Abstract
Current-voltage (IV) characteristics and the temperature dependence of the contact resistance [R(T)] of Au/YBa2Cu3O7−δ (optimally doped YBCO) interfaces have been studied at different resistance states. These states were produced by resistive switching after accumulating cyclic electrical pulses of increasing number and voltage amplitude. The IV characteristics and the R(T) dependence of the different states are consistent with a Poole-Frenkel (P-F) emission mechanism with trapping-energy levels Et in the 0.06–0.11 eV range. Et remains constant up to a number-of-pulses-dependent critical voltage and increases linearly with a further increase in the voltage amplitude of the pulses. The observation of a P-F mechanism reveals the existence of an oxygen-depleted layer of YBCO near the interface. A simple electrical transport scenario is discussed, where the degree of disorder, the trap energy level, and the temperature range determine an electrical conduction dominated by non-linear effects, either in a P-F emission or in a variable-range hopping regime.
Highlights
Metal-YBa2Cu3O7–d (YBCO) interfaces on ceramic and thin-films samples have both shown bipolar RS characteristics.8–11 Their retentivity12,13 as well as their response to cyclic electric field stresses14 have been previously studied
Most probably related to a random distribution of oxygen vacancies near the junction, we present a description of the electrical conduction based on a modified Variable-Range Hopping (VRH) mechanism
As our results indicate that the main conduction mechanism through the Au/YBCO interface is a P-F emission, we have to consider that transport properties are dominated by a carrier-trap region in the YBCO part of the junction
Summary
Metal-YBa2Cu3O7–d (YBCO) interfaces on ceramic and thin-films samples have both shown bipolar RS characteristics. Their retentivity as well as their response to cyclic electric field stresses have been previously studied. Our results indicate that a P-F emission mechanism dominates the current-voltage dependence of the junction, indicating the existence of carrier traps and of a low conductivity region in the interfacial YBCO. Within this scenario, most probably related to a random distribution of oxygen vacancies near the junction, we present a description of the electrical conduction based on a modified Variable-Range Hopping (VRH) mechanism. The modification that we propose is based on considering that the available electrical carriers are only those thermally or voltage assisted de-trapped which obey a P-F law In this framework, we show that increasing the amplitude or the number of applied pulses has qualitatively the same microscopic effect on modifying the trap energy level as well as the resistivity and the geometric factor of a conducting channel
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