Energetic inert gas atom impact effects during ion beam multilayer deposition

New magnetic field sensors and non-volatile magnetic random access memories can be built from giant magnetoresistive multilayers with nanoscale thickness. The performance of these devices is enhanced by decreasing the atomic scale interfacial roughness and interlayer mixing of the multilayers. During ion beam sputtering, inert gas neutrals with energies between 50 and 200 eV impact the growth surface. A molecular dynamics method has been used to study the effects of these impacts on the surface roughness and interlayer mixing of model nickel/copper multilayers. The results indicate that impacts with energy above 50 eV cause mixing due to the exchange of Ni atoms with Cu atoms in an underlying Cu crystal. The extent of the mixing increases with impact energy, but decreases as the number of the Ni monolayers above the Cu crystal increases. While Xe and Ar impacts have a similar mixing effect at low energies, heavier Xe ions/neutrals induce more significant mixing at high energies.