Highly ordered pyrolytic graphite (HOPG)

HOPG is widely used as a substrate for specimens to be examined in scanning probe microscopy. It is also used as a calibration specimen and cleaves almost like mica because of its layered structure. Unlike mica, HOPG is non-polar and,for samples where elemental analysis is required, it provides a carbon-only background. It consists of highly ordered planes of carbon atoms in (002) orientation and the quality of these parallel planes is defined by the mosaic spread angle.

The standard grade of HOPG has a mosaic angle of 3.5° ±1.5°, while substrates with more highly ordered planes, with mosaic angles of 0.8° ±0.2° and 0.4° ±0.1°, are also available.