No abstract

Erasable conductive domain walls (DWs) in insulating ferroelectrics are key components to reconfigurable nanocircuitries, nanosensors, and memories, but the wall currents are found to decay with time, especially at high temperatures. In this study, DW currents are induced upon partial domain switching against the peripheral unswitched bulk domain under the application of in‐plane electric field between two top electrodes patterned on epitaxial BiFeO3 (BFO) thin films. The “on” currents are followed by a drop at higher bias above the coercive voltage, which becomes more significant at elevated temperature from 298 to 408 K. An opposite “on” current is observed in the back sweeping when the above walls are erased to restore the as‐grown, stable domain structure. The phenomenon is explained by a film defect‐related model that free charges are injected and locally trapped at the defect levels to help screen the uncompensated polarizations in the conducting DWs, resulting in the wall current reduction. Once the walls are erased at opposite coercive voltages, the trapped free charges at the conducting DWs are expelled to form a discharge current. This finding provides the fundamental physics of the wall conduction in correlation with the film defects and reversible charge injection.

No abstract

Electric transport in the charged domain wall (CDW) region has emerged as a promising phenomenon for the development of next-generation ferro-resistive memory with ultrahigh data storage density. However, accurately measuring the conductivity of CDWs induced by polarization reversal remains challenging due to the polarization modulation of the Schottky barrier at the thin film−electrode interface, which could partially contribute to the collected "on" current of the device. Here, we propose carefully selecting an electrode that can suppress the effect of interfacial barrier modulation induced by polarization reversal, allowing the collected current mainly from the conductive CDWs. The experiment was conducted on epitaxial BiFeO 3 (001) thin-film devices with vertical and horizontal geometries. Piezo-response force microscopy scanning showed the local polarization experienced 180°rotation to form CDWs under the vertical electric field. However, devices with SrRuO 3 epitaxial top electrodes still exhibit an interfacial barrierdominated diode behavior, with the "on" current proportional to the electrode area. To identify the CDW current, more interfacial defects were introduced by the deposition of Pt top electrodes, which significantly enhanced charge injection for the compensation of the reversed polarization driven by the electric field, leading to the suppressed polarization modulation of the Schottky barrier height. It was observed that the current flow through Pt electrodes is significantly lower compared to that of SRO electrodes and appears to be primarily influenced by the electrode perimeter instead of the electrode area, indicating CDW-dominated conduction behavior in these devices. Planar nanodevices were further fabricated to support the quantitative investigation of the Pt electrode size-dependent "on" current with a linear fit of the current magnitude versus the CDW cross-sectional area. This work constitutes an essential part of understanding the role of the CDW current in ferro-resistive memory devices.