Browsing by Author "Aluguri, Rakesh"

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Conductive bridge random access memory characteristics of SiCN based transparent device due to indium diffusion
(2018-03-23)
Kumar, Dayanand
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Aluguri, Rakesh
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Chand, Umesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
In this work, the transparent bipolar resistive switching characteristics of a SiCN-based ITO/ SiCN/AZO structure due to In diffusion from ITO is studied. The SiCN based device is found to be 80% transparent in the visible wavelength region. This device, with AZO as both top and bottom electrodes, does not show any RRAM property due to deposition of the high quality O-2-free SiCN film. Replacing the AZO top electrode with ITO in this device results in good resistive switching (RS) characteristics with a high on/off ratio and long retention. Replacing the SiCN film with ZrO2 also results in excellent RS characteristics due to the formation of an oxygen vacancies filament inside the ZrO2 film. A resistance ratio of on/off is found to be higher in the SiCN based device compared to that of the ZrO2 device. Diffusion of In from ITO into the SiCN film on application of high positive voltage during forming can be attributed to the occurrence of RS in the device, which is confirmed by the analyses of energy dispersive spectroscopy and secondary-ion mass spectrometry. This study shows a pathway for the fabrication of CBRAM based transparent devices for non-volatile memory application.
Enhanced charge storage characteristics of nickel nanocrystals embedded flash memory structures
(2013-04-01)
Ray, Sounak K.
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Panda, Debashis
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Aluguri, Rakesh
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Nickel nanocrystals (NCs) embedded flash memory structure with SiO2 tunnelling and pulsed laser deposition grown Al2O3 blocking oxide is reported here. The post-deposition thermal annealing of an ultrathin (approximate to 5nm) nickel film evaporated on thermally grown SiO2 tunnelling barrier has been performed to form the nickel NCs. The formation of tiny nickel NCs is confirmed from the high-resolution transmission electron microscope micrographs. The electrical capacitancevoltage (CV) characteristics of the optimised 1000 degrees C, 5min annealed sample shows a large memory window of 20V at +/- 20V sweeping voltage. The charge storage properties are found to be significantly improved as compared to control samples. The frequency dependent CV measurements indicate the dominant charge trapping in Ni NCs, making the memory structure attractive for use in future nanoscale high-performance applications.
Enhancement of resistive switching properties in nitride based CBRAM device by inserting an Al2O3 thin layer
(2017-05-15)
Kumar, Dayanand
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Aluguri, Rakesh
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Chand, Umesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
In this letter, we propose a method to enhance resistive switching properties in SiCN-based conductive-bridge resistive switching memory (CBRAM) devices by inserting a thin Al2O3 layer between the SiCN resistive switching layer and the TiN bottom electrode. Compared with the Cu/Ta/SiCN/TiN single-layer device, the Cu/Ta/SiCN/Al2O3/TiN double layer device exhibits uniform resistive switching, long stable endurance cycles (>1.6 x 10(4)), and stable retention (10(4)s) at 125 degrees C. These substantial improvements in the resistive switching properties are attributed to the location of the formation and rupture of conductive filaments that can be precisely controlled in the device after introducing the Al2O3 layer. Moreover, a multilevel resistive switching characteristic is observed in the Cu/Ta/SiCN/Al2O3/TiN double layer CBRAM device. The distinct six-level resistance states are obtained in double layer devices by varying the compliance current. The highly stable retention characteristics (>10(4)) of the Cu/Ta/SiCN/Al2O3/TiN double layer device with multilevel resistance states are also demonstrated. Published by AIP Publishing.
High Performance Bipolar Resistive Switching Characteristics in SiO2/ZrO2/SiO2 Tri-layer Based CBRAM Device
(2017-01-01)
Kumar, Dayanand
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Aluguri, Rakesh
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Chand, Umesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
The bipolar resistive switching properties of the CBRAM device are investigated for nonvolatile memory applications in a SiO2/ZrO2/SiO2 structure. The device shows good switching characteristics with set/reset voltages less than +1 V/-1 V with a variation of less than 0.2 V. The SiO2/ZrO2/SiO2 tri-layer CBRAM device exhibits excellent memory performances, such as stable DC endurance up to 10(3) cycles during the test without degradation, good retention ability (>10(4) s) at a temperature of 100 degrees C with more than 10(2) on/off resistance ratio.
