Anomalous K-Point Phonons in Noble Metal/Graphene Heterostructure Activated by Localized Surface Plasmon Resonance

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Title
Anomalous K-Point Phonons in Noble Metal/Graphene Heterostructure Activated by Localized Surface Plasmon Resonance
Author
Kim, Un JeongKim, Jun SukPark, NoejungLee, SanghyubPark, YeonsangSeok, JinbongHwang, SungwooSon, HyungbinLee, Young Hee
Issue Date
2018-12
Publisher
AMER CHEMICAL SOC
Citation
ACS NANO, v.12, no.12, pp.12733 - 12741
Abstract
The metal/graphene interface has been one of the most important research topics with regard to charge screening, charge transfer, contact resistance, and solar cells. Chemical bond formation of metal and graphene can be deduced from the defect induced D-band and its second-order mode, 2D band, measured by Raman spectroscopy, as a simple and nondestructive method. However, a phonon mode located at ∼1350 cm-1, which is normally known as the defect-induced D-band, is intriguing for graphene deposited with noble metals (Ag, Au, and Cu). We observe anomalous K-point phonons in nonreactive noble metal/graphene heterostructures. The intensity ratio of the midfrequency mode at ∼1350 cm-1 over G-band (∼1590 cm-1) exhibits nonlinear but resonant behavior with the excitation laser wavelength, and more importantly, the phonon frequency-laser energy dispersion is ∼10-17 cm-1 eV-1, which is much less than the conventional range. These phonon modes of graphene at nonzero phonon wave vector (q ≠ 0) around K points are activated by localized surface plasmon resonance and not by the defects due to chemical bond formation of metal/graphene. This hypothesis is supported by density functional theory (DFT) calculations for noble metals and Cr along with the measured contact resistances.
URI
https://scholarworks.unist.ac.kr/handle/201301/25611
URL
https://pubs.acs.org/doi/10.1021/acsnano.8b07761
DOI
10.1021/acsnano.8b07761
ISSN
1936-0851
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