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Effects of Heat Treatment on Raman Spectra of Two‐Layer 12 C/ 13 C Graphene
Author(s) -
Kalbac Martin,
Frank Otakar,
Kavan Ladislav
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201202114
Subject(s) - graphene , raman spectroscopy , materials science , layer (electronics) , graphene nanoribbons , spectral line , atmospheric temperature range , silicon , substrate (aquarium) , nanotechnology , analytical chemistry (journal) , chemistry , optoelectronics , optics , physics , thermodynamics , organic chemistry , oceanography , astronomy , geology
The Raman spectra of two‐layered graphene on a silicon substrate were studied in the temperature range from 298 to 1073 K in an inert atmosphere. Isotopic engineering was used to fabricate two‐layer graphene specimens containing 13 C atoms in the top layer and 12 C atoms in the bottom layer, which allowed the behavior of each particular layer to be distinguished as a function of temperature. It is demonstrated that the top layer exhibits much lower Raman temperature coefficients than the bottom one for both the G and the G′ modes. We suggest that the changes in the Raman spectra of graphene observed during thermal cycling are predominantly caused by a superposition of two effects, namely, the mechanical stress in graphene exerted by the substrate and the intrinsic changes in the graphene lattice caused by the temperature itself. The top graphene layer is proposed to be more relaxed than the bottom graphene layer and thus reflects almost exclusively the temperature variations as a freestanding graphene layer would.

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