Crystal quality

The quality of a crystal cannot be measured directly. However, measurements on several physical properties can be compared to standards for pure and homogenous crystals. The half-width of an XRD reflection is such a property.

The quality of the crystalline lattice is determined by its regularity. Defects, dislocations and contaminations are imperfections which exist in every lattice. Other discontinuities are grain boundaries and cracks. All these features cause local strain in the surrounding lattice. This can be measured by recording the rocking curve of an X-ray reflection. The geometrical properties of the incident beam and the resulting rocking curve half-width allow to characterizes the surface quality.