Comparative study of the expansion dynamics of Ga‡ ions in the laser ablation of Ga and GaN using time-resolved extreme UV absorption spectroscopy

The expansion dynamics of Ga and GaN laser-ablation plumes were studied in vacuo using time-resolved extreme ultraviolet absorption spectroscopy. Targets of either Ga metal or pressed and sintered GaN pellets and a Nd-YAG laser (1.06 mm) at a ¯uence of 10 J cmÿ2 were used. Spatio-temporal maps of the relative concentration of Ga‡ are constructed by measuring the transmission through the ablation plumes of a pulsed beam of ultraviolet radiation tuned to 3p ! 3d inner-shell transitions in Ga‡. Marked differences between the Ga and GaN plumes were observed. The results are discussed in the context of the growth of GaN by Pulsed Laser Deposition (PLD). # 2000 Elsevier Science B.V. All rights reserved.