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. Targ ets of either Ga metal or pressed and sintered GaN pellets and a Nd-YAG las er (1.06 mum) at a fluence of 10 J cm(-2) were used. Spatio-temporal maps o f the relative concentration of Ga+ an constructed by measuring the transmi ssion through the ablation plumes of a pulsed beam of ultraviolet radiation tuned to 3p --> 3d inner-shell transitions in Ga+. Marked differences betw een the Ga and GaN plumes were observed. The results are discussed in the c ontext of the growth of GaN by Pulsed Laser Deposition (PLD). (C) 2000 Else vier Science B.V. All nights reserved.