Subrata Biswas

Associate Professor of Electrical Engineering Department
Electrical Engineering Department Netaji Subhash Engineering College, Technocity Garia, Kolkata – 700 152

Subrata Biswas (SM’12) was born in Kolkata, India in 1978. He received the B.E. degree from Burdwan University, Burdwan, India in 2002 and the M.E.E and PhD (Engineering) degree from Jadavpur University, Kolkata, India in 2006 and 2017 respectively. Currently, he is an Associate Professor in the Electrical Engineering Department, Netaji Subhash Engineering College, Kolkata, has published more than 10 research papers. His research includes the data acquisition and advanced signal processing technique in power system & high voltage Engineering and Partial discharge diagnostics.


Ph.D. (Engg.)


Data acquisition and advanced signal processing technique in power system & high voltage Engineering and Partial discharge diagnostics.


Development of an Intelligent, Low-Cost Partial Discharge (PD) Detection System

This project primarily involves the measurement of partial discharge signals from test object and pattern recognition of those signals so as to determine the type of defect and the condition of the insulation. These days dry type systems are taking over most of the high voltage systems including power sectors. The most important aspect related to dry type system is the problem of partial discharge, as it degrades and reduces the insulation life.

Applications Invited

Scopus Publications

Scopus Publications

  • High Aspect-ratio Germanium-Tin Alloy Nanowires: Potential as Highly Efficient Li-Ion Battery Anodes
    Adrià Garcia‐Gil, Subhajit Biswas, David McNulty, Ahin Roy, Kevin M. Ryan, Valeria Nicolosi, and Justin D. Holmes

    Here, the fabrication of a high aspect ratio (>440) Ge1−xSnx nanowires with super‐thin (≈9 nm) diameter, much below the Bohr radius, using a simple solvothermal‐like growth method under supercritical toluene conditions at a reaction temperature of 440 °C is reported. Ge1−xSnx nanowires are grown with varying amounts of Sn in Ge lattice, between 3.1 to 10.2 at%. The growth of the Ge1−xSnx alloy nanowires is achieved without any additional catalysts, and directly on current collector substrates (titanium) for application as Li‐ion battery anodes. The electrochemical performance of the binder‐free Ge1−xSnx nanowires as an anode material for Li‐ion batteries is investigated via galvanostatic cycling and detailed analysis of differential capacity plots. The dimensions of the nanowires, and the amount of Sn in Ge, are critical to achieving a high specific capacity and capacity retention. Ge1−xSnx nanowires with the highest aspect ratios and with the lowest Sn content (3.1 at%) demonstrate exceptional capacity retention of ≈90% and 86% from the 10th to the 100th and 150th cycles respectively, while maintaining a very high specific capacity value of 1176 and 1127 mAh g−1 after the 100 and 150 cycles respectively.

  • Lattice dynamics of Ge<inf>1−x</inf>Sn<inf>x</inf> alloy nanowires
    Sreyan Raha, Subhajit Biswas, Jessica Doherty, Prasanna Kumar Mondal, Justin D. Holmes, and Achintya Singha

    Royal Society of Chemistry (RSC)
    Alloying group IV semiconductors offers an effective way to engineer their electronic properties and lattice dynamics.

  • Solution phase growth and analysis of super-thin zigzag tin selenide nanoribbons
    Fionán Davitt, Kamil Rahme, Sreyan Raha, Shane Garvey, Manuel Roldan-Gutierrez, Achintya Singha, Shery L Y Chang, Subhajit Biswas, and Justin D Holmes

    IOP Publishing
    Abstract Tin selenide (SnSe), a highly promising layered material, has been garnering particular interest in recent times due to its significant promise for future energy devices. Herein we report a simple solution-phase approach for growing highly crystalline layered SnSe nanoribbons. Polyvinylpyrrolidone (PVP) was used as a templating agent to selectively passivates the (100) and (001) facets of the SnSe nanoribbons resulting in the unique growth of nanoribbons along their b-axis with a defined zigzag edge state along the sidewalls. The SnSe nanoribbons are few layers thick (∼20 layers), with mean widths of ∼40 nm, and achievable length of &gt;1 μm. Nanoribbons could be produced in relatively high quantities (&gt;150 mg) in a single batch experiment. The PVP coating also offers some resistance to oxidation, with the removal of the PVP seen to lead to the formation of a SnSe/SnO x core-shell structure. The use of non-toxic PVP to replace toxic amines that are typically employed for other 1D forms of SnSe is a significant advantage for sustainable and environmentally friendly applications. Heat transport properties of the SnSe nanoribbons, derived from power-dependent Raman spectroscopy, demonstrate the potential of SnSe nanoribbons as thermoelectric material.

