Ultraviolet and visible Raman spectroscopies of the graphitic BCx phases

Ultraviolet (UV) Raman and visible Raman spectroscopies were applied to study the graphitic BCx (g-BCx) phases. The Raman spectra of the g-BCx phases excited with UV laser at 244 nm have one main peak: a G peak (approximately at 1590 cm(-1)), and do not have the D peak (around 1350 cm(-1)) characteristic for Raman spectra of disordered graphitic phases. The D peak can be detected in all g-BCx phases when green (534 nm) or near-infrared (785 nm) lasers are used for Raman scattering excitation. The positions of the G and D peaks were found to be independent (within the experimental errors) of the B/C ratio. The pattern of the peaks in UV Raman spectra of g-BC2.1 phase indicates that the additional peaks centered at 1089 cm(-1) should be assigned to the E-g mode of B4C vibration rather than to the T mode characteristic to amorphous graphite, The high signal-to-noise (S/N) ratio and lack of fluorescence of the UV Raman spectra allow an accurate measure of bandwidth and frequency of the G peaks. (C) 2009 Elsevier B.V. All rights reserved.