The S_esensitivity of metals under swift-heavy-ion irradiation: a transient thermal process

Abstract

In the framework of the thermal-spike model the present paper deals with the effect of the electronic stopping power (Se) in metals irradiated by swift heavy ions. Using the strength of the electron-phonon coupling g(z) with the number of valence electrons z as the unique free parameter, the increment of lattice temperature induced by swift-heavy-ion irradiation is calculated. Choosing z=2, the calculated threshold of defect creation by Se for Ti, Zr, Co and Fe is about 11, 27.5, 28 and 41 keV nm-1, in good agreement with experiment. Taking the same z value, the calculation shows that Al, Cu, Nb and Ag are Se insensitive. Moreover, in Fe, the differences in the damage created by U ions of different energies but exhibiting the same value of Se may be interpreted by a velocity effect. Using z=2, other calculations suggest that Be (Se>or=11 keV nm-1), Ga (Se>or=5 keV nm-1) and Ni (Se>or=49 keV nm-1) should be sensitive to Se but Mg should not. These examples put the stress on the effect of the physical parameters governing the electron-phonon coupling constant apart from z determination: the sound velocity linked to the Debye temperature and the lattice thermal conductivity. Furthermore, a simple criterion is proposed in order to predict the Se sensitivity of metals.

Nanoporous SiO2/Si thin layers produced by ion track etching: Dependence on the ion energy and criterion for etchability

“…A͑r , t͒ is related to the kinetic energy of the projectiles thermalized in the electron system within about 10 −15 s. A͑r , t͒ is normalized to ensure that the integration in space and time is equal to the total energy loss S e . 34 The two differential equations are solved numerically as a function of space and time interval ͑dt͒, using the electronphonon coupling term g. 20,[34][35][36] The energy deposited on the electrons is followed assuming the known thermal conductivity. Via the specific heat, the difference in temperature between the electron and lattice subsystems ͓T e ͑r , t͒ − T a ͑r , t − dt͔͒ multiplied by ͑g ϫ dt͒ gives the part of the energy transferred to the atomic subsystem during dt.…”

Evidence for an Ultrafast Breakdown of the BeO Band Structure Due to Swift Argon and Xenon Ions

“…Under these conditions, perturbative mechanisms such as the site-specific Auger-induced ionic desorption [8] or collective mechanisms driven by high kinetic electron energies may gain importance. For the latter case, either lattice instabilities [9] or electronic thermal-spike effects [10,11] may play a major role, where hot electrons at electron temperatures of nearly 100 000 K [12,13] transfer their energy to the lattice.…”

Indications for Enhanced Auger-Electron Absorption in a Hot-Electron Gas

“…Using different Auger lines, these data yield snapshots of the time evolution of the solid a few 10 ÿ15 s after the rapid electronic excitation. Contrary to most lattice-modification studies, such investigations allow for a clear distinction of track-formation mechanisms [10].The pathways of the relaxation of high ionization densities inside solids and the formation of the so-called ion tracks have been the subject of a long-standing discussion [11,12]. During the past few years, however, it became obvious that the electronic thermal spike (atomic motion due to electron-atom collisions and electron-phonon couplings) plays a major role for the atomic rearrangement processes in metals and semiconductors [10,12].…”

“…The pathways of the relaxation of high ionization densities inside solids and the formation of the so-called ion tracks have been the subject of a long-standing discussion [11,12]. During the past few years, however, it became obvious that the electronic thermal spike (atomic motion due to electron-atom collisions and electron-phonon couplings) plays a major role for the atomic rearrangement processes in metals and semiconductors [10,12].…”

“…During the past few years, however, it became obvious that the electronic thermal spike (atomic motion due to electron-atom collisions and electron-phonon couplings) plays a major role for the atomic rearrangement processes in metals and semiconductors [10,12]. High electron temperatures, consistent with the populated electronic density of states (e-DOS) near the Fermi level [10,13,14], have been identified as a possible driving force of atomic motion.…”