Photo-emission electron microscopy was used to study Cu diffusion through a Ru thin film. The photo-emission electron microscopic images revealed a high contrast between Cu and Ru, due to the difference in work function. This made photo-emission electron microscopy an ideal methodology for studying thin-film diffusion in real time. At between 175 and 290C, the Cu diffused mainly through defect sites in the thin Ru film. Uniform diffusion of Cu through the Ru film began at about 300C. The results were confirmed by X-ray photo-emission spectroscopy depth-profiling and scanning electron microscopy–energy dispersive X-ray spectroscopy.

Study of Copper Diffusion through a Ruthenium Thin Film by Photoemission Electron Microscopy. W.Wei, S.L.Parker, Y.M.Sun, J.M.White, G.Xiong, A.G.Joly, K.M.Beck, W.P.Hess: Applied Physics Letters, 2007, 90[11], 111906