One Bipolar Selector-One Resistor for Flexible Crossbar Memory Applications
(2019-03-01)
Kumar, Dayanand
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Aluguri, Rakesh
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Chand, Umesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
A bipolar, highly nonlinear n-p-n selector is coupled in series with resistive switching memory device to suppress the sneak path current. The memory characteristics are measured for the crossbar array fabricated on a flexible polyethylene terephthalate substrate. Dominant conduction mechanism is the Zener tunneling to obtain the high nonlinearity in the selector device. This phenomenon validates the I-V characteristics which are temperature dependent, which leads to decrease in the turn-on voltage of the device as the temperature increases. The proposed one bipolar selector-one resistor device demonstrates better memory characteristics with the high nonlinearity (similar to 10(3)), observable memory window of about one order, excellent ac endurance (10(7)) cycles, fast switching speed (60 ns), and stable retention (10(4) s) at 100 degrees C. The results show the substantial potential of the proposedone selector-one-resistor structure in suppressing the leakage current, making it attractive for future high-density flexible crossbar memory array.
Overview of Selector Devices for 3-D Stackable Cross Point RRAM Arrays
(2016-09-01)
Aluguri, Rakesh
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Tseng, Tseung-Yuen
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交大名義發表
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National Chiao Tung University
Cross point RRAM arrays is the emerging area for future memory devices due to their high density, excellent scalability. Sneak path problem is the main disadvantage of cross point structures which needed to be overcome to produce real devices. Various self-rectifying cells like complementary resistive cell, hybrid RRAM cell, valence modulated conductive oxide RRAM and non-linear resistive memory with tunneling barrier, etc., are proposed to overcome the sneak path problem and to achieve the high density with good on/off ratio. However, it is challenging to fabricate the self-rectifying cells operating at low program/erase voltages with high non-linearity for both read and write operations and exhibiting good retention and endurance characteristics at the same time for a single device. 1S1R devices are more attractive than SRC due to large optimization possibilities to obtain better device performance as they have separate selector cell and memory cell which decouples the control parameters. Various kinds of selector devices like Si-based selector, metal-oxide based selector, threshold switch selector, mixed ionic-electronic conduction selector etc., are under intense research to obtain the best performance cross point memory devices. In this paper, we have briefly discussed about recent progress on various self-rectifying cells and selector devices for obtaining 3-D stackable cross point memory arrays.
Role of Al2O3 thin layer on improving the resistive switching properties of Ta5Si3-based conductive bridge random accesses memory device
(2018-04-01)
Kumar, Dayanand
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Aluguri, Rakesh
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Chand, Umesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
Ta5Si3-based conductive bridge random access memory (CBRAM) devices have been investigated to improve their resistive switching characteristics for their application in future nonvolatile memory technology. Changes in the switching characteristics by the addition of a thin Al2O3 layer of different thicknesses at the bottom electrode interface of a Ta5Si3-based CBRAM devices have been studied. The double-layer device with a 1 nm Al2O3 layer has shown improved resistive switching characteristics over the single layer one with a high on/off resistance ratio of 10(2), high endurance of more than 10(4) cycles, and good retention for more than 10(5) s at the temperature of 130 degrees C. The higher thermal conductivity of Al2O3 over Ta5Si3 has been attributed to the enhanced switching properties of the double-layer devices. (C) 2018 The Japan Society of Applied Physics.
The impact of TiW barrier layer thickness dependent transition from electro-chemical metallization memory to valence change memory in ZrO2-based resistive switching random access memory devices
(2018-08-30)
Chandrasekaran, Sridhar
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Simanjuntak, Firman Mangasa
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Aluguri, Rakesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
The effect of TiW metal barrier layer thickness on voltage-current characteristics of the Cu/TiW/ZrO2/TiN conductive bridge random access memory device was systematically investigated. The change of reset behavior from abrupt decrease to gradual decrease with increasing TiW thickness was observed. Electronic conduction during the forming process was also analyzed to obtain detailed information about the effect of TiW layer thickness on the nature of the conduction phenomenon. The temperature coefficient of resistance of the conductive filament confirms that an electro-chemical metallization (ECM) based conduction was observed in the devices made with a thinner TiW layer. On the other hand, valence change memory (VCM) based conduction was observed with a thick TiW layer. A conduction mechanism is proposed to explain the ECM to VCM conduction transformation phenomenon.