Gate-Controlled Energy Barrier at a Graphene/Molecular Semiconductor Junction

• Published in: Advanced functional materials Vol. 25; no. 20; pp. 2972 - 2979
• Main Authors: Parui, Subir, Pietrobon, Luca, Ciudad, David, Vélez, Saül, Sun, Xiangnan, Casanova, Fèlix, Stoliar, Pablo, Hueso, Luis E.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.05.2015
• Subjects: energy barrier; fullerene: graphene; photocurrent; vertical field effect transistor
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201403407

The formation of an energy‐barrier at a metal/molecular semiconductor junction is a universal phenomenon which limits the performance of many molecular semiconductor‐based electronic devices, from field‐effect transistors to light‐emitting diodes. In general, a specific metal/molecular semiconductor combination of materials leads to a fixed energy‐barrier. However, in this work, a graphene/C60 vertical field‐effect transistor is presented in which control of the interfacial energy‐barrier is demonstrated, such that the junction switches from a highly rectifying diode at negative gate voltages to a highly conductive nonrectifying behavior at positive gate voltages and at room temperature. From the experimental data, an energy‐barrier modulation of up to 660 meV, a transconductance of up to five orders of magnitude, and a gate‐modulated photocurrent are extracted. The ability to tune the graphene/molecular semiconductor energy‐barrier provides a promising route toward novel, high performance molecular devices. Graphene is an ideal candidate for the source electrode in a vertical organic field effect transistor as it has low density of states near the Dirac point and easy gate tunability of the Fermi‐level. By varying the gate electric field, the energy‐barrier is modulated at a graphene/molecular‐semiconductor (fullerene) junction, thus opening a promising route toward molecular‐semiconductor based devices.