Tuning Charge Transport in Aromatic‐Ring Single‐Molecule Junctions via Ionic‐Liquid Gating

Abstract

Achieving gate control with atomic precision, which is crucial to the transistor performance on the smallest scale, remains a challenge. Herein we report a new class of aromatic‐ring molecular nanotransistors based on graphene–molecule–graphene single‐molecule junctions by using an ionic‐liquid gate. Experimental phenomena and theoretical calculations confirm that this ionic‐liquid gate can effectively modulate the alignment between molecular frontier orbitals and the Fermi energy level of graphene electrodes, thus tuning the charge‐transport properties of the junctions. In addition, with a small gate voltage (|VG|≤1.5 V) ambipolar charge transport in electrochemically inactive molecular systems (EG>3.5 eV) is realized. These results offer a useful way to build high‐performance single‐molecule transistors, thus promoting the prospects for molecularly engineered electronic devices.

Improving Gating Efficiency of Electron Transport through Redox‐Active Molecular Junctions with Conjugated Chains

“…Up to date, this electrochemical gating has been successfully applied in tuning electron transport through various types of molecular junctions under various environments. [7] Among them, redox-active molecules could be converted between the oxidized and reduced states upon different electrochemical potentials, and have been widely studied to illustrate the electrochemical gating at single-molecule level, such as ferrocene, [8] pyrrolo-tetrathiafulvalene, [9] anthraquinone, [10] viologen, [11] transition metal complex [8a,12] and redox-active DNA or proteins. [13] Their conductance could switch on as the energy level of electrodes shifted to resonance with molecules.…”

Side-group chemical gating via reversible optical and electric control in a single molecule transistor

“…One mode is asymmetric stochastic conductance switching due to electric field-induced isomerisation of azobenzene and the other is reversible photoswitching at low biases. Note that this azobenzene single-molecule transistor, which is switched between an ON and OFF state because the two isomers have the different resistances, is different from common single-molecule transistors in which the source-drain currents can be continuously tuned by using the gate voltage 9,39 . A crucial discovery is that both quantum mechanical calculations and experimental data reveal that an electric field can unambiguously modulate the energy difference between trans and cis forms, as well as the energy barrier of conformational changes.…”

Redox Control of Charge Transport in Vertical Ferrocene Molecular Tunnel Junctions

“…Charge transport through single or self-assembled monolayer (SAM) of molecules has attracted great interest in the past two decades [1][2][3][4][5][6][7][8] due to the potential applications of molecular tunnel junctions beyond current scaling limits as diodes, [9][10][11][12] switches, [13][14][15][16] and transistors. 17,18 Furthermore, charge tunneling transport underpins basic physical and chemical mechanisms at the molecular level, such as room-temperature quantum interference (QI) effects, [19][20][21][22] thermoelectricity, 23,24 and dynamic chemical processes. [25][26][27][28] Traditionally, SAM-based molecular tunnel junctions were constructed with functional SAMs sealed within parallel-plane electrodes, [29][30][31][32][33] such as ferrocene (Fc) SAMs between an ultra-flat bottom electrode and an EGaIn top electrode.…”