Electron holography study on the microstructure of magnetic tunnelling junctions

Electron holography was applied to study the microstructure evolution of magnetic tunnelling junctions (MTJs) CoFe/AlOx/Co annealed at different temperatures. A mean inner potential barrier was observed in the as-deposited MTJ sample, while it was changed to a potential well after a 200°C or a 400°C annealing. It is suggested that the oxygen atoms were redistributed during the annealing, which left metallic atoms acting as acceptors to confine the electrons, leading to the decrease of the potential of the AlOx barrier layer. The results suggest that the electron holography may be a useful tool for the study of the microstructure of amorphous materials.