GROWTH PHENOMENON IN AMORPHOUS SOLIDS IRRADIATED WITH GEV HEAVY-IONS - ELECTRONIC-ENERGY-LOSS DEPENDENCE OF THE INITIAL GROWTH-RATE

Electronic excitation (dE/dx)(e) due to swift-heavy-ion irradiation in duces giant plastic deformation in amorphous solids. In situ electrica l resistance experiments performed on Fe-B ribbons irradiated with dif ferent tilting angles with respect to the ion beam provide quantitativ e information about the deformation phenomenon. In particular, dimensi onal variations occurring in the early stages of the process can be ev aluated. At medium (dE/dx)(e) (irradiation with Xe ions) the growth st arts with a zero rate within experimental uncertainties, whereas an in itial nonzero rate is observed at high (dE/dx)(e) (irradiation with Pb or U ions). Results are discussed in light of a recent model based on irradiation-induced thermal spikes.