Applications of electron holography to the study of interfaces

Electron holography has been applied to a variety of layered structures to assess its usefulness for supplying information about composition profiles across heterogeneous interfaces. The phase of the exit-surface electron wave, which to a first approximation is dependent upon the mean inner potential and the specimen thickness, was extracted from electron holograms acquired from suitable cross-sectional multilayer specimens. Line profiles from the reconstructed phase images were analyzed to obtain information about interface diffuseness and layer width with a spatial resolution of about 5 Å. Using spatial averaging parallel to the interface, increased measurement precision was obtainable in some special cases. Differences in interdiffusion widths between Mo-Si and Si-Mo interfaces in an Mo/Si multilayer structure were confirmed, and the width of the amorphous layer at Si₃N₄ grain boundaries was measured to be about 12 Å. It was concluded that off-axis electron holography represented a useful complementary technique for characterizing interfaces.