Quantum Interference Enhances the Performance of Single-Molecule Transistors

TL;DR

This paper demonstrates that quantum interference effects in single-molecule transistors can significantly enhance their performance, achieving high conductance-switching ratios and stability by exploiting destructive interference in electron transmission.

Contribution

The study provides the first experimental evidence that quantum interference can be harnessed to improve molecular transistor performance, with detailed theoretical and experimental analysis.

Findings

Achieved >10^4 conductance-switching ratio

Demonstrated subthreshold swing at thermionic limit

Operated at >7 kHz frequency with high stability

Abstract

An unresolved challenge facing electronics at a few-nm scale is that resistive channels start leaking due to quantum tunneling. This affects the performance of nanoscale transistors, with single-molecule devices displaying particularly low switching ratios and operating frequencies, combined with large subthreshold swings.1 The usual strategy to mitigate quantum effects has been to increase device complexity, but theory shows that if quantum effects are exploited correctly, they can simultaneously lower energy consumption and boost device performance.2-6 Here, we demonstrate experimentally how the performance of molecular transistors can be improved when the resistive channel contains two destructively-interfering waves. We use a zinc-porphyrin coupled to graphene electrodes in a three-terminal transistor device to demonstrate a >104 conductance-switching ratio, a subthreshold swing at the thermionic limit, a > 7 kHz operating frequency, and stability over >105 cycles. This performance is competitive with the best nanoelectronic transistors. We fully map the antiresonance interference features in conductance, reproduce the behaviour by density functional theory calculations, and trace back this high performance to the coupling between molecular orbitals and graphene edge states. These results demonstrate how the quantum nature of electron transmission at the nanoscale can enhance, rather than degrade, device performance, and highlight directions for future development of miniaturised electronics.