期刊
NANO LETTERS
卷 14, 期 8, 页码 4615-4621出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl501678j
关键词
layer breathing mode; shear mode; few layer; graphene; Raman; adsorption
类别
资金
- American Chemical Society Petroleum Research Fund [53401-UNI10]
- National Science Foundation [DMR-1337207]
- UNI Faculty Summer Fellowship
- Yangtze University [2013cjp15]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1337207] Funding Source: National Science Foundation
We investigated the low-frequency Raman spectra of freestanding few-layer graphene (FLG) at varying temperatures (400-900 K) controlled by laser heating. At high temperature, we observed the fundamental Raman mode for the lowest-frequency branch of rigid-plane layer-breathing mode (LBM) vibration. The mode frequency redshifts dramatically from 81 cm(-1) for bilayer to 23 cm(-1) for 8-layer. The thickness dependence is well described by a simple model of coupled oscillators. Notably, the LBM Raman response is unobservable at room temperature, and it is turned on at higher temperature (>600 K) with a steep increase of Raman intensity. The observation suggests that the LBM vibration is strongly suppressed by molecules adsorbed on the graphene surface but is activated as desorption occurs at high temperature.
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