  • Erratum: Probing lattice dynamics in ST 12 phase germanium nanowires by Raman spectroscopy (Appl. Phys. Lett. (2021) 119 (232105) DOI: 10.1063/5.0066744)
    Sreyan Raha, Divya Srivastava, Subhajit Biswas, Adrià Garcia-Gil, Antti J. Karttunen, Justin D. Holmes, and Achintya Singha

    AIP Publishing

  • One-Step Grown Carbonaceous Germanium Nanowires and Their Application as Highly Efficient Lithium-Ion Battery Anodes
    Adrià Garcia, Subhajit Biswas, David McNulty, Ahin Roy, Sreyan Raha, Sigita Trabesinger, Valeria Nicolosi, Achintya Singha, and Justin D. Holmes

    American Chemical Society (ACS)
    Developing a simple, cheap, and scalable synthetic method for the fabrication of functional nanomaterials is crucial. Carbon-based nanowire nanocomposites could play a key role in integrating group IV semiconducting nanomaterials as anodes into Li-ion batteries. Here, we report a very simple, one-pot solvothermal-like growth of carbonaceous germanium (C-Ge) nanowires in a supercritical solvent. C-Ge nanowires are grown just by heating (380–490 °C) a commercially sourced Ge precursor, diphenylgermane (DPG), in supercritical toluene, without any external catalysts or surfactants. The self-seeded nanowires are highly crystalline and very thin, with an average diameter between 11 and 19 nm. The amorphous carbonaceous layer coating on Ge nanowires is formed from the polymerization and condensation of light carbon compounds generated from the decomposition of DPG during the growth process. These carbonaceous Ge nanowires demonstrate impressive electrochemical performance as an anode material for Li-ion batteries with high specific charge values (>1200 mAh g–1 after 500 cycles), greater than most of the previously reported for other “binder-free” Ge nanowire anode materials, and exceptionally stable capacity retention. The high specific charge values and impressively stable capacity are due to the unique morphology and composition of the nanowires.

  • Growth and analysis of the tetragonal (ST12) germanium nanowires
    Adrià Garcia-Gil, Subhajit Biswas, Ahin Roy, Dzianis Saladukh, Sreyan Raha, Thomas Blon, Michele Conroy, Valeria Nicolosi, Achintya Singha, Lise-Marie Lacroix,et al.

    Royal Society of Chemistry (RSC)
    A simple method was developed to synthesize ST12 germanium nanowires at moderate temperatures and pressure in a supercritical toluene atmosphere. Efficient light emission was observed from this Ge allotrope.

  • Probing lattice dynamics in ST 12 phase germanium nanowires by Raman spectroscopy
    Sreyan Raha, Divya Srivastava, Subhajit Biswas, Adrià Garcia-Gil, Antti J. Karttunen, Justin D. Holmes, and Achintya Singha

    AIP Publishing

  • A review of self-seeded germanium nanowires: Synthesis, growth mechanisms and potential applications
    Adrià Garcia-Gil, Subhajit Biswas, and Justin D. Holmes

    Ge nanowires are playing a big role in the development of new functional microelectronic modules, such as gate-all-around field-effect transistor devices, on-chip lasers and photodetectors. The widely used three-phase bottom-up growth method utilising a foreign catalyst metal or metalloid is by far the most popular for Ge nanowire growth. However, to fully utilise the potential of Ge nanowires, it is important to explore and understand alternative and functional growth paradigms such as self-seeded nanowire growth, where nanowire growth is usually directed by the in situ-formed catalysts of the growth material, i.e., Ge in this case. Additionally, it is important to understand how the self-seeded nanowires can benefit the device application of nanomaterials as the additional metal seeding can influence electron and phonon transport, and the electronic band structure in the nanomaterials. Here, we review recent advances in the growth and application of self-seeded Ge and Ge-based binary alloy (GeSn) nanowires. Different fabrication methods for growing self-seeded Ge nanowires are delineated and correlated with metal seeded growth. This review also highlights the requirement and advantage of self-seeded growth approach for Ge nanomaterials in the potential applications in energy storage and nanoelectronic devices.

