Probing Graphene Edges via Raman Scattering

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• 作者：Awnish K. Gupta ; Timothy J. Russin ; Humberto R. Gutiérrez ; Peter C. Eklund
• 刊名：ACS Nano
• 出版年：2009
• 出版时间：January 27, 2009
• 年：2009
• 卷：3
• 期：1
• 页码：45-52
• 全文大小：502K
• 年卷期：0
• ISSN：1936-086X

文摘

We present results of a Raman scattering study from the region near the edges of n-graphene layer films. We find that a Raman band (D) located near 1344 cmp>−1p> (514.5 nm excitation) originates from a region next to the edge with an apparent width of ∼70 nm (upper bound). The D-band was found to exhibit five important characteristics: (1) a single Lorentzian component for n = 1, and four components for n = 2−4, (2) an intensity I_D ∼ cosp>4p> θ, where θ is the angle between the incident polarization and the average edge direction, (3) a local scattering efficiency (per unit area) comparable to the G-band, (4) dispersive behavior (∼50 cmp>−1p>/eV for n = 1), consistent with the double resonance (DR) scattering mechanism, and (5) a scattering efficiency that is almost independent of the crystallographic orientation of the edge. High-resolution transmission electron microscope images reveal that our cleaved edges exhibit a sawtooth-like roughness of ∼3 nm (i.e., ∼20 times the C−C bond length). We propose that in the double resonance Raman scattering process the photoelectron scatters diffusely from our edges, obscuring the recently proposed strong variation in the scattering from armchair versus zigzag symmetry edges based on theoretical arguments.