Electron Holographic Observations at Boundaries Aligned Parallel and Nonparallel to the Incident Beam

The changes in phase profiles across heterointerfaces and the ability to detect intergranular amorphous phases were investigated using off-axis electron holography in a field-emission transmission electron microscope. The boundaries were viewed in the conventional edge-on orientation, and also after tilting so that the boundary was no longer parallel to the incident beam. Reconstructed phase images of W/Si multilayers demonstrate that the boundaries are still apparent even at substantial tilts (up to 6°), and that the shape of the phase profile changes as expected with tilt. Detection of thin (<1nm) glassy phases at grain boundaries in Ti-doped Al2O3 with minor silicon impurities was then explored. The amorphous aluminosilicate phase displays a significantly larger phase shift than the adjoining alumina grains, and can be apparent at tilts up to nearly 10°. An undecorated boundary shows very little change in phase at the interface.