title: From tunneling to hopping: a comprehensive investigation of charge transport mechanism in molecular junctions based on oligo(p-phenylene ethynylene)s.
abstract: The charge transport mechanism of oligo(p-phenylene ethynylene)s with lengths ranging from 0.98 to 5.11 nm was investigated using modified scanning tunneling microscopy break junction and conducting probe atomic force microscopy methods. The methods were based on observing the length dependence of molecular resistance at single molecule level and the current-voltage characteristics in a wide length distribution. An intrinsic transition from tunneling to hopping charge transport mechanism was observed near 2.75 nm. A new transitional zone was observed in the long length molecular wires compared to short ones. This was not a simple transition between direct tunneling and field emission, which may provide new insights into transport mechanism investigations. Theoretical calculations provided an essential explanation for these phenomena in terms of molecular electronic structures.
authors.affiliation: Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Lu
authors.forename: Ke
authors.initials: K
authors.lastname: Liu
authors.forename: Hongming
authors.initials: H
authors.lastname: Zhang
authors.forename: Zhibo
authors.initials: Z
authors.lastname: Du
authors.forename: Xianhong
authors.initials: X
authors.lastname: Wang
authors.forename: Fosong
authors.initials: F
authors.lastname: Wang
mesh_terms: D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D004579:Electron Transport; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008956:Models, Chemical; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D011108:Polymers; C473966:poly(phenylene ethynylene)