  • Structural evolution of nanophase separated block copolymer patterns in supercritical co2
    Tandra Ghoshal, Timothy W. Collins, Subhajit Biswas, Michael A. Morris, and Justin D. Holmes

    Nanopatterns can readily be formed by annealing block copolymers (BCPs) in organic solvents at moderate or high temperatures. However, this approach can be challenging from an environmental and industrial point of view. Herein, we describe a simple and environmentally friendly alternative to achieve periodically ordered nanoscale phase separated BCP structures. Asymmetric polystyrene-b-poly(ethylene oxide) (PS-b-PEO) thin film patterns of different molecular weight were achieved by annealing in supercritical carbon dioxide (sc-CO2). Microphase separation of PS-b-PEO (16,000–5000) film patterns were achieved by annealing in scCO2 at a relatively low temperature was previously reported by our group. The effects of annealing temperature, time and depressurisation rates for the polymer system were also discussed. In this article, we have expanded this study to create new knowledge on the structural and dimensional evolution of nanohole and line/space surface periodicity of four other different molecular weights PS-b-PEO systems. Periodic, well defined, hexagonally ordered films of line and hole patterns were obtained at low CO2 temperatures (35–40 °C) and pressures (1200–1300 psi). Further, the changes in morphology, ordering and feature sizes for a new PS-b-PEO system (42,000–11,500) are discussed in detail upon changing the scCO2 annealing parameters (temperature, film thickness, depressurization rates, etc.). In relation to our previous reports, the broad annealing temperature and depressurisation rate were explored together for different film thicknesses. In addition, the effects of SCF annealing for three other BCP systems (PEO-b-PS, PS-b-PDMS, PS-b-PLA) is also investigated with similar processing conditions. The patterns were also generated on a graphoepitaxial substrate for device application.

  • Stretching the Equilibrium Limit of Sn in Ge<inf>1- x</inf>Sn<inf>x</inf>Nanowires: Implications for Field Effect Transistors
    Subhajit Biswas, Jessica Doherty, Emmanuele Galluccio, Hugh G. Manning, Michele Conroy, Ray Duffy, Ursel Bangert, John J. Boland, and Justin D. Holmes

    American Chemical Society (ACS)
    Ge1–xSnx nanowires incorporating a large amount of Sn would be useful for mobility enhancement in nanoelectronic devices, a definitive transition to a direct bandgap for application in optoelectronic devices and to increase the efficiency of the GeSn-based photonic devices. Here we report the catalytic bottom-up fabrication of Ge1–xSnx nanowires with very high Sn incorporation (x > 0.3). These nanowires are grown in supercritical toluene under high pressure (21 MPa). The introduction of high pressure in the vapor–liquid–solid (VLS) like growth regime resulted in a substantial increase of Sn incorporation in the nanowires, with a Sn content ranging between 10 and 35 atom %. The incorporation of Sn in the nanowires was found to be inversely related to nanowire diameter; a high Sn content of 35 atom % was achieved in very thin Ge1–xSnx nanowires with diameters close to 20 nm. Sn was found to be homogeneously distributed throughout the body of the nanowires, without apparent clustering or segregation. The large inclusion of Sn in the nanowires could be attributed to the nanowire growth kinetics and small nanowire diameters, resulting in increased solubility of Sn in Ge at the metastable liquid–solid interface under high pressure. Electrical investigation of the Ge1–xSnx (x = 0.10) nanowires synthesized by the supercritical fluid approach revealed their potential in nanoelectronics and sensor-based applications.

  • Directly Grown Germanium Nanowires from Stainless Steel: High-performing Anodes for Li-Ion Batteries
    David McNulty, Subhajit Biswas, Shane Garvey, Colm O’Dwyer, and Justin D. Holmes

    American Chemical Society (ACS)

  • Probing dipole and quadrupole resonance mode in non-plasmonic nanowire using Raman spectroscopy
    Sreyan Raha, Sreemanta Mitra, Prasanna Kumar Mondal, Subhajit Biswas, Justin D Holmes, and Achintya Singha

