Reflection High Energy Electron Diffraction (RHEED), Low Energy Electron Diffraction (LEED) & X-ray Diffraction (XRD) The crystallographic structure of materials can be monitored using electron or x-ray diffraction techniques. The differentially pumped reflection high energy electron diffraction (RHEED) system included in the Thin Film Synthesis and Characterization Facility can monitor thin film structure during growth. This capability