Title
Observation of low energy Raman modes in twisted bilayer graphene
Date Issued
14 August 2013
Access level
open access
Resource Type
journal article
Author(s)
He R.
Chung T.F.
Delaney C.
Keiser C.
Shand P.M.
Chancey C.C.
Wang Y.
Bao J.
Chen Y.P.
Purdue University
Publisher(s)
American Chemical Society
Abstract
Two new Raman modes below 100 cm-1 are observed in twisted bilayer graphene grown by chemical vapor deposition. The two modes are observed in a small range of twisting angle at which the intensity of the G Raman peak is strongly enhanced, indicating that these low energy modes and the G Raman mode share the same resonance enhancement mechanism, as a function of twisting angle. The ∼94 cm-1 mode (measured with a 532 nm laser excitation) is assigned to the fundamental layer breathing vibration (ZO′ mode) mediated by the twisted bilayer graphene lattice, which lacks long-range translational symmetry. The dependence of this mode's frequency and line width on the rotational angle can be explained by the double resonance Raman process that is different from the previously identified Raman processes activated by twisted bilayer graphene superlattice. The dependence also reveals the strong impact of electronic-band overlaps of the two graphene layers. Another new mode at ∼52 cm-1, not observed previously in the bilayer graphene system, is tentatively attributed to a torsion mode in which the bottom and top graphene layers rotate out-of-phase in the plane. © 2013 American Chemical Society.
Start page
3594
End page
3601
Volume
13
Issue
8
Language
English
OCDE Knowledge area
Nano-tecnología
Subjects
Scopus EID
2-s2.0-84881576704
Source
Nano Letters
ISSN of the container
1530-6984
Sponsor(s)
National Science Foundation 0847638
Sources of information:
Directorio de Producción Científica
Scopus