    IOP Publishing
    Electric field enhancement in semiconductor nanostructures offers a possibility to find an alternative to the metallic particles which is well known for tuning the light-matter interaction due to its strong polarizability and size-dependent surface plasmon resonance energy. Raman spectroscopy is a powerful technique to monitor the electric field as its scattering depends on the electromagnetic eigenmode of the particle. Here, we observe enhanced polarized Raman scattering from germanium nanowires of different diameters. The incident electromagnetic radiation creates a distribution of the internal electric field inside the naowires which can be enhanced by manipulating the nanowire diameter, the incident electric field and its polarization. Our estimation of the enhancement factor, including its dependence on nanowire diameter, agrees well with the Mie theory for an infinite cylinder. Furthermore, depending on diameter and wavelength of incident radiation, polarized Raman study shows dipolar (antenna effect) and quadrupolar resonances, which has never been observed in germanium nanowire. We attempt to understand this polarized Raman behavior using COMSOL Multiphysics simulation, which suggests that the pattern observed is due to photon confinement within the nanowires. Thus, the light scattering direction can be toggled by tuning the polarization of incident excitation and diameter of non plasmonic nanowire.

  • Crystallographically Controlled Synthesis of SnSe Nanowires: Potential in Resistive Memory Devices
    Fionán Davitt, Hugh G. Manning, Fred Robinson, Samantha L. Hawken, Subhajit Biswas, Nikolay Petkov, Maart Druenen, John J. Boland, Gillian Reid, and Justin D. Holmes

    Here the controlled growth of SnSe nanowires by a liquid injection chemical vapor deposition (CVD) method employing a distorted octahedral [SnCl4{nBuSe(CH2)3SenBu}] single‐source diselenoether precursor is reported. CVD with this single‐source precursor allows morphological and compositional control of the SnSex nanostructures formed, including the transformation of SnSe2 nanoflakes into SnSe nanowires and again to SnSe nanoflakes with increasing growth temperature. Significantly, highly crystalline SnSe nanowires with an orthorhombic Pnma 62 crystal structure can be controllably synthesized in two growth directions, either <011> or <100>. The ability to tune the growth direction of SnSe will have important implications for devices constructed using these nanocrystals. The SnSe nanowires with a <011> growth direction display a reversible polarity‐dependent memory switching ability, not previously reported for nanoscale SnSe. A resistive switching on/off ratio of 103 without the use of a current compliance limit is seen, illustrating the potential use of SnSe nanowires for low‐power nonvolatile memory applications.

  • Ultrahigh Negative Infrared Photoconductance in Highly As-Doped Germanium Nanowires Induced by Hot Electron Trapping
    John Wellington John, Veerendra Dhyani, Yordan M. Georgiev, Anushka S. Gangnaik, Subhajit Biswas, Justin D. Holmes, Amit K. Das, Samit K. Ray, and Samaresh Das

    American Chemical Society (ACS)
    Here, we report the observation of negative photoconductance (NPC) effect in highly arsenic-doped germanium nanowires (Ge NWs) for the infrared light. NPC was studied by light-assisted Kelvin probe...

  • Two-Dimensional SnSe Nanonetworks: Growth and Evaluation for Li-Ion Battery Applications
    Fionán Davitt, Killian Stokes, Timothy W. Collins, Manuel Roldan-Gutierrez, Fred Robinson, Hugh Geaney, Subhajit Biswas, Shery L.Y. Chang, Kevin M. Ryan, Gillian Reid,et al.

    American Chemical Society (ACS)
    Engineered two-dimensional (2D) layered materials possess unique physical properties with the potential to improve the performance and endurance of future electronic and energy devices. Here, we report the growth of complex 2D nanonetworks of crystalline tin selenide (SnSe) via liquid injection chemical vapor deposition using a single-source diselenoether precursor. Potential applications of SnSe span a wide range of technological areas, particularly in energy devices. The synthesized SnSe networks were composed of high surface area interconnected junctions of one-dimensional (1D) nanowires in a 2D plane; such complex SnSe nanonetwork structures have not previously been reported. The SnSe networks possessed an orthorhombic Pnma 62 crystal structure throughout, with the individual network branches uniformly orientated along the and directions. The width of the individual interconnected nanowire branches ranged from 120 to 250 nm with lengths ranging from 1 to 4 μm. The networks of 1D nanowires had a layer thickness of 88 ± 10 nm. A growth mechanism for the formation of these networks is proposed based on the minimization of high surface energy planes. We also highlight the potential of SnSe nanonetworks as an anode material for Li-ion batteries with galvanostatic testing showing an initial discharge capacity in excess of 1000 mAh g–1 with a 92% capacity retention after 50 cycles at a specific current of 100 mA g–1.

