THE S(E) SENSITIVITY OF METALS UNDER SWIFT-HEAVY-ION IRRADIATION - A TRANSIENT THERMAL-PROCESS

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 S(e) 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 S(e) insensitive. Moreover, in Fe, the differences in the damage created by U ions of different energies but exhibiting the same value of S(e) may be interpreted by a velocity effect. Using z = 2, other calculations suggest that Be (S(e) greater-than-or-equal-to 11 keV nm-1), Ga (S(e) greater-than-or-equal-to 5 keV nm-1) and Ni (S(e) greater-than-or-equal-to 49 keV nm-1) should be sensitive to S(e) 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 S(e) sensitivity of metals.