Direct spectroscopic monitoring of conductance switching in polythiophene memory devices

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Journal titleElectrochimica Acta
Pages437445; # of pages: 9
SubjectSolid state redox; Poly-thiophene; Atmospheric effects; Conductance switching; Mechanism of memory; Non-volatile memory; Nonvolatile memory devices; Raman spectroscopic; Spectroscopic monitoring; Electrolytic reduction; Molecular electronics; Nonvolatile storage; Organic polymers; Polarons; Polymer films; Redox reactions; Refractory metal compounds; Semiconductor doping
AbstractA large number of nonvolatile memory devices have been reported with both inorganic and organic components, and many of these involve changes in device resistance between a high conductivity "ON" state and a low conductivity "OFF" state. The mechanism of memory action in many of these devices is uncertain, and may be based on many phenomena, including redox reactions, metal filament formation, charge storage in "floating gates", and redistribution of oxide vacancies. We report here a Raman spectroscopic probe of organic polymer memory devices which permits direct monitoring of the doping state and conductivity of polythiophene in a 3-terminal device. The polymer conductance is controlled by voltage pulses between the source and gate electrodes in FET geometry, while the conductance state is read out by a separate circuit between source and drain. The conductance was directly correlated with the Raman determination of the density of polarons in the polymer film, which was shown to control both the "electroforming" process and the conductance switching in working memory devices. The polymer conductance change requires a redox counter-reaction at the gate electrode, and atmospheric effects on performance indicate that water and oxygen reduction are involved. The observations are consistent with a redox process between the gate and source electrodes which modulates the polaron concentration and source-drain conductivity. This mechanism provides a framework for optimization of the device by changing its composition and geometry, particularly the identity of the redox counter-reaction and control of ion mobility. © 2012 Elsevier Ltd. All rights reserved.
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AffiliationNational Research Council Canada (NRC-CNRC); Security and Disruptive Technologies
Peer reviewedYes
NPARC number21271795
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Record identifierc96c89b5-65c8-498a-9f00-3aa035c84727
Record created2014-04-22
Record modified2016-05-09
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