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 et al., "Laser-Assisted Synthesis of Amorphous/Pseudoamorphous GaN Thin Films and Nanostructures", Key Engineering Materials, Vols. 317-318, pp. 585-588, 2006