VITRIFICATION PROCESSES UNDER ENERGETIC ION-BOMBARDMENT

The features of the atomistic segregation-charge transfer (SCT) model needed to explain phase nucleation in binary alloy films, bombarded un der conditions such that dense collision cascades develop, are outline d. A non-equilibrium compositional profile evolves at each cascade-mat rix interface, due to segregation at the interface of one of the film components. Such a local stoichiometry change is associated with the d evelopment of an electronic density profile, which can be non-equilibr ium over the typical timescale for cascade quenching. Relaxation to (m eta)stable equilibrium occurs via charge transfer reactions, which giv e rise to the formation of dimers of an effective compound. The amount of energy required to introduce an effective alloy dimer into the mat rix is calculated and the surface and thermochemical properties of the initial and effective alloys are compared. The model is applied to th e analysis of 21 alloys, out of which 10 were amorphized by ion beams, and qualitative differences are found between the systems undergoing amorphization and crystalline phase formation. (C) 1998 Elsevier Scien ce B.V. All rights reserved.