VITRIFICATION OF NON-METALLIC FILMS UNDER ENERGETIC ION BOMBARDMENT

The Segregation Charge Transfer (SCT) atomistic model is used to study phase nucleation in binary covalent films irradiated under conditions such that dense colllision cascades are formed along the ion trajectory. At the cascade-matrix interface a non-equilibrium compositional profile evolves, which is associated to a local electronic density profile. Relaxation to (meta)stable equilibrium is simulated by inter-atomic charge transfer reactions, involving dissimilar atoms, which result in the formation of an effective compound. The energy balance associated to electron transfer between two atoms, the absolute value of the percent enthalpy change at the formation of a molecule of effective compound, the percent variation of bonding ionicity degree and the absolute variation of component electronegativity differences in initial and effective compounds are calculated and compared. The analysis is performed on twenty-five compounds, among which thirteen were vitrified, while twelve remained crystalline under ion bombardment; qualitative differences in the parameter trends are found between the two families of systems.