HOPG

Highly oriented pyrolytic graphite (HOPG) is a highly pure and ordered form of synthetic graphite. It is characterised by a low mosaic spread angle, meaning that the individual graphite crystallites are well aligned with each other. The best HOPG samples have mosaic spreads of less than 1 degree. It is used in x-ray optics as a monochromator and in scanning probe microscopy as a substrate and for magnification calibration.