Raman spectroscopic investigation of ion-beam-irradiated glassy carbon

Abstract

Raman spectroscopy has been used to monitor the changes induced in glassycarbon as a result of irradiation with H, He, C, N, Si, and Xe ions. The Raman spectrum of unirradiated glassycarbon consists of an intrinsic graphite peak at 1590 cm−1 (the a peak) and a disorder‐induced D peak at 1350 cm−1. The G peak position and FWHM and the ratio of the D peak intensity to that of the G peak [I(D)/I(G)] are plotted as functions of the calculated damage density induced by the ion beam. The results show that at very low damage levels [ < 0.008 displacements per atom (DPA)], considerable disorder is being introduced into the system, and the average crystallite size has been reduced from 35 Å for the unirradiated material to about 25 Å. At damage levels of ∼0.21 DPA, the material starts to undergo an ion‐beam‐induced modification which saturates at about 5 DPA. The Raman spectra for these heavily irradiated samples are very similar to those obtained from amorphous carbons. At yet higher doses there is some evidence suggesting that ion‐beam‐induced partial graphitization of the irradiated glassycarbon has occurred. The results are discussed in the context of previously reported Raman studies of amorphous carbons and highly oriented pyrolytic graphite.