Pulsed laser ablation of dense sintered AlN and AlN powder samples studied by time-of-¯ight mass spectroscopy

The response of tape-casted polycrystalline dense sintered AlN wafers and uniaxial densi®ed AlN powder pellets to pulsed laser radiation (pulse length 7 ns FWHM) is studied at energy ¯uences over the ablation threshold. The pulse energy is varied between 64 and 1400 mJ/cm2 at wavelengths between 250 and 1000 nm. The ablation yield is quanti®ed by a quadruple mass spectrometer. Dense sintered AlN samples show a linear response upto 400 mJ/cm2 while at ¯uences over 400 mJ/cm2 a saturation of the ablation yield is noticeable. AlN powder samples, on the other hand, do not show this saturation. Moreover, the total ablation yield on powder samples is signi®cantly higher. These observations supplemented by secondary electron microscopy images have been discussed in terms of sample composition, surface metallization, and ablation plume formation. # 2001 Elsevier Science B.V. All rights reserved