Mass-transport driven by atomic displacement and ballistic relocation effects under ion irradiation

Ion bombardment-induced atomic redistribution processes in the initially homogeneous multi-components and multilayered structures is analysed considering a relocation function, which defines the frequency probability of relocation between monolayers and kinetic equations which describe the evolution of distribution profiles of components. The heterogeneous distribution of atomic displacement rate between neighbouring monolayers initiates a flux of atoms driven out of the region with maximum nuclear energy losses and the relaxation flux that is introduced to satisfy the packing condition, balances the ballistic flux in steady state. The presented equations for a two-element target are consistent with ones obtained considering the redistribution of components under ion bombardment used in the Sigmund approach. However, it significantly simplifies calculations and can be easily modified to include the simultaneous action of adsorption, preferential sputtering, cascade mixing, diffusion and resorption for multi-component targets and multilayers. The calculated results are compared with experimental microprofiles induced by ion bombardment.