Atomization and Changes in Chemical Composition by Laser Ablation in Liquid prior to Determination of Trace Elements in Gallium Nitride.

Trace elements contained in single-crystal gallium nitride (GaN), which is a refractory material, were determined by inductively coupled plasma mass spectrometry with laser ablation in liquid (LAL) sampling. Particle size analysis by dynamic light scattering confirmed that LAL atomized the single-crystal GaN, and scanning electron microscopy/energy-dispersive X-ray spectrometry revealed that LAL sampling converted the GaN to gallium oxide particles. The atomization and changes in the chemical composition allowed for easy digestion of the sampled particles with nitric acid and a hot plate instead of with hydrochloric or sulfuric acid, a microwave digestion system, and a high-pressure vessel. Trace element analysis revealed the presence of trace Mg, Ge, Y, and Cd in single-crystal GaN, and the detection limits for these elements were 0.1 - 2 mg kg. The uncertainty derived from the small amount of sample used, which is a disadvantage of LAL sampling, was reduced by calculating the amount of sample ablated by measuring the concentration of the major element, Ga. We expect that the trace-element profiles of other refractory materials will be able to be determined by using this analytical approach.