Evidence for strain-induced local conductance modulations in single-layer graphene on SiO2.
Graphene has emerged as an electronic material that is promising for device applications and for studying two-dimensional electron gases with relativistic dispersion near two Dirac points. Nonetheless, deviations from Dirac-like spectroscopy have been widely reported with varying interpretations. Here we show evidence for strain-induced spatial modulations in the local conductance of single-layer graphene on SiO(2) substrates from scanning tunneling microscopic (STM) studies. We find that strained graphene exhibits parabolic, U-shaped conductance vs bias voltage spectra rather than the V-shaped spectra expected for Dirac fermions, whereas V-shaped spectra are recovered in regions of relaxed graphene. Strain maps derived from the STM studies further reveal direct correlation with the local tunneling conductance. These results are attributed to a strain-induced frequency increase in the out-of-plane phonon mode that mediates the low-energy inelastic charge tunneling into graphene.
Teague
M L
ML
Department of Physics, California Institute of Technology, Pasadena, California 91125, USA.
Lai
A P
AP
Velasco
J
J
Hughes
C R
CR
Beyer
A D
AD
Bockrath
M W
MW
Lau
C N
CN
Yeh
N-C
NC
D004553:Electric Conductivity; D004581:Electronics; D004583:Electrons; D005740:Gases; D006108:Graphite / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
D005740:Gases; D012822:Silicon Dioxide; D006108:Graphite