Introduction

HOPG – Highly Ordered Pyrolytic Graphite is a very pure and highly ordered form of synthetic graphite. It is characterised by by the mosaic spread angle. HOPG is a laminar material and consists of layered polycrystals resembling a mosaic of monocrystals grains which are slightly disorientated with respect to each other. The size of the individual crystals varies from 1-10um. A lower mosaic spread angle represents a better alignment of the graphite crystals. The best HOPG samples have a mosaic spread value of less than 1 degree. The freshly cleaved HOPG substrates provides atomically flat areas which are used as a specimen substrate and for magnification calibration in scanning probe microscopy techniques (AFM, SPM, STM). Similar to mica, fresh surfaces can be made by cleaving the samples.
HOPG is made by annealing graphite under pressure at temperatures over 3000°C. This conductive material is stable up to 2000°C.°
Available in three qualities with 0.4, 0.8 and 3.5 degrees mosaic spread. Sample size is 10x10mm and thickness is 1 or 2 mm. The samples are all double sided which means that the full thickness can be used and they can be cleaved from both sides.