Abstract
Resistive switching heterojunctions, which are promising for nonvolatile memory applications, usually share a capacitorlike metal-oxide-metal configuration. Here, we report on the nonvolatile resistive switching in heterostructures, where the conducting layer near the interface serves as the “unconventional” bottom electrode although both oxides are band insulators. Interestingly, the switching between low-resistance and high-resistance states is accompanied by reversible transitions between tunneling and Ohmic characteristics in the current transport perpendicular to the planes of the heterojunctions. We propose that the observed resistive switching is likely caused by the electric-field-induced drift of charged oxygen vacancies across the interface and the creation of defect-induced gap states within the ultrathin layer. These metal-oxide-oxide heterojunctions with atomically smooth interfaces and defect-controlled transport provide a platform for the development of nonvolatile oxide nanoelectronics that integrate logic and memory devices.
3 More- Received 31 August 2012
DOI:https://doi.org/10.1103/PhysRevX.3.041027
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Published by the American Physical Society
Popular Summary
A wide range of electronic, optical, and energy-harvesting devices base their operations on reliable and reversible switching of electric resistance between high and low values in their material components. Commonly used capacitors that perform such switching are based on thin films of metal-oxide-metal “sandwiches.” In this paper, we report systematic nanosecond-rate resistive switching experiments in fundamentally different and particularly interesting thin-film devices composed of a metal layer (platinum) and two ultrathin insulating oxide layers ( and ), where such switching of electronic transport was not expected, according to the conventional wisdom of electronic transport.
One of the unusual reasons for the resistive switching we have observed lies in the region near the interface. Although both and are prototypical insulators, their interfacial region can exhibit a range of much more interesting electronic behavior, from a metallic to a superconducting electron gas. In our devices, this interfacial region in its metallic state serves as an electrode.
The other relevant players in the out-of-plane resistive switching are charge-carrying oxygen vacancies, defects ubiquitous in oxides. Our new insight, supported by both experiments and first-principles theoretical calculations, is that the locations of the oxygen vacancies in the oxides can be reconfigured by short electrical pulses on the scale of nanoseconds such that an insulator-to-metal transition can be induced and controlled in a reversible way. Such reversible transitions due to ionic dynamics ultimately lead to the fast resistive switching.
Our result should be a fundamental contribution to oxide electronics based on ultrathin heterostructures and may open new avenues for device engineering and applications.