Publications | Nanodevice Research

Publication Highlights

1. Karthik Krishnan, Shaikh Mohammad Tauquir, Saranyan Vijayaraghavan, and Ramesh Mohan, “Configurable Switching Behavior in Polymer-based Resistive Memories by Adopting Unique Electrode/Electrolyte Arrangement” RSC Advances. 2021.

Abstract: The difference in resistive switching characteristics by modifying the device configuration provides a unique operating principle, which is essential for both fundamental studies and the development of future memory devices. In this work, we demonstrate the poly(methyl methacrylate) (PMMA)-based resistive switching characteristics using four different combinations of electrode/electrolyte arrangement in the device geometry. Significantly, the current conduction in the filament and resistive switching behavior depend majorly on the presence of Al electrode and electrochemically active silver (Ag) element in the PMMA matrix. The depth-profiling X-ray photoelectron spectroscopy (XPS) study evidences the conducting filament formation processes in the PMMA-based devices. These results with different conduction mechanisms provide further insights into the understanding of the resistive switching behavior in the polymer-based devices by simply rearranging the device configuration.

2. Karthik Krishnan, Selvakumar Karuthapandi, and Saranyan Vijayaraghavan, “Ionic Transport Kinetics and Enhanced Energy Storage in the Electrode/Poly(N‑vinyl imidazole) Interface for Micro-Supercapacitors” RSC Adv., 2020,10, 45019-45027.

Abstract: A detailed understanding and controlling of ionic transport pathways in the electrode/electrolyte interface is vital for realizing micro-scale energy storage devices and formulating adequate design principles. Planar device geometry with nanostructured thin solid polymer electrolyte (SPE) in which the potassium hydroxide (KOH) incorporated poly(N-vinyl imidazole) (PVI) is demonstrated for micro-supercapacitors (MSCs). The adsorption/desorption kinetics of ionic charges in the interfacial regime of ITO/PVI-KOH has been investigated for electrical double layer capacitance (EDLC) characteristics. . The electrochemical property of planar MSC has been systematically studied so as to ensure how the anions and cations are separated at electrode/electrolyte interfaces by means of an electromotive force. Significantly, the hydrated PVI enables charge migration and separation of cations and anions at the electrode/electrolyte interfaces.

3. Karthik Krishnan, Masakazu Aono, Kazuya Terabe, and Tohru Tsuruoka, “Significant roles of the polymer matrix in the resistive switching behavior of polymer-based atomic switches" J. Phys. D: Appl. Phys. 2019, 52 445301.

Abstract: The impacts of the polymer matrix material on the resistive switching of solid polymer electrolyte (SPE)-based memory devices are investigated. The resistive devices consist of a SPE film using silver salt incorporated polyethylene oxide, polyvinyl alcohol, or polyvinyl pirrolydone, which is sandwiched between Ag and Pt electrodes. The switching characteristics depend strongly on the structural, thermal, and transport properties of the polymer matrix, such as its crystallinity, glass transition temperature, and ionic conductivity. The temperature behavior of resistive switching can be explained by competition between increased segmental mobility and water evaporation in the polymer matrix. It is found that crystalline and semicrystalline polymer electrolytes are likely to perform better than amorphous polymer electrolytes in realizing stable switching characteristics.

4. Karthik Krishnan, Premkumar Jayaraman, Subramanian Balasubramanian, and Ulaganathan Mani, “Nanoionic Transport and Electric Double Layer Formation at the Electrode/Polymer Interface for High Performance Supercapacitors” J. Mat. Chem. A. 2018, 6, 23650-23658.

Abstract: The impacts of the polymer matrix material on the resistive switching of solid polymer electrolyte (SPE)-based memory devices are investigated. The resistive devices consist of a SPE film using silver salt incorporated polyethylene oxide, polyvinyl alcohol, or polyvinyl pirrolydone, which is sandwiched between Ag and Pt electrodes. The switching characteristics depend strongly on the structural, thermal, and transport properties of the polymer matrix, such as its crystallinity, glass transition temperature, and ionic conductivity. The temperature behavior of resistive switching can be explained by competition between increased segmental mobility and water evaporation in the polymer matrix. It is found that crystalline and semicrystalline polymer electrolytes are likely to perform better than amorphous polymer electrolytes in realizing stable switching characteristics.

5. Karthik Krishnan, Manoharan Muruganathan, Tohru Tsuruoka, Hiroshi Mizuta, and Masakazu Aono “Highly Reproducible and Regulated Conductance Quantization in a Polymer-Based Atomic Switch” Adv. Funct. Mater. 2017, 27, 1605104

Abstract: The emergence of quantized conductance states and their correlation with resistive switching characteristics in polymer-based resistive memory devices are investigated using combinations of current–voltage measurements and first-principles density functional theory (DFT) simulations. The well-defined, multiple quantized conductance states observed in these polymer-based resistive switching devices show promise for the development of new multilevel memory devices.

