title: Single-molecule diodes with high rectification ratios through environmental control.
abstract: Molecular electronics aims to miniaturize electronic devices by using subnanometre-scale active components. A single-molecule diode, a circuit element that directs current flow, was first proposed more than 40 years ago and consisted of an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Several single-molecule diodes have since been realized in junctions featuring asymmetric molecular backbones, molecule-electrode linkers or electrode materials. Despite these advances, molecular diodes have had limited potential for applications due to their low conductance, low rectification ratios, extreme sensitivity to the junction structure and high operating voltages. Here, we demonstrate a powerful approach to induce current rectification in symmetric single-molecule junctions using two electrodes of the same metal, but breaking symmetry by exposing considerably different electrode areas to an ionic solution. This allows us to control the junction's electrostatic environment in an asymmetric fashion by simply changing the bias polarity. With this method, we reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide. By taking advantage of the changes in the junction environment induced by the presence of an ionic solution, this method provides a general route for tuning nonlinear nanoscale device phenomena, which could potentially be applied in systems beyond single-molecule junctions.
authors.affiliation: Department of Applied Physics and Applied Mathematics, New York, New York 10027, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Capozzi
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Jianlong
authors.initials: J
authors.lastname: Xia
authors.affiliation: Department of Applied Physics and Applied Mathematics, New York, New York 10027, USA.
authors.forename: Olgun
authors.initials: O
authors.lastname: Adak
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Dell
authors.affiliation: Molecular Foundry, Lawrence Berkeley National Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Zhen-Fei
authors.initials: ZF
authors.lastname: Liu
authors.affiliation: Department of Applied Physics and Applied Mathematics, New York, New York 10027, USA.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Taylor
authors.affiliation: 1] Molecular Foundry, Lawrence Berkeley National Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA [2] Kavli Energy NanoSciences Institute at Berkeley, Berkeley, California 94720, USA.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Neaton
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Luis M
authors.initials: LM
authors.lastname: Campos
authors.affiliation: 1] Department of Applied Physics and Applied Mathematics, New York, New York 10027, USA [2] Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Latha
authors.initials: L
authors.lastname: Venkataraman
mesh_terms: D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012666:Semiconductors