Studies of Intrinsic Hot Phonon Dynamics in Suspended Graphene by Transient Absorption Microscopy

Correlated transient absorption and atomic force microscopy (AFM) measurements have been performed for monolayer graphene, both free-standing and supported on a glass substrate. The AFM images allow us to locate regions of the suspended graphene. The transient absorption traces show a fast instrumen...

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Bibliographic Details
Published in:Nano letters 2011-08, Vol.11 (8), p.3184-3189
Main Authors: Gao, Bo, Hartland, Gregory, Fang, Tian, Kelly, Michelle, Jena, Debdeep, Xing, Huili (Grace), Huang, Libai
Format: Article
Language:English
Subjects:
Atomic force microscopy
Channels
Charge carriers
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Decomposition
Diffusion in nanoscale solids
Diffusion in solids
Diffusion rate
Exact sciences and technology
Excitation
Fullerenes and related materials
diamonds, graphite
Graphene
Materials science
Nanostructure
Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation
Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
Phonons
Physics
Specific materials
Transport properties of condensed matter (nonelectronic)
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Summary:Correlated transient absorption and atomic force microscopy (AFM) measurements have been performed for monolayer graphene, both free-standing and supported on a glass substrate. The AFM images allow us to locate regions of the suspended graphene. The transient absorption traces show a fast instrument response limited decay, followed by a slower intensity dependent decay. The fast decay is assigned to a combination of coupling between the excited charge carriers and the optical phonon modes of graphene and the substrate, and diffusion of the charge carrier out of the probe region. The slow decay is due to the hot phonon effect and reflects the lifetime of the intrinsic optical phonons of graphene. The time constant for the slow decay is longer for suspended graphene compared to substrate-supported graphene. This is attributed to interactions between the excited charge carriers and the surface optical phonon modes of the substrate, which supplies an additional relaxation channel for supported graphene.
ISSN:1530-6984
1530-6992
DOI:10.1021/nl201397a