The influence of surface diffusion on surface roughness and component distribution profiles during deposition of multilayers

The kinetic processes taking place on the surface and influencing the depth distribution of components during deposition of multilayers are considered by proposed kinetic model. The depth distribution of components in growing structure, broadening of interfaces between layers and shape of concentration peaks of multilayers are analyzed with respect of evolution of surface roughness during deposition. Surface roughness depends on adsorption rate and on surface diffusion. In presented model, the process of surface diffusion is subdivided into up-diffusion and down-diffusion. It is shown that atomic fluxes of up-diffusion and down-diffusion do not compensate each other even in the case of equal diffusion coefficients as they depend on coverage of different monolayers. Down-diffusion results in smoother surface, in contrary, up-diffusion makes it rougher. It is quantitatively shown by kinetic modeling that with increase of down-diffusion the amplitude of concentration peaks of components increases, the broadening of interface between layers decreases and concentration peaks become asymmetrical. The asymmetry of concentration peaks is found even in the case of equal diffusion coefficients of different components. At different diffusivity of components, the asymmetry is following: the concentration peaks of heavy-component (less diffusivity) show enhanced trailing tails on the back profile side (for light-component on the contrary). Up-diffusion results in increase of surface roughness and broadening of interface between layers. The quantitative functions of surface roughness on ratio of up- and down- diffusion coefficients are calculated and analyzed.