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Browsing by Author "Bory, B. F."

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  • 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.
    2014Journal article Open access Show more
  • Relation between the electroforming voltage in alkali halide-polymer diodes and the bandgap of the alkali halide
    Publication . Bory, B. F.; Wang, J. X.; Gomes, Henrique L.; Janssen, R. A. J.; de Leeuw, D. M.; Meskers, S. C. J.
    Electroforming of indium-tin-oxide/alkali halide/poly(spirofluorene)/Ba/Al diodes has been investigated by bias dependent reflectivity measurements. The threshold voltages for electrocoloration and electroforming are independent of layer thickness and correlate with the bandgap of the alkali halide. We argue that the origin is voltage induced defect formation. Frenkel defect pairs are formed by electron-hole recombination in the alkali halide. This self-accelerating process mitigates injection barriers. The dynamic junction formation is compared to that of a light emitting electrochemical cell. A critical defect density for electroforming is 10(25)/m(3). The electroformed alkali halide layer can be considered as a highly doped semiconductor with metallic transport characteristics. (C) 2014 Author(s).
    2014Journal article Open access Show more
  • Role of Hole Injection in Electroforming of LiF-Polymer Memory Diodes
    Publication . Bory, B. F.; Gomes, Henrique L.; Janssen, R. A. J.; de Leeuw, D. M.; Meskers, S. C. J.
    Al/LiF/poly(spirofluorene)/Ba/Al diodes submitted to bias voltages near 15 V undergo a change to a nonvolatile memory known as electroforming. Prior to electroforming, electron trapping occurs, followed by a tunneling current due to electrons from the polymer into LiF. At the onset voltage for electroforming, a sudden electroluminescence burst originating from electronic excitations in the polymer is detected. This confirms that hole injection into the polymer through LiF occurs leading to nonvolatile resistive switching.
    2012Journal article Restricted access Show more