HIGH ELECTRONIC EXCITATIONS AND ION-BEAM MIXING EFFECTS IN HIGH-ENERGY ION-IRRADIATED FE SI MULTILAYERS/

Mossbauer spectroscopy (Fe-57) shows evidence for mixing effects induc ed by electronic energy deposition in nanoscale Fe/Si multilayers irra diated with swift heavy ions. A decrease in the mixing efficiency with electronic stopping power is reported; a threshold is found, under wh ich iron environment modifications no longer occur. The kinetics of Fe -Si phase formation after irradiation suggests the existence of three regimes: (i) for high excitation levels, a magnetic amorphous phase is formed directly in the wake of the incoming ion and an almost complet e mixing is reached at low fluence (10(13) U/cm(2)); (ii) for low exci tation levels, a paramagnetic Si-rich amorphous phase is favored at th e interface while crystalline iron subsists at high fluences; (iii) fo r intermediate excitation levels, saturation effects are observed and the formation rate of both magnetic and paramagnetic phases points to direct mixing in the ion wake but with a reduced track length in compa rison to U irradiation. The measured interfacial mixing cross section induced by electronic energy deposition suggests that a thermal diffus ion process is mainly involved in addition to damage creation. (C) Ame rican Institute of Physics.