Raman spectroscopy on heavy ion-induced surface modifications of graphite

Fine-grained isotropic graphite is the material of choice for the production target and the beam catchers at the planned Super-FRS fragment separator at FAIR. Heavyion irradiation studies of graphite are needed, as radiation damage will ultimately limit the lifetime of these components. Polycrystalline graphite and highly-oriented pyrolytic graphite (HOPG) were irradiated with energetic ions and subsequently analyzed by Raman spectroscopy as a non-intrusive technique for measuring the degree of structural order and residual stress in the surface layer. The first-order Raman spectrum is commonly used for the characterization of disordered carbon. It exhibits a graphite (G) peak at 1580 cm −1 and a disorder-related (D) peak at 1360 cm −1 . The G peak is well defined for HOPG and starts to broaden in materials containing a disordered phase, e.g. irradiated HOPG and polycrystalline graphite (Fig.1). The band position has also been shown to change with stress and temperature [1].