Physical origin of spontaneous interfacial alloying in immiscible W/Cu multilayers

A metastable solid solution has been observed in immiscible W/Cu multilayers sputter deposited with very low period ( £ 3 nm). A recent model evidencing size dependence of surface energies and diffusion coefficients in bilayers may explain the observed trends since diffusion coefficients highly increase when layer thickness decreases. Furthermore, implantation effects of the energetic incoming atoms during layer deposition undoubtedly reinforce these mixing phenomena.