Electronic Reflections

Aranya Goswami, graduate student
Electrical and Computer Engineering


Electron waves reflecting off a crystal, form interference patterns that can light up phosphor screens. These can be used to probe and study the material. This image shows such a pattern arising from a crystalline sample of indium phosphide, a material important for both electronics and photonics.

The technique of obtaining this pattern is known as reflection high energy electron diffraction (RHEED).  On analyzing these patterns, we can understand things like crystallinity of the sample, the exact arrangement of atoms  on the surface of this crystal and the spatial symmetries that the crystal exhibits. What is amazing is that, through tiny changes in the shape and brightness of these streaks in the interference image, RHEED can detect changes of a single layer of extra atoms on the sample surface in real time. This in turn allows us to control crystal growths with unprecedented precision - one atomic layer at a time.  These RHEED images were taken using 12kV  electrons in a chemical beam epitaxy chamber and were tiled using standard image processing software.