Laser Ablation

Laser ablation is a method of nanowire synthesis that is able to synthesize GaN nanowires through ablation of a mixture of GaN and Ga2O3 powders in a 3:1 molar ratio. Similar to VLS, the powders are placed in a heated and pressurized furnace with a temperature of 900 C and a working pressure of 400 Torr. A 248 nm, 10 Hz laser was then pulsed onto the powders for a total period of 2 hours. This created a large amount of GaN nanowires. This is known as the “oxide-assisted growth mechanism” [3], in which a series of oxidation and reduction reactions between the initial GaN and Ga2O3 powders form nucleation sites when exposed to the laser.

Compared to VLS, this synthesis takes a larger period of time as well without replacing expensive equipment or reagents. Though the chemical reagents are different from the feed gases found in VLS, the process itself still requires a contained furnace with both high heat and pressure, similar to VLS. The actual nanowires obtained from the process are not very specific, as they range from diameters of 20 to 120 nm. Their lengths are a few micrometers as well, which results in entanglement of the nanowires. When observed under HRTEM, the same lattice spacing and intersection angles were observed when compared to GaN nanowires synthesized using VLS. [3]