Spatially resolved raman spectroelectrochemistry of solid-state polythiophene/viologen memory devices

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DOIResolve DOI: http://doi.org/10.1021/ja304458s
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TypeArticle
Journal titleJournal of the American Chemical Society
ISSN0002-7863
1520-5126
Volume134
Issue36
Pages1486914876; # of pages: 8
AbstractA three terminal molecular memory device was monitored with in situ Raman spectroscopy during bias-induced switching between two metastable states having different conductivity. The device structure is similar to that of a polythiophene field effect transistor, but ethylviologen perchlorate was added to provide a redox counter-reaction to accompany polythiophene redox reactions. The conductivity of the polythiophene layer was reversibly switched between high and low conductance states with a “write/erase” (W/E) bias, while a separate readout circuit monitored the polymer conductance. Raman spectroscopy revealed reversible polythiophene oxidation to its polaron form accompanied by a one-electron viologen reduction. “Write”, “read”, and “erase” operations were repeatable, with only minor degradation of response after 200 W/E cycles. The devices exhibited switching immediately after fabrication and did not require an “electroforming” step required in many types of memory devices. Spatially resolved Raman spectroscopy revealed polaron formation throughout the polymer layer, even away from the electrodes in the channel and drain regions, indicating that thiophene oxidation “propagates” by growth of the conducting polaron form away from the source electrode. The results definitively demonstrate concurrent redox reactions of both polythiophene and viologen in solid-state devices and correlate such reactions with device conductivity. The mechanism deduced from spectroscopic and electronic monitoring should guide significant improvements in memory performance.
Publication date
LanguageEnglish
AffiliationSecurity and Disruptive Technologies; National Research Council Canada
Peer reviewedYes
NPARC number21269028
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Record identifiere1b1f52b-470d-4fbb-911c-0f2a45f23548
Record created2013-12-02
Record modified2016-05-09
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