title: Exceptional Single-Molecule Transport Properties of Ladder-Type Heteroacene Molecular Wires.
abstract: A series of ladder-type fused heteroacenes consisting of thiophenes and benzothiophenes were synthesized and functionalized with thiol groups for single-molecule electrical measurements via a scanning tunneling microscopy break-junction method. It was found that this molecular wire system possesses exceptional charge transport properties with weak length dependence. The tunneling decay constant β was estimated to be 0.088 and 0.047 Å(-1) under 0.1 and 0.5 bias, respectively, which is one of the lowest β values among other non-metal-containing molecular wires, indicating that a planar ladder structure favors charge transport. Transition voltage spectroscopy showed that the energy barrier decreases as the length of the molecule increases. The general trend of the energy offsets derived from the transition voltage via the Newns-Anderson model agrees well with that of the Fermi/HOMO energy level difference. Nonequilibrium Green's function/density functional theory was used to further investigate the transport process in these molecular wires.
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Zhengxu
authors.initials: Z
authors.lastname: Cai
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Wai-Yip
authors.initials: WY
authors.lastname: Lo
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Tianyue
authors.initials: T
authors.lastname: Zheng
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Lianwei
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Yubing
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Chemistry and the James Franck Institute, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
authors.forename: Luping
authors.initials: L
authors.lastname: Yu