Pulsed laser ablation and deposition of quasicrystals

The gaseous phase obtained by ablating a quasicrystalline AlCuFe target by nanosecond, piceosecond and femtosecond lasers, has been characterized by different techniques such as emission spectroscopy, quadrupole mass spectroscopy and ICCD imaging with the aim to study the plume composition, energy and morphology. To clarify the ablation process some films have been deposited, on oriented silicon, at different experimental conditions and analyzed by scanning electron microscopy, atomic force microscopy, energy dispersive x-ray analysis and x-ray diffraction. The results from nanosecond ablation show evidence of distinct albation mechanisms, which lead to different gas phase composition, as a function of the laser fluence. Films containing the quasicrystalline phase can be deposited only at fluences higher than about 6.5 J cm-2 while at lower fluences the aluminum content exceeds the stoichoimetric values. The results obtained from femtosecond and picosecond ablation show that the processes in the short pulse regimes ar very different to the nanosecond one. In particular the plume angular distribution shows a characteristic high cosine exponent and the composition of the deposits is completely stoichiometric and independent from the laser fluence, even if to obtain quasicrystalline films a substrate temperature of 600°C is needed.