  • Progress on Germanium-Tin Nanoscale Alloys
    Jessica Doherty, Subhajit Biswas, Emmanuele Galluccio, Christopher A. Broderick, Adria Garcia-Gil, Ray Duffy, Eoin P. O’Reilly, and Justin D. Holmes

    American Chemical Society (ACS)
    Group IV alloys have attracted interest in the drive to create Si compatible, direct bandgap materials for implementation in complementary metal oxide semiconductor (CMOS) and beyond CMOS devices. ...

  • Field-Effect Transistor Figures of Merit for Vapor-Liquid-Solid-Grown Ge<inf>1-x</inf>Sn <inf>x</inf>(x = 0.03-0.09) Nanowire Devices
    Emmanuele Galluccio, Jessica Doherty, Subhajit Biswas, Justin D. Holmes, and Ray Duffy

    American Chemical Society (ACS)
    Ge1-xSnx alloys form a heterogeneous material system with high potential for applications in both optoelectronic and high-speed electronics devices. The attractiveness of Ge1-xSnx lies in the abili...

  • Germanium tin alloy nanowires as anode materials for high performance Li-ion batteries
    Jessica Doherty, David McNulty, Subhajit Biswas, Kalani Moore, Michele Conroy, Ursel Bangert, Colm O’Dwyer, and Justin D Holmes

    IOP Publishing
    The combination of two active Li-ion materials (Ge and Sn) can result in improved conduction paths and higher capacity retention. Here we report for the first time, the implementation of Ge1–xSnx alloy nanowires as anode materials for Li-ion batteries. Ge1−xSnx alloy nanowires have been successfully grown via vapor–liquid–solid technique directly on stainless steel current collectors. Ge1−xSnx (x = 0.048) nanowires were predominantly seeded from the Au0.80Ag0.20 catalysts with negligible amount of growth was also directly catalyzed from stainless steel substrate. The electrochemical performance of the the Ge1−xSnx nanowires as an anode material for Li-ion batteries was investigated via galvanostatic cycling and detailed analysis of differential capacity plots (DCPs). The nanowire electrodes demonstrated an exceptional capacity retention of 93.4% from the 2nd to the 100th charge at a C/5 rate, while maintaining a specific capacity value of ∼921 mAh g−1 after 100 cycles. Voltage profiles and DCPs revealed that the Ge1−xSnx nanowires behave as an alloying mode anode material, as reduction/oxidation peaks for both Ge and Sn were observed, however it is clear that the reversible lithiation of Ge is responsible for the majority of the charge stored.

  • Investigating the mechanical properties of GeSn nanowires
    Jelena Kosmaca, Raimonds Meija, Mikk Antsov, Gunta Kunakova, Raitis Sondors, Igor Iatsunskyi, Emerson Coy, Jessica Doherty, Subhajit Biswas, Justin D. Holmes,et al.

    Royal Society of Chemistry (RSC)
    Mechanical resonance and bending tests on crystalline GeSn nanowires revealed size-dependent Young's moduli and bending strengths close to theoretical values.

  • Resonance assisted jump-in voltage reduction for electrostatically actuated nanobeam-based gateless NEM switches
    R Meija, A I Livshits, J Kosmaca, L Jasulaneca, J Andzane, S Biswas, J D Holmes, and D Erts

    IOP Publishing
    Electrostatically actuated nanobeam-based electromechanical switches have shown promise for versatile novel applications, such as low power devices. However, their widespread use is restricted due to poor reliability resulting from high jump-in voltages. This article reports a new method for lowering the jump-in voltage by inducing mechanical oscillations in the active element during the switching ON process, reducing the jump-in voltage by more than three times. Ge0.91Sn0.09 alloy and Bi2Se3 nanowire-based nanoelectromechanical switches were constructed in situ to demonstrate the operation principles and advantages of the proposed method.

