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Low-Temperature Raman Spectroscopy of Individual Single-Wall Carbon Nanotubes and Single-Layer Graphene

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journal contribution
posted on 11.09.2008, 00:00 by Li Zhang, Zhang Jia, Limin Huang, Stephen O’Brien, Zhonghua Yu
Confocal Raman microscopy was used to image and record the Raman spectra of individual single-wall carbon nanotubes (SWNTs) and single-layer graphene on silicon substrates at both room and low temperatures. The temperature-induced Raman spectral change of individual nanotubes is observed to be tube diameter dependent, with larger-diameter tubes typically exhibiting a higher upshift in Raman frequency on decreasing temperature. The temperature-induced shift in the G-band frequency of single layer graphene is found to be greater than that of nanotubes. These observations can be ascribed to the temperature dependence of carbon−carbon bond force constants in SWNTs, and the nanotube curvature effect respectively. The tube-substrate interaction is proposed to be the main factor in contributing to the diameter dependence of the temperature-induced radial breathing mode (RBM) frequency change in SWNTs. Evidence of chirality dependence of the temperature dependent Raman scattering in SWNTs is also revealed in this work. Individual metallic nanotubes exhibit a large variation in the temperature dependence of the Fano Raman peak, which can be explained in the context of Kohn anomaly mechanism due to different degrees of charge doping.