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Supramolecular tunnelling junctions with robust high rectification based on assembly effects
Date
2024
Abstract
The performance of large-area molecular diodes can in rare cases approach the lower limit of commercial semiconductor devices but predictive structure–property design remains difficult as the rectification ratio (R) achieved by self-assembled monolayer (SAM) based diodes depends on several intertwined parameters. This paper describes a systematic approach to achieve high rectification in bisferrocenyl-based molecular diodes, HSCnFc–CuC–Fc (n = 9–15) immobilised on metal surfaces (Ag, Au and Pt). Experiments supported by molecular dynamics simulations show that the molecular length and bottom electrode influence the SAM packing, which affects the breakdown voltage (VBD), the associated maximum R (Rmax), and the bias at which the Rmax is achieved (Vsat,R). From the electrical characterisation of the most stable Pt–SCnFc– CuC–Fc//GaOx/EGaIn junctions, we found that VBD, Vsat,R, and Rmax all scale linearly with the spacer length of Cn, and that Rmax for all the SAMs consistently exceeds the “Landauer limit” of 103 . Our data shows that the robust switching of M–SCnFc–CuC–Fc//GaOx/EGaIn junctions is the result of the combined optimisation of parameters involving the molecular structure, the type of metal substrate, and the applied operating conditions (bias window), to create stable and high-performance junctions.
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Description
Publisher
Royal Society of Chemistry
Citation
Nanoscale, 2024,
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Funding Information
We acknowledge the Minister of Education (MOE) for supporting this research under award no. MOE2015-T2-1-050. Prime Minister’s Office, Singapore under its Medium sized centre program is also acknowledged for supporting this research. The authors would also like to acknowledge the Singapore Synchrotron Light Source (SSLS) for providing the facility necessary for spectroscopic measurements. We thank Dr Li Jiang for providing the Au, Ag and Pt substrates. X. C. thanks the support under the Natural Science Foundation of Fujian Province, China (Grant No. 2022J05173). D. T. thanks Science Foundation Ireland (SFI) for financial support under Grant Number 12/RC/2275_P2 (SSPC), and for provision of computing resources at the SFI/Higher Education Authority Irish Centre for High-End Computing (ICHEC)