Stable Molecular Diodes Based on π–π Interactions of the Molecular Frontier Orbitals with Graphene Electrodes |
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| Authors: | Peng Song Sarah Guerin Sherman Jun Rong Tan Harshini Venkata Annadata Xiaojiang Yu Micheál Scully Ying Mei Han Max Roemer Kian Ping Loh Damien Thompson Christian A. Nijhuis |
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| Affiliation: | 1. Department of Chemistry, National University of Singapore, Singapore, Singapore;2. Department of Physics, Bernal Institute, University of Limerick, Limerick, Ireland;3. Singapore Synchrotron Light Source, National University of Singapore, Singapore, Singapore;4. Centre for Advanced 2D Materials, Graphene Research Centre, National University of Singapore, Singapore, Singapore;5. NUSNNI‐Nanocore, National University of Singapore, Singapore, Singapore |
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| Abstract: | In molecular electronics, it is important to control the strength of the molecule–electrode interaction to balance the trade‐off between electronic coupling strength and broadening of the molecular frontier orbitals: too strong coupling results in severe broadening of the molecular orbitals while the molecular orbitals cannot follow the changes in the Fermi levels under applied bias when the coupling is too weak. Here, a platform based on graphene bottom electrodes to which molecules can bind via π–π interactions is reported. These interactions are strong enough to induce electronic function (rectification) while minimizing broadening of the molecular frontier orbitals. Molecular tunnel junctions are fabricated based on self‐assembled monolayers (SAMs) of Fc(CH2)11X (Fc = ferrocenyl, X = NH2, Br, or H) on graphene bottom electrodes contacted to eutectic alloy of gallium and indium top electrodes. The Fc units interact more strongly with graphene than the X units resulting in SAMs with the Fc at the bottom of the SAM. The molecular diodes perform well with rectification ratios of 30–40, and they are stable against bias stressing under ambient conditions. Thus, tunnel junctions based on graphene with π–π molecule–electrode coupling are promising platforms to fabricate stable and well‐performing molecular diodes. |
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| Keywords: | charge transport graphene electrodes molecular diodes molecular electronics π – π interactions |
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