Laser induced desorption and ablation: mechanism of metal removal from an Al-Cu-Fe alloy and a quasicrystal of the same composition

摘要

Quasicrystals are a special class of metallic alloys that share some of the properties of crystals.Their structures reduce to a single repeating unit like that of the unit cell of a crystal. The quasi-unitcellis representative of a cluster like structure where electrons cannot move with freedom as in metals.Quasicrystals are formed of metallicelements but they do not have metallic properties.The diversity of the fractionation behavior induced by laser desorption and ablation of theAl70Cu20Fe10of the intermetallicalloy and of theAl65Cu23Fe12quasicrystal has been examined in terms of the structuralproperties of the two compounds. Elemental fractionation during laser desorption and ablation samplingwas investigated by using inductively coupled plasma mass spectrometry. The experiments were carried outin two different irradiance regimes by a Nd-YAG laser with 266 nm wavelength and single 6 nanosecond laserpulses. In the high irradiance regime(>0.04, 0.07GW/cm2)the effect of the laser irradiance is not discriminating.In the low irradiance regime(<0.04, 0.07GW/cm2)large differences have been found between thealloy and the quasicrystal. The results have been interpreted on the basis of a thermodynamic vaporizationprocess for the intermetallic alloy. An electronic model of localized excitation is suggested for the physicalprocess of surface material removal from a quasicrystal.