Charge carrier transition in an ambipolar single-molecule junction: Its mechanical-modulation and reversibility

Jian Shao,Yun Chen,Yue Zheng,Xiaoyue Zhang

doi:10.1038/s41524-016-0003-x

Jian Shao, Yun Chen + Show 2 more

Open Access

https://doi.org/10.1038/s41524-016-0003-x

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Abstract

AbstractPrecise control from the bottom-up for realizing tunable functionality is of utmost importance to facilitate the development of molecular electronic devices. Until now, however, manipulating charge carriers over single-molecule scale remains intractable. The origin of the problem is that the nature of charge carriers is often hindered by the complexity of the investigated molecular systems. Here, via ab initio simulations, we show a force-modulated and switched ambipolar single-molecule junction with Au/cyclopropane-1,2-dithiol/Au structure. The cyclopropane ring in the molecule can be opened and closed reversibly and repeatedly by the mechanical force. This structural transition from its closed state to open state enables the ambipolarity in charge carriers—from p-type to n-type. Analysis of electronic structure reveals unambiguously the force-dependent correlation between C–S bond order and the nature of charge carriers. Based on this, we design a binary interconnected junction exhibiting resistance, rectification and negative differential resistance functionalities under mechanical modulation, i.e., loading/unloading or pull/push. This interesting phenomenon provides both illuminating insight and feasible controllability into charge carriers in molecules, and a very general idea and useful approach for single-molecule junctions in practical single-molecule devices.

Highlights

Molecular electronics exploits bottom-up approaches to build functional and tunable devices with minimized dimensions.[1]
The bonds in the above individual cases are formed by different atoms, and the influence of bond order has not been confirmed
First we validate the transformation of Au/CPDT/Au junction under external forces through Car-Parrinello molecular dynamics (CPMD) simulation

Summary

INTRODUCTION

Molecular electronics exploits bottom-up approaches to build functional and tunable devices with minimized dimensions.[1] The key to this next-generation technology is the design of architecture and the control of transport in each molecular block.[2]. We utilized mechanical forces to manipulate the bond order and the charge carrier of Au/cylcopropane-1,2-dithiol (CPDT)/Au junction. This molecule keeps cyclopropane backbone and has a general representativeness for a wide range of its derivatives. The distance of C–S bond decreases from 1.77 to 1.64 Å, indicating an increase in bond order. (Literatures[24] give a single C–S bond length of ~1.8 Å and double one of ~1.6 Å.) As there is increase in the C–S bond order, the electrons from the breaking of

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