Unipolar resistive switching behavior of high-k ternary rare-earth oxide LaHoO 3 thin films for non-volatile memory appl
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Unipolar resistive switching behavior of high-k ternary rare-earth oxide LaHoO3 thin films for non-volatile memory applications Yogesh Sharma, Pankaj Misra, Shojan P. Pavunny, and Ram S. Katiyar Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico, PR-00936-8377, USA
ABSTRACT Rare-earth oxides have attracted considerable research interest in resistive random access memories (ReRAMs) due to their compatibility with complementary metal-oxide semiconductor (CMOS) process. To this end we report unipolar resistive switching in a novel ternary rare-earth oxide LaHoO3 (LHO) to accelerate progress and to support advances in this emerging densely scalable research architecture. Amorphous thin films of LHO were fabricated on Pt/TiO2/SiO2/Si substrate by pulsed laser deposition, followed by sputter deposition of platinum top electrode through shadow mask in order to elucidate the resistive switching behavior of the resulting Pt/LHO/Pt metal-insulator-metal (MIM) device structure. Stable unipolar resistive switching characteristics with interesting switching parameters like, high resistance ratio of about 105 between high resistance state (HRS) and low resistance state (LRS), non-overlapping switching voltages with narrow dispersion, and excellent retention and endurance features were observed in Pt/LHO/Pt device structure. The observed resistive switching in LHO was explained by the formation/rupture of conductive filaments formed out of oxygen vacancies and metallic Ho atom. From the current-voltage characteristics of Pt/LHO/Pt structure, the conduction mechanism in LRS and HRS was found to be dominated by Ohm’s law and Poole-Frenkel emission, respectively. INTRODUCTION Simple design, excellent scalability, high switching speed, and compatibility with complementary metal–oxide–semiconductor process make resistive random access memory (ReRAM) a potential candidate for nonvolatile data storage [1-3]. Some rare-earth oxides showed electrical field induced change of resistivity where the presence of two different resistance states namely a high-resistance state (OFF-state) and a low-resistance state (ON-state) serve as the basis of memory storage [4]. Rare-earth oxide-based ReRAM with the features of stable non-volatile unipolar and/or bipolar resistive switching has been proposed for the embedded application including multi-level storage capability and excellent reliability [4]. Generally, the resistive switching (RS) mechanism in rare-earth oxides based ReRAM device can be explained by the well-accepted conductive filamentary model where several nanometersized filaments are formed by the agglomeration of existing or field induced chemical defects (i.e., metallic rare-earths and oxygen vacancies) during the electro-forming process [4-6]. Recently, we reported nonvolatile multilevel resistive memory behavior in thin films of one of the ternary rare-earth oxides SmGdO3 (SGO) [7]. The stable 4-level resistance states of the Pt/SGO/Pt device with sufficient margin of resistance ratios (ON/OFF)
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