Unipolar Resistive Switching and Associated Photoresponse in Sm doped BiFeO 3 Thin Film Grown by RF Sputtering
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Unipolar Resistive Switching and Associated Photoresponse in Sm doped BiFeO3 Thin Film Grown by RF Sputtering Rajesh K. Katiyar1, Pankaj Misra1,G. L Sharma1,Gerardo Morell 1, J. F Scott1,2 , Ram S. Katiyar1 1 Department of Physics and Institute for Functional Nano materials, University of Puerto Rico, San Juan, Puerto Rico, PR-00936, USA 2 Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 OHE, UK ABSTRACT Nonvolatile unipolar resistive switching has been observed in Sm doped BFO thin films in Pt/Sm: BFO/SRO stack geometry. The initial forming voltage was found to be ~ 11 V. After the forming process repeatable switching of the resistance of Sm:BFO film was obtained between low and high resistance states with nearly constant resistance ratio ~ 105 and non overlapping switching voltages in the range of 0.7-1 V and 4-6 V respectively. The temperature dependent measurements of the resistance of the device indicated metallic and semiconducting conduction behavior in low and high resistance states respectively. The current conduction mechanism of the Pt/Sm:BFO/SRO device in low resistance states was found to be dominated by the Ohmic behavior while in case of high resistance state and at high voltages it deviated significantly from normal Ohmic behavior and was found to correspond the Pool-Frankel (PF) emission. The Pt/Sm:BFO/SRO structure also showed efficient photo-response in high and low resistance states with increase in photocurrent which was significantly higher in low resistance state when illuminated with white light. INTRODUCTION Studies on resistive switching behavior in well known multiferroic material BiFeO3(BFO) and its variants have received tremendous attention recently due to their potential in developing futuristic multifunctional devices combining ferroelectricity, ferromagnetism, photovoltaic and charge conduction as it offers additional degrees of freedom for BFO-based multifunctional devices [1]. There have been many reports on the multiferroic property of BFO, however reports on resistive switching behavior and associated photo-voltaic response along with underlying mechanisms in polycrystalline BFO is scanty. In a recent report the bipolar resistive switching has been reported for epitaxial BFO thin films grown on single-crystal substrates however the ratio of two resistance states (high and low) was limited to ~100 due to large leakage current [2]. This ratio can be improved significantly by reducing the leakage current of BFO through suitable doping [3]. In this paper we report unipolar resistive switching in Sm doped BiFeO3 (Sm:BFO) thin films with ratio of high and low resistance states as high as ~105. Photo-response in these films in low and high resistance states is also reported. EXPERIMENT The Sm (5%) doped BFO thin films were deposited using in-house developed RF magnetron sputtering setup. Sm:BFO target was prepared in-house by the conventional solid
state reaction root using predetermined amount of high-purity Bi2O3 (99.99%), Fe2O3, and Sm2O3 (99.98%)
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