pressure (<50Pa) led to deposition of smooth Ga-rich films, which is independent with laser energy. Under same pressures, as laser energy increased, the film stoichiometry changed from Ga-rich to near stoichiometric composition. Varying background Ar pressure strongly affected the product structure showing little effect on the chemical composition. Under higher pressure than 100 Pa, fine nanoparticles with a size of 5 nm rather than films were deposited on substrate due to the increased collision by plume confining. The optical band-gap of the deposited a-GaN is 2.8 eV for thin films and 3.9 eV for nanoparticles.
T. Ohji, T. Sekino and K. Niihara
S. H. Shim, N. Koshizaki, J. W. Yoon, K. B. Shim, "Laser-Assisted Synthesis of Amorphous/Pseudoamorphous GaN Thin Films and Nanostructures", Key Engineering Materials, Vols. 317-318, pp. 585-588, 2006