Applications of electron holography to multilayer interfaces

Electron holography has received renewed interest recently as a means of resolution enhancement in high resolution phase contrast imaging and as a technique for imaging microscopic magnetic domain structures. Some of the original applications of the technique involved measurement of the absolute mean inner potential in films of known thickness. This approach has now been extended in order to gain information about changes in elemental concentrations at interfaces in multilayer films.The abruptness of interfaces in multilayer films used for X-ray mirrors strongly affects their reflective properties. Previous studies using high resolution phase contrast imaging have shown that this interface diffuseness can be imaged, but typically with low contrast and an unknown contribution from amplitude contrast effects. The differences in mean inner potential between successive layers suggests that the variation of the mean inner potential across the interface should be a good measurement of the change in elemental concentration.