Poole-Frenkel effect and Variable-Range Hopping conduction in metal / YBCO resistive switching devices

摘要

Current-voltage (IV) characteristics and the temperature dependence of thecontact resistance [$R(T)$] of Au / YBa$_2$Cu$_3$O$_{7-\delta}$ (optimallydoped YBCO) interfaces have been studied at different resistance states. Thisstates were produced by resistive switching after accumulating cyclicelectrical pulses of increasing number and voltage amplitude. The IVcharacteristics and the $R(T)$ dependence of the different states areconsistent with a Poole-Frenkel (P-F) emission mechanism with trapping-energylevels $E_t$ in the 0.06-0.11 eV range. $E_t$ remains constant up to anumber-of-pulses-dependent critical voltage and increases linearly with furtherincreasing the voltage amplitude of the pulses. The observation of a P-Fmechanism reveals the existence of an oxygen-depleted layer of YBCO near theinterface. A simple electrical transport scenario is discussed, where thedegree of disorder, the trap energy level and the temperature range determinean electrical conduction dominated by non-linear effects, or by a P-F emissionor by a Variable-Range Hopping regime.