Nonvolatile Resistive Memory Switching in Amorphous LaGdO 3 Thin Films
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Nonvolatile Resistive Memory Switching in Amorphous LaGdO3 Thin Films P. Misra, S. P. Pavunny and R. S. Katiyar Department of Physics and Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, PR-00936-8377, USA ABSTRACT Nonvolatile unipolar resistive switching properties of the amorphous LaGdO3 thin films deposited by pulsed laser deposition have been studied. Reliable and repeatable switching of the resistance of LaGdO3 film was obtained between low and high resistance states with nearly constant resistance ratio ~ 106 and non-overlapping switching voltages in the range of ~0.6-0.75 V and 2.5-4 V respectively. The switching between low and high resistance states was attributed to the formation and rupture of conductive filaments using temperature dependent resistance measurements. The current conduction mechanisms of the LaGdO3 film in low and high resistance states were found to follow the Ohmic behavior and Poole-Frenkel emission respectively. The resistance of low and high resistance states of the film remained nearly constant for up to ~ 104 seconds indicating good retention. The observed resistive switching characteristics of LaGdO3 thin films are promising for futuristic nonvolatile memories. INTRODUCTION Recently, there has been a spurt in research activities to develop next generation low power, high speed, rugged, high density and nonvolatile resistive random access memory (RRAM) devices [1]. The memory effect in these devices is realized through switching of the resistance of the device between the two states (high and low) of resistances. Amongst other materials currently being explored for the development of RRAM, lanthanum based amorphous binary and turnery high-k oxides have emerged as potential candidates [2]. These materials already proved to be compatible with CMOS technology also. Furthermore, without the limit of grain size and grain boundary, the devices using homogeneous amorphous films can be fabricated smaller, in accordance with the demand of developing microelectronics. We have recently shown that amorphous LaGdO3 (LGO) a ternary high-k dielectric oxide material with high and linear dielectric constant of ~22, large band gap, good thermal stability, and high crystallization temperature of ~ 1000 °C is promising material for CMOS devices [3]. In this paper we report, to the best of our knowledge for the first time, the growth of RRAM devices based on amorphous thin films of LGO in Pt/ LGO/ Pt stack geometry, their unipolar resistive switching characteristics and associated conduction behaviors in both the low resistance state (LRS) and high resistance states (HRS). We also tried to understand the underlying switching mechanism using temperature-dependent studies of resistance of Pt/LGO/ Pt in LRS and HRS which preliminarily revealed that the unipolar resistive switching in Pt/LGO/ Pt devices comes from the formation and rupture of the conductive filaments formed out of extended point defects in the films such as oxygen vacancies and metallic ions. Details of these stud
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