Conformation vs voltage gating in a molecular transistor: A first-principles quantum chemical study

Abstract

The electronic conduction of a novel, three-terminal molecular architecture is studied under the influence of conformational or voltage gating and also when both are simultaneously present. At the ground state configuration, the calculated tunneling current (I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> ) as a function of external bias (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</inf> ) exhibits typical insulator-semiconductor behaviour. However, a significant increase, by more than an order of magnitude, and a distinct variation in the current are predicted in its operational mode (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</inf> >1.5V) when additional non-planarity is induced in the triphenyl chain. The observed conformational gating affects the current via localization/delocalization of the electronic wave function in the conduction channel. As the gate-field is turned on, the transport is affected via “enhancement” or “depletion” mode of a transistor, attributed to the intrinsic dipolar molecular architecture. The current modulation is found to reach its maximum only under exclusive effect of voltage or conformational gating and diminishes when both of them are present.