6. Karthik Krishnan, Tohru Tsuruoka, Cedric Mannequin, and Masakazu Aono, “Mechanism for Conducting Filament Growth in Self-Assembled Polymer Thin Films for Redox-Based Atomic Switches” Adv. Mater., Vol. 28, 2016, 640-648.

Abstract: The emergence of quantized conductance states and their correlation with resistive switching characteristics in polymer-based resistive memory devices are investigated using combinations of current–voltage measurements and first-principles density functional theory (DFT) simulations. The well-defined, multiple quantized conductance states observed in these polymer-based resistive switching devices show promise for the development of new multilevel memory devices.

7. Karthik Krishnan, Tohru Tsuruoka, and Masakazu Aono, “Kinetic Factors Determining Conducting Filament Formation in Solid Polymer Electrolyte Based Planar Devices” Nanoscale, Vol. 8, 2016, pp. 13976-13984

Abstract: Resistive switching characteristics and conducting filament formation dynamics in solid polymer electrolyte (SPE) based planar-type resistive switching devices have been investigated by optimizing the device configuration and experimental parameters such as the gap distance between the electrodes, the salt inclusion in the polymer matrix, and the compliance current applied in current–voltage measurements. It was found that switching behaviour and filament growth morphology depend strongly on several kinetic factors, such as the redox reaction rate at the electrode–polymer interfaces, ion mobility in the polymer matrix, electric field strength, and the reduction sites for precipitation.

8. Karthik Krishnan, Hiroko Iwatsuki, Mitsuo Hara, Shusaku Nagano, and Yuki Nagao, “Proton conductivity enhancement in oriented, sulfonated polyimide thin films” J. Mat. Chem. A. Vol. 2, 2014, pp. 6895-6903.

Abstract: Studies of proton transport in confined thin polymer electrolytes are essential for providing additional information regarding the structure–property relationships of such materials. Using a combination of proton transport measurements and structural characterization, we explored the effect of proton conductivity in sulfonated polyimide (SPI) under both bulk and nanostructured thin film systems. In thin films, the preferred chain packing along the in-plane direction can have considerable influence on the charge transport characteristics, which leads to the enhanced proton conductivity. Under high-humidity conditions, the strong interaction between the side-chain sulfonic acid groups and water molecules causes an abrupt change in the internal structure in bulk SPI. Such a structural rearrangement results in a liquid-crystal-like ordered polymer structure.

Selected Publications

Karthik Krishnan, Tohru Tsuruoka, and Masakazu Aono, “Thermally Stable Solid Polymer Electrolyte-based Atomic Switches for High-Temperature Memory Applications” J. Mat. Chem. C. 2018, 6, 6460-6464.

Karthik Krishnan, Manoharan Muruganathan, Tohru Tsuruoka, Hiroshi Mizuta, and Masakazu Aono “Quantized Conductance Operation Near a Single-Atom Point Contact in a Polymer-Based Atomic Switch” Jpn. J. Appl. Phys., 2017, 56, 06GF02.

Yuki Nagao, Karthik Krishnan, Ryosuke Goto, Mitsuo Hara, and Shusaku Nagano, “Effect of Casting Solvent on Interfacial Molecular Structure and Proton Transport Characteristics of Sulfonated Polyimide Thin Films” Anal. Sci. 2017, 33, 35–39. (Selected as Hot article).

Karthik Krishnan, Tohru Tsuruoka, and Masakazu Aono, “Direct observation of anodic dissolution and filament growth behavior in PEO-based atomic switch structures” Jpn. J. Appl. Phys., 2016, 55, 06GK02.

Karthik Krishnan, Hiroko Iwatsuki, Mitsuo Hara, Shusaku Nagano, Keisuke Ohdaira, and Yuki Nagao, “Influence of Molecular Weight on Molecular Ordering and Proton Transport in Organized Sulfonated Polyimide Thin Films”, J. Phys. Chem. C, 2015, 119(38), 21767-21774.

Karthik Krishnan, Tomoki Yamada, Hiroko Iwatsuki, Mitsuo Hara, Shusaku Nagano, Kazuya Otsubo, Osami Sakata, Akihiko Fujiwara, Hiroshi Kitagawa, and Yuki Nagao, “Influence of Confined Polymer Structure on Proton Transport Property in Sulfonated Polyimide Thin Films” Electrochemistry, 2014, 82 (10), 1-5.