Raman spectra of graphite edge planes; edge planes of HOPG prepared by Ar ion cutting and Kish graphite formed on its crystal grain

摘要

Only a few studies on Raman scattering from graphite edge planes have been conducted using HOPG edge planes, because of difficulty in preparation. Compagnini et al. found a feature at 1351 cm~(-1) for the virgin edge plane of their HOPG sample in addition to the G band at 1580 cm~(-1) using the 514.5 nm excitation. After irradiating with Ar ions, they obtained a doublet D band for the edge plane and an additional feature at 1360 cm~(-1) for the basal plane of HOPG (Compagnini et al. 1997). For the doublet D band, they determined the position of the lower energy peak (Dpline) at 1351 cm~(-1) and the higherenergy peak (D_2-line) at 1360 cm~(-1). They attributed also the D_1-line to the rupture of the space symmetry D_(6h)~4 and the D_2-line to the disorder induced line. Kawashima and Katagiri measured a singlet D band at 1355 cm~(-1) for the polished edge plane of HOPG (Kawashima and Katagiri 1999). They also measured a weak feature at 1621 cm~(-1) (D' band) and related it to disorder. However, Compagnini et al. did not mention the D' band. On the other hand, Tan et al. studied Raman scattering from natural graphite edge planes (Tan et al. 2004). They reported two features of Raman spectra showing clear doublets of D and D' bands for three different laser excitations. For the 514.5 nm excitation, the D band was found to consist of the D_1-line at 1352 cm~(-1) and the D_2-line at 1369 cm~(-1) while the D' band was comprised of the D'_1-line at 1620 cm~(-1) and the D'_2-line at 1624 cm~(-1).A method to prepare the edge plane of graphite crystal such as HOPG using Ar-ion polishing was developed in the present study. Measurement of the first order Raman spectrum was conducted in the present study on the edge plane of HOPG thus prepared to examine details of the D band and also the appearance of the D' band in relation to the D band. The measurements were also made for edge planes of Kish graphite crystals, for comparison.