  • Neuromorphic- Inspired Behaviour in Core-Shell Nanowire Networks
    Hugh G. Manning, Subhajit Biswas, Shailja Kumar, Justin D. Holmes, and John J. Boland

    Abstrac t-Enginee ring smart-material s with emerge nt properti es requires designi ng and characte rizing systems with desirabl e behavio urs. Neurom orphic (brain-like) architectures require plasticity, where the strength of the connections and the time with which they decay can be modulated based on the magnitude and the repetition of the applied stimuli. This functionality is emulated in our complex nanowire network material through electrical resistive switching. The formation of nano-sized filamentary connections between overlapping wires across the network facilitates a controllable transition from a high resistance state to one (or more) lower resistance states with corresponding memory retention times. We report on the neuromorphic inspired behaviors that emerge from networks of metal nanowires coated with TiO2 shells.

  • One-Step Fabrication of GeSn Branched Nanowires
    Jessica Doherty, Subhajit Biswas, David McNulty, Clive Downing, Sreyan Raha, Colm O’Regan, Achintya Singha, Colm O’Dwyer, and Justin D. Holmes

    American Chemical Society (ACS)
    We report for the first time the self-catalyzed, single-step growth of branched GeSn nanostructures by a vapor–liquid–solid mechanism. These typical GeSn nanostructures consist of ⟨111⟩-oriented, Sn-rich (∼8 atom %) GeSn “branches” grown epitaxially on GeSn “trunks”, with a Sn content of ∼4 atom %. The trunks were seeded from Au0.80Ag0.20 nanoparticles followed by the catalytic growth of secondary branches (diameter ∼ 50 nm) from the excess of Sn on the sidewalls of the trunks, as determined by high-resolution electron microscopy and energy-dispersive X-ray analysis. The nanowires, with ⟨111⟩-directed GeSn branches oriented at ∼70° to the trunks, have no apparent defects or change in crystal structure at the trunk–branch interface; structural quality is retained at the interface with epitaxial crystallographic relation. The electrochemical performance of these highly ordered GeSn nanostructures was explored as a potential anode material for Li-ion batteries, due to their high surface-to-volume ratio and i...

  • Emergence of winner-takes-all connectivity paths in random nanowire networks
    Hugh G. Manning, Fabio Niosi, Claudia Gomes da Rocha, Allen T. Bellew, Colin O’Callaghan, Subhajit Biswas, Patrick F. Flowers, Benjamin J. Wiley, Justin D. Holmes, Mauro S. Ferreira,et al.

    Springer Science and Business Media LLC
    AbstractNanowire networks are promising memristive architectures for neuromorphic applications due to their connectivity and neurosynaptic-like behaviours. Here, we demonstrate a self-similar scaling of the conductance of networks and the junctions that comprise them. We show this behavior is an emergent property of any junction-dominated network. A particular class of junctions naturally leads to the emergence of conductance plateaus and a “winner-takes-all” conducting path that spans the entire network, and which we show corresponds to the lowest-energy connectivity path. The memory stored in the conductance state is distributed across the network but encoded in specific connectivity pathways, similar to that found in biological systems. These results are expected to have important implications for development of neuromorphic devices based on reservoir computing.

  • Influence of growth kinetics on Sn incorporation in direct band gap Ge<inf>1-x</inf>Sn<inf>x</inf> nanowires
    Jessica Doherty, Subhajit Biswas, Dzianis Saladukha, Quentin Ramasse, Tara Shankar Bhattacharya, Achintya Singha, Tomasz J. Ochalski, and Justin D. Holmes

    Royal Society of Chemistry (RSC)
    An investigation of the influence of growth kinetics on Sn incorporation in Ge1−xSnx nanowires.

  • Nonpolar Resistive Switching in Ag@TiO<inf>2</inf> Core-Shell Nanowires
    Hugh G. Manning, Subhajit Biswas, Justin D. Holmes, and John J. Boland

    American Chemical Society (ACS)
    Nonpolar resistive switching (RS), a combination of bipolar and unipolar RS, is demonstrated for the first time in a single nanowire (NW) system. Exploiting Ag@TiO2 core-shell (CS) NWs synthesized by postgrowth shell formation, the switching mode is controlled by adjusting the current compliance effectively, tailoring the electrical polarity response. We demonstrate ON/OFF ratios of 105 and 107 for bipolar and unipolar modes, respectively. In the bipolar regime, retention times could be controlled up to 103 s, and in the unipolar mode, >106 s was recorded. We show how the unique dual-mode switching behavior is enabled by the defect-rich polycrystalline material structure of the TiO2 shell and the interaction between the Ag core and the Ag electrodes. These results provide a foundation for engineering nonpolar RS behaviors for memory storage and neuromorphic applications in CSNW structures.