Grazing incidence diffraction
Grazing incidence diffraction (GID) is a technique for interrogating a material using small incidence angles for an incoming wave, often leading to the diffraction being surface sensitive. It occurs in many different areas: Reflection high-energy electron diffraction (RHEED), where electrons of relatively high energy diffract at small angles from a surface.
Source: Wikipedia — Grazing incidence diffraction (CC BY-SA 4.0)