Ambipolar Transport in an Electrochemically Gated Single-Molecule Field-Effect Transistor

• Published in: ACS nano 2012-08, Vol.6 (8), p.7044-7052
• Main Authors: Díez-Pérez, Ismael, Li, Zhihai, Guo, Shaoyin, Madden, Christopher, Huang, Helin, Che, Yanke, Yang, Xiaomei, Zang, Ling, Tao, Nongjian
• Format: Article
• Language: English
• Subjects: Blocking; Charge transport; Electric potential; Electrochemistry - instrumentation; Electron Transport; Energy gap; Equipment Design; Equipment Failure Analysis; Field effect transistors; Gates; Materials Testing; Molecular orbitals; Nanostructures - chemistry; Nanostructures - ultrastructure; Particle Size; Signal Processing, Computer-Assisted - instrumentation; Transistors, Electronic; Transport; Voltage
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn302090t

Charge transport is studied in single-molecule junctions formed with a 1,7-pyrrolidine-substituted 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) molecular block using an electrochemical gate. Compared to an unsubstituted-PTCDI block, spectroscopic and electrochemical measurements indicate a reduction in the highest occupied (HOMO)–lowest unoccupied (LUMO) molecular orbital energy gap associated with the electron donor character of the substituents. The small HOMO–LUMO energy gap allows for switching between electron- and hole-dominated charge transports as a function of gate voltage, thus demonstrating a single-molecule ambipolar field-effect transistor. Both the unsubstituted and substituted molecules display similar n-type behaviors, indicating that they share the same n-type conduction mechanism. However, the substituted-PTCDI block shows a peak in the source–drain current vs gate voltage characteristics for the p-type transport, which is attributed to a two-step incoherent transport via the HOMO of the molecule.