The prediction of phases in ion beam mixed multilayers

Abstract

The prediction of the alloy phases resulting from the ion beam mixing of multilayered thin film structures made significant progresses with the clear understanding of the physical nature of the thermal spikes, the formulation of the thermodynamics and kinetics of phase transformation under ion bombardment and the introduction of the concept of effective heat of mixing for thin film binary systems. The present paper shows that the stage of knowledge achieved on these aspects allows to predict the phases that will be formed during the ion beam mixing of one specific multilayered binary system under different bombardment conditions. Examples from the literature for metal-metal multilayers submitted to ion beam mixing are discussed here. A more detailed discussion for the multilayered FeAl system with varying Fe and Al thicknesses in order to cover most of the concentration intervals is also presented. The Fe/Al multilayers were submitted to both thermal annealing in high vacuum and ion beam mixing with different ionic species and substrate temperatures. In all these cases the phases predicted on the basis of the approaches here outlined agree with those observed experimentally, as well as the phase sequences following the first phase formation.