title: Evidence for strain-induced local conductance modulations in single-layer graphene on SiO2.
abstract: 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.
authors.affiliation: Department of Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Teague
authors.forename: A P
authors.initials: AP
authors.lastname: Lai
authors.forename: J
authors.initials: J
authors.lastname: Velasco
authors.forename: C R
authors.initials: CR
authors.lastname: Hughes
authors.forename: A D
authors.initials: AD
authors.lastname: Beyer
authors.forename: M W
authors.initials: MW
authors.lastname: Bockrath
authors.forename: C N
authors.initials: CN
authors.lastname: Lau
authors.forename: N-C
authors.initials: NC
authors.lastname: Yeh
mesh_terms: 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
chemical_list: D005740:Gases; D012822:Silicon Dioxide; D006108:Graphite