Investigation of Resistive Switching at SrRuO 3 /Cr-doped SrZrO 3 /Metal Junctions
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0997-I04-04
Investigation of Resistive Switching at SrRuO3/Cr-doped SrZrO3/Metal Junctions Hwan-Soo Lee Data Storage Systems Center, Carnegie Mellon University, Pittsburgh, PA, 15213 ABSTRACT We have investigated charge transport properties with current perpendicular to the plane across the interface between a Cr-doped SrZrO3 perovskite oxide film and different top electrode metals. The measured resistance showed a wide variation depending on the top electrode metal, and suggested the interfacial properties with respect to contacting electrode metal kinds are responsible for the change in I-V characteristics (IVCs). The observed I-V curves were modeled with the equation I(V) = aV+bV2, where the variation of a was related to the work function of the metal whereas the variation of b was related to the oxygen affinity of the metal, consistent with space charge limited conduction through a defected interface. Additionally, the resistive switching was attributed to a change in both the a and the b coefficients. We speculate that voltage (or current) induced vacancy motion accounts for a change in trap density in the oxide near the metallic electrical contact, and trapping or detrapping of charge carriers, showing the conductivity modulation across the junction. INTRODUCTION Perovskite oxides such as Cr-doped SrZrO3 (SZO) [1], Pr0.7Ca0.3MnO3 (PCMO) [2], and LaxCa1-xMnO3 (LCMO) [3], where the conductivity of localized regions was shown to be modulated through the application of voltage (or current) perpendicular to the film, are of great interest as storage material for next generation nonvolatile memory (NVM). Although a model based on the storage and release of charge carriers in the oxide could be conceivable for the observed switching and memory behavior in these compounds, a detailed and quantitative understanding of the physical mechanism remains a matter of debate. In this work, we have prepared epitaxial thin film stacks of perovskite materials on SrTiO3 substrates having the following structures: substrate/SrRuO3/Cr-doped SrZrO3/top electrode metal (these structures are similar to the reported by others [1]). We present investigations into the role of the top electrode (TE) on the resistive switching of the Cr-doped SrZrO3 heterostructures in order to gain a better understanding of the underlying mechanism related to trapping and detrapping of charge carriers in the oxide.
EXPERIMENTS Capacitor-like epitaxial thin film stacks of perovskite materials on SrTiO3 (STO) substrates were prepared by pulsed laser deposition (PLD) at a substrate temperature of 700 °C. An SrRuO3 (SRO) film of 40 nm thickness was grown on STO (001) substrates (10 mm×10 mm) as a bottom electrode. Half of the area of the electrode was then masked off prior to the deposition of a Cr-doped SrZrO3 (SZO) layer of thickness 150 nm. Cr doping was at 0.2 at%. Both films were deposited at O2 pressures of ranging from 50 to 150 mTorr. Metal TEs such as Pt, Cu, Ag, Cr, Mg or Ti with a diameter of 300 µm were deposited in a separate chamber by rfsputt
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