Swift Heavy Ion Irradiation on Quasicrystals
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Swift Heavy Ion Ir r adiation on Quasicr ystals Ratnamala Chatterjee Physics Depar tmen t, I ndian Institute of Technol ogy (Delhi), Hauz Khas, New-Delhi 110016, INDIA
ABS TRACT The present level of understanding of the effects of irradiation of quasicrystalline targets with swift heavy ions has been reviewed here. The results of systematic deposition of large amount of energy densities (12 keV/nm < (dE/dx)e < 40 keV/nm) in Al-Cu-Fe based system are discussed in terms of resistivity measurements (in-situ measurements of resistivity changes with increasing flux (ions/cm2) and ex-situ resistivity vs temperature measurements before and after irradiation) & standard and high-resolution X-ray diffraction measurements made before and after irradiation. The studies are aimed at understanding the changes that may occur in these alloys as a result of the relaxation of such highly excited states of matter. Also, we attempt to learn whether such changes are typical to the long-range quasicrystallinity of the system or not. INTRODUCTION ‘Interaction of energetic ion-beams with solid’ is a subject that has interested the scientific community. The exact results of the effect of irradiation depend on the velocity regime, energy and charge of the incoming ions and the particular ion-target combination that is used. In the ‘low-velocity regime’ elastic collisions dominate and the energy is directly transferred to the target atoms. The effect of such irradiation depends on the diffusion properties of the defects created by irradiation and of the implanted species themselves. On the other hand in the ‘highvelocity regime’, inelastic collisions leading to the excitation of target electrons dominate. The effect of this kind of irradiation is mainly determined by the efficiency of the energy transfer (i.e. the densities of energy deposition) from the target electrons to the target lattice. In this paper we review the present level of understanding of the effects of irradiation of ‘high-velocity’ ions on the quasicrystalline targets. The work started [1] in 1993 with the swift heavy-ion irradiation on metastable Ti-Ni quasicrystalline sample. Since then various reports on a“ s prepared” and w “ ellannealed” stable Al-Cu-Fe quasicr ystalline system in both bulk [2 – 5] and thin-film [6,7] forms have been reported. The aim of such a study is two-fold: (i) To investigate how efficiently the excited electrons can transfer the deposited energy in stable quasicrystalline systems that are known to have very low densities of state at the Fermi energy; and to learn whether or not there exists a threshold (dE/dx)e (electronic energy deposition per unit length) of projectiles that can induce permanent structural changes in these systems. The results fill the gap in the literature of swift heavy ion (SHI) irradiation on metallic alloys. Various studies [8,9] are available on the effect of SHI on crystalline or amorphous metals/ metallic alloys. Its effect on the quasicrystalline form of metallic alloys, that is believed to be a state in bet
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