Studies on Resistive Switching of Cu/Ta2O5/Pt Devices for Non-volatile Memory Application

Abstract

AbstractIn recent times, memory devices based on resistive switching (RS) phenomena in dielectric materials have become a strong contender for the futuristic universal memory. Among other materials being explored for RS application, tantalum pentaoxide (Ta2O5) has emerged as potential candidate due to its large dielectric constant and compatibility with the existing complementary metal-oxide semiconductor process. In view of this, we have studied the resistive switching memory characteristics of Ta2O5 thin film in Cu/Ta2O5/Pt device configuration. About 200 nm thick films of Ta2O5were deposited on platinum-coated silicon (Pt/Si) substrate by Pulsed Laser Deposition (PLD) method. On the top of Ta2O5 thin film, Cu electrodes of radius ~100 µm and thickness ~ 100nm were grown by RF magnetron sputtering using shadow masking. The RS behaviour of Cu/Ta2O5/Pt devices was studied by current–voltage (I-V) measurements at room temperature. The as-fabricated Cu/Ta2O5/Pt devices showed repeatable and reliable, non-volatile bipolar resistance switching for 100 cycles, indicating good endurance. Due to virgin low resistance state of the device, the initial electroforming step was not required for bipolar RS. The mean resistance of high resistance state (HRS) and low resistance state (LRS) was ~300 MΩ and 500 Ω respectively with very high resistance ratio of ~106. The Cu/Ta2O5/Pt devices showed good data retention up to 103 s. The resistive switching mechanism in Cu/Ta2O5/Pt devices was understood in terms of redox reaction based formation and rupturing of conducting filaments constituting copper ions. The conduction mechanism in LRS was explained on the basis of Ohmic conduction, whereas Schottky emission and space charge limited conduction (SCLC) were found as possible conduction mechanisms in HRS. Our studies clearly show that Ta2O5-based resistive switching devices may have applications in futuristic universal non-volatile memory technology.KeywordsResistive switchingTa2O5 thin filmPulsed Laser Deposition