Defects and energy accommodation in epitaxial sputter deposited Mo/W superlattices studied by molecular dynamics

We report here the results of a Molecular Dynamics—Embedded Atom Method—investigation of the pathways generating point defects in Mo/W superlattices during bombardment with energetic (50 to 200 eV) Ar and Kr neutrals. Energy accommodation coefficients are computed for the different structures and are found to be roughly independent of the incident energy, and substantially higher for structures with Mo on top. Several different types of defects are shown, and two general processes generating those are discussed. Trapping of the incoming noble gas was observed for the case of Kr impinging on structures with Mo as the top monolayer; this is interpreted as an effect of the small mass difference between the Mo and the Kr atoms. An increase in atomic mass of the gas translates into a more disparate behaviour of the studied structures. The energy exchange with the surface layer dictates the behaviour of the superlattice; this is accentuated when bombarding with the heavier gas, Kr.