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Research Project
Organic Nanomaterials for Electronics and Photonics: Design, Synthesis, Characterization, Processing, Fabrication and Applications
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Publications
Lithium fluoride injection layers can form quasi-Ohmic contacts for both holes and electrons
Publication . Bory, B. F.; Rocha, Paulo R. F.; Janssen, R. A. J.; Gomes, Henrique L.; de Leeuw, D. M.; Meskers, S. C. J.
Thin LiF interlayers are typically used in organic light-emitting diodes to enhance the electron injection. Here, we show that the effective work function of a contact with a LiF interlayer can be either raised or lowered depending on the history of the applied bias. Formation of quasi-Ohmic contacts for both electrons and holes is demonstrated by electroluminescence from symmetric LiF/polymer/LiF diodes in both bias polarities. The origin of the dynamic switching is charging of electrically induced Frenkel defects. The current density-electroluminescence-voltage characteristics can qualitatively be explained. The interpretation is corroborated by unipolar memristive switching and by bias dependent reflection measurements. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Lithium fluoride injection layers can form quasi-Ohmic contacts for both holes and electrons
Publication . Bory, Benjamin F.; Rocha, Paulo; Janssen, Rene A. J.; Gomes, Henrique L.; De Leeuw, Dago M.; Meskers, Stefan C. J.
Thin LiF interlayers are typically used in organic light-emitting diodes to enhance the electron injection. Here, we show that the effective work function of a contact with a LiF interlayer can be either raised or lowered depending on the history of the applied bias. Formation of quasi-Ohmic contacts for both electrons and holes is demonstrated by electroluminescence from symmetric LiF/polymer/LiF diodes in both bias polarities. The origin of the dynamic switching is charging of electrically induced Frenkel defects. The current density-electroluminescence-voltage characteristics can qualitatively be explained. The interpretation is corroborated by unipolar memristive switching and by bias dependent reflection measurements. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon
Publication . Bory, Benjamin F.; Rocha, Paulo; Gomes, Henrique L.; de Leeuw, Dago M.; Meskers, Stefan C. J.
Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 10(17) m(-2). We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching. (C) 2015 Author(s).
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Funding agency
European Commission
Funding programme
FP7
Funding Award Number
212311