Pulsed laser ablation of dense sintered AlN and AlN powder samples studiedby time-of-flight mass spectroscopy

The response of tape-casted polycrystalline dense sintered AlN wafers and u niaxial densified AIN powder pellets to pulsed laser radiation (pulse lengt h 7 ns FWHM) is studied at energy fluences over the ablation threshold. The pulse energy is varied between 64 and 1400 mJ/cm(2) at wavelengths between 250 and 1000 nm. The ablation yield is quantified by a quadruple mass spec trometer. Dense sintered AlN samples show a linear response upto 400 mJ/cm( 2) while at fluences over 400 mJ/cm(2) a saturation of the ablation yield i s noticeable. AlN powder samples, on the other hand, do not show this satur ation. Moreover, the total ablation yield on powder samples is significantl y higher. These observations supplemented by secondary electron microscopy images have been discussed in terms of sample composition, surface metalliz ation, and ablation plume formation. (C) 2001 Elsevier Science B.V. All rig hts reserved.