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Percorrer por autor "Vandamme, L. K. J."

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  • Low-frequency diffusion noise in resistive-switching memories based on metal-oxide polymer structure
    Publication . Rocha, P. R. F.; Gomes, Henrique L.; Vandamme, L. K. J.; Chen, Q.; Kiazadeh, Asal; De Leeuw, Dago M.; Meskers, S. C. J.
    Low-frequency noise is studied in resistive-switching memories based on metal–oxide polymer diodes. The noise spectral power follows a 1/fγ behavior, with γ = 1 in the ohmic region and with γ = 3/2 at high bias beyond the ohmic region. The exponent γ = 3/2 is explained as noise caused by Brownian motion or diffusion of defects which induce fluctuations in diode current. The figure of merit to classify 1/f noise in thin films has an estimated value of 10−21 cm2/Ω, which is typical for metals or doped semiconductors. This value in combination with the low diode current indicates that the 1/f noise is generated in the narrow localized regions in the polymer between the contacts. The analysis unambiguously shows that the current in bistable nonvolatile memories is filamentary.
    2012Artigo científico Acesso restrito Ver mais
  • Low-frequency noise as a diagnostic tool for OLED reliability
    Publication . Rocha, Paulo R. F.; Vandamme, L. K. J.; Meskers, S. C. J.; Gomes, Henrique L.; De Leeuw, D. M.; Van De Weijer, P.
    Organic light emitting diodes (OLED), either based on polymers or small molecules, suffer from early failure: an unpredictable sudden increase in current with a total loss of light output. This work addresses this problem using small-signal impedance measurements and electrical noise techniques. Robust OLEDs show a current noise spectrum proportional to 1/f. OLEDs susceptible to failure have 1/f3/2 and/or may start exhibiting a standard 1/f behavior that rapidly evolves with time (typical 30 minutes) to 1/f1.6. In addition OLEDs susceptible to early failure have a higher DC leakage. It is proposed that a combination of both measurements can be used as a diagnostic tool for OLED reliability in a production line. Insight into the physics of the degradation mechanism is also provided. Unreliable OLEDs exhibit current switching events and optical blinks at wavelengths higher than the polymer band gap electroluminescence. It is proposed that degradation is induced by the appearance of an insulating resistive switching layer. Charge recombination trough this layer is responsible for the optical and electrical blinks. © 2013 IEEE.
    2013Documento de conferência Acesso restrito Ver mais