X-Ray Diffuse Scattering by Highly Oriented Pyrolytic Graphite

The X-ray diffuse scattering intensity was measured for a highly oriented pyrolytic graphite (HOPG) sample as well as for a single crystal kish graphite sample. The measurements were carried out both at 10 K and at room temperature. The HOPG sample gives rise to a temperature independent diffuse scattering along the c * -direction. This scattering was analyzed as that due to the crystallite boundaries. The thermal diffuse scattering exhibits unusual features which could be interpreted to be a result of the coupling of low frequency phonons with an excitation mode which is yet to be identified.