Negative differential resistance and resistive switching behaviors in Cu2S nanowire devices
ABSTRACT Two-terminal devices of Cu2S/ZnO core/shell nanowires were fabricated and measured. Forward bias sweeping produced a rectified I-V characteristic of a diode, with turn-on voltages varying from 150 to 300 mV. The turn-on voltages depended on the rate at which the bias was varied. When the bias scan was reversed, a resistive switching (RS) behavior was observed. A low-resistance state was measured, and the diode characteristic diminished. At -50 to -150 mV, negative differential resistance (NDR) was observed, after which the diode behavior was restored. This phenomenon was explained using the diffusion of Cu+ within Cu2S. ZnO acted to limit RS to the positive bias range and NDR to the negative bias range.
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ABSTRACT: Memristive devices are promising components for nanoelectronics with applications in nonvolatile memory and storage, defect-tolerant circuitry, and neuromorphic computing. Bipolar resistive switches based on metal oxides such as Ti O <sub>2</sub> have been identified as memristive devices primarily based on the “pinched hysteresis loop” that is observed in their current-voltage (i-v) characteristics. Here we show that the mathematical definition of a memristive device provides the framework for understanding the physical processes involved in bipolar switching and also yields formulas that can be used to compute and predict important electrical and dynamical properties of the device. We applied an electrical characterization and state-evolution procedure in order to capture the switching dynamics of a device and correlate the response with models for the drift diffusion of ionized dopants (vacancies) in the oxide film. The analysis revealed a notable property of nonlinear memristors: the energy required to switch a metal-oxide device decreases exponentially with increasing applied current.Journal of Applied Physics 11/2009; · 2.21 Impact Factor
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ABSTRACT: Both ac impedance and dc polarization have been measured to investigate the switching property of a Cu2S gapless type atomic switch with two-probe cells composed of asymmetric configuration of ion blocking and reversible electrodes in addition to symmetric one with reversible electrodes. Strong nonlinear p-type conductivity in current--voltage (I--V) characteristics and a marked change of overall ac impedance with the variation of applied dc bias voltage observed are attributed to the nonstoichiometry induced carrier modification in a Cu2S thin film modulated by the Cu vacancy migration under the presence of an electrical potential field.Applied Physics Express - APPL PHYS EXPRESS. 01/2009; 2.
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ABSTRACT: Thin-film polycrystalline CdS/Cu 2 S cells with energy conversion efficiencies in sunlight of up to 9.15 percent and areas of ∼1 cm<sup>2</sup>have been developed. The improvement over previously achieved efficiencies is due to the development of techniques to separately measure and minimize fill factor losses. Specific design and fabrication changes based on a detailed quantitative analysis of the cell operation, were introduced to correct series resistance, shunt conductance and field effect losses. Further increases in efficiency can be expected from the development of a planar junction thin-film CdS/Cu 2 S cell.IEEE Transactions on Electron Devices 05/1980; · 2.06 Impact Factor