Controlling piezoresistance in single molecules through the isomerisation of bullvalenes

Jeffrey R Reimers; Tiexin Li; André P Birvé; Likun Yang; Albert C Aragonès; Thomas Fallon; Daniel S Kosov; Nadim Darwish

doi:10.1038/s41467-023-41674-z

Controlling piezoresistance in single molecules through the isomerisation of bullvalenes

Nat Commun. 2023 Oct 3;14(1):6089. doi: 10.1038/s41467-023-41674-z.

Authors

Jeffrey R Reimers^{1

2}, Tiexin Li³, André P Birvé⁴, Likun Yang⁵, Albert C Aragonès^{6

7}, Thomas Fallon⁸, Daniel S Kosov⁹, Nadim Darwish¹⁰

Affiliations

¹ International Centre for Quantum and Molecular Structures and the Department of Physics, Shanghai University, Shanghai, 200444, China. jeffrey.reimers@uts.edu.au.
² School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, NSW, 2007, Australia. jeffrey.reimers@uts.edu.au.
³ School of Molecular and Life Sciences, Curtin University, Bentley, WA, 6102, Australia.
⁴ School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW, 2308, Australia.
⁵ International Centre for Quantum and Molecular Structures and the Department of Physics, Shanghai University, Shanghai, 200444, China.
⁶ Department of Materials Science and Physical Chemistry, University of Barcelona, Marti i Franquès 1, 08028, Barcelona, Catalonia, Spain.
⁷ Institute of Theoretical and Computational Chemistry, University of Barcelona, Diagonal 645, 08028, Barcelona, Catalonia, Spain.
⁸ School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW, 2308, Australia. thomas.fallon@newcastle.edu.au.
⁹ College of Science and Engineering, James Cook University, Townsville, QLD, 4811, Australia. daniel.kosov@jcu.edu.au.
¹⁰ School of Molecular and Life Sciences, Curtin University, Bentley, WA, 6102, Australia. nadim.darwish@curtin.edu.au.

Abstract

Nanoscale electro-mechanical systems (NEMS) displaying piezoresistance offer unique measurement opportunities at the sub-cellular level, in detectors and sensors, and in emerging generations of integrated electronic devices. Here, we show a single-molecule NEMS piezoresistor that operates utilising constitutional and conformational isomerisation of individual diaryl-bullvalene molecules and can be switched at 850 Hz. Observations are made using scanning tunnelling microscopy break junction (STMBJ) techniques to characterise piezoresistance, combined with blinking (current-time) experiments that follow single-molecule reactions in real time. A kinetic Monte Carlo methodology (KMC) is developed to simulate isomerisation on the experimental timescale, parameterised using density-functional theory (DFT) combined with non-equilibrium Green's function (NEGF) calculations. Results indicate that piezoresistance is controlled by both constitutional and conformational isomerisation, occurring at rates that are either fast (equilibrium) or slow (non-equilibrium) compared to the experimental timescale. Two different types of STMBJ traces are observed, one typical of traditional experiments that are interpreted in terms of intramolecular isomerisation occurring on stable tipped-shaped metal-contact junctions, and another attributed to arise from junction‒interface restructuring induced by bullvalene isomerisation.