Self-assembled monolayers (SAMs) are widely used in a variety of emerging applications for surface modification of metals and oxides. Here, we demonstrate a new type of molecular self-assembly: the growth of organosilane SAMs at the surface of organic semiconductors. Remarkably, SAM growth results in a pronounced increase of the surface conductivity of organic materials, which can be very large for SAMs with a strong electron-withdrawing ability. For example, the conductivity induced by perfluorinated alkyl silanes in organic molecular crystals approaches 10−5 S per square, two orders of magnitude greater than the maximum conductivity typically achieved in organic field-effect transistors. The observed large electronic effect opens new opportunities for nanoscale surface functionalization of organic semiconductors with molecular self-assembly. In particular, SAM-induced conductivity shows sensitivity to different molecular species present in the environment, which makes this system very attractive for chemical sensing applications.
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We thank A. Zakhidov, J. E. Anthony, E. Garfunkel and Y. Chabal for helpful discussions and S.-W. Cheong and S. Park for technical assistance with AFM. This work has been supported by the NSF grants DMR-0405208 and ECS-0437932.
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Calhoun, M., Sanchez, J., Olaya, D. et al. Electronic functionalization of the surface of organic semiconductors with self-assembled monolayers. Nature Mater 7, 84–89 (2008). https://doi.org/10.1038/nmat2059
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