Spatially Resolved Raman Spectroelectrochemistry of Solid-State Polythiophene/Viologen Memory Devices
| Autor: | Rajesh Kumar, Richard L. McCreery, Rajesh G. Pillai, Yiliang Wu, Nikola Pekas |
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| Rok vydání: | 2012 |
| Předmět: |
Time Factors
Polymers Analytical chemistry Thiophenes Spectrum Analysis Raman Polaron Biochemistry Viologens Catalysis chemistry.chemical_compound symbols.namesake Colloid and Surface Chemistry medicine Molecular memory Molecular Structure business.industry Conductance Viologen General Chemistry chemistry Electrode symbols Polythiophene Optoelectronics Field-effect transistor business Raman spectroscopy Oxidation-Reduction medicine.drug |
| Zdroj: | Journal of the American Chemical Society. 134:14869-14876 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja304458s |
| Popis: | A 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. |
| Databáze: | OpenAIRE |
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