A Mössbauer study on the ion-beam-induced phases in the Fe/Al thin film bilayer

Abstract

Conversion Electron Mössbauer Spectroscopy, (CEMS), has been used to study ion-beam-induced mass transport and phase formation in the Fe/Al bilayer system. In a previous work it was shown that ion irradiation in the same system with noble gases (Ar⁺, Kr²⁺, and Xe³⁺) leaded to the formation of non intermetallic phases when the samples were kept at 77 and 300 K during the bombardments. On the other hand, intermetallic phases were observed for irradiations at substrate temperature of 500 K. The last experimental condition for phase formation corresponds to a lower temperature than conventional thermal treatment needs to reach the same phase. Here, the irradiation conditions were devised to account intermediate substrate temperatures, namely 200 and 400 K, in order to identify the effect of the implantation dose in the phase formation. The intermetallic phases observed in the samples submitted to irradiations at substrate temperature of 500 K, are now formed by even lower temperature-400 K. The results also show a threshold dose of irradiation above which the intermetallic phases are formed. These observations are discussed in terms of a superposition of collision cascades.