Highly oriented pyrolytic graphite (HOPG) is a highly pure and ordered form of synthetic

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

. 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. Note that the term "highly ''ordered'' pyrolytic graphite" is sometimes used for this material, but IUPAC favors "highly ''oriented''".

Synthesis

The method used to produce HOPG is based on the process used to make

pyrolytic graphite Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets as a result of imperfections in its production. Pyrolytic carbon is man-made and is thought not to be found in nature.Ratner, Buddy D. ...

, but with additional tensile stress in the basal-plane direction. This produces improved alignment of the graphite crystallites and an interplanar spacing close to that observed in natural graphite. The "stress recrystallization" of graphite was first described by L. C. F. Blackman and

Alfred Ubbelohde Alfred René Jean Paul Ubbelohde FRS (14 December 1907 – 7 January 1988) was a Belgian-born English physical chemist. Education, early life and career Ubbelohde was born in Antwerp, Belgium, in 1907. He was educated at St Paul's School, 192 ...

in 1962. The diameters of the individual crystallites in HOPG are typically in the range 1–10 μm.

Application

HOPG is used in x-ray optics as a monochromator and in

scanning probe microscopy Scan may refer to: Acronyms * Schedules for Clinical Assessment in Neuropsychiatry (SCAN), a psychiatric diagnostic tool developed by WHO * Shared Check Authorization Network (SCAN), a database of bad check writers and collection agency for bad ...

as a substrate and for magnification calibration.

References

{{Reflist Allotropes of carbon