Browsing by Author "Thathron, T."

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    Studies on Resistive Switching of Cu/Ta2O5/Pt Devices for Non-volatile Memory Application
    (Springer, 2021) Thathron, T.; Sahu, V.K.; Ajimsha, R.S.; Das, A.K.; Misra, P.
    In 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. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Understanding the coexistence of two bipolar resistive switching modes with opposite polarity in CuxO (1 ≤ x ≤ 2)-based two-terminal devices
    (Springer, 2022) Sterin, N.S.; Thathron, T.; Mal, S.S.; Das, P.P.
    In this work, we have fabricated and tested the resistive switching behavior of non-volatile nature in a number of devices with mainly two architectures: (1) W tip/CuxO/Pt/Ti/SiO2/Si and (2) Cu contact pad/CuxO/Pt/Ti/SiO2/Si. The device type (1) showed coexistence of two bipolar resistive switching modes, commonly known as eight-wise (8w) and counter-eight-wise (c8w), in their current–voltage (I-V) characteristics. We report considerably high ON/OFF ratio of 105 and stable retention time 15 × 103 s. The formation and annihilation of metallic Cu nanofilaments were argued as the plausible reason behind the observed resistive switching events. The onset of quantized conductance steps in the typical conductance plots (in units of quanta of conductance 2e2/h, where e and h are electronic charge and Planck’s constant, respectively) – a phenomenon usually observed in narrow conductive channel – was exploited to provide an “indirect” proof for formation of metallic Cu-based filaments or channels during switching. On the contrary, in device type (2), we observed only “regular” bipolar switching. The operating voltage was less than 1 V in both the devices – suggesting its potential low-power applications. We assessed the underlying conduction mechanism in depth and also theoretically estimated the lateral size of the tiny conductive nanofilaments formed during the switching events. Copper being a cost-effective and widely available substance, our results indicate that CuxO-based cells can be a feasible and useful route for non-volatile resistive memories. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.