A paper titled “Study on ferroelectric polarization induced resistive switching characteristics of neodymium-doped bismuth ferrite thin films for random access memory applications” has been published by Dr Pranab Mandal, Assistant Professor of Physics and his PhD student, Ms K N Malleswari in the journal ‘Current Applied Physics’ having an Impact Factor of 2.480.

Doi: https://doi.org/10.1016/j.cap.2022.04.013

Abstract

Resistive random-access memory (ReRAM) devices are based on the resistance switching (RS) effect. Such RS devices have recently attracted significant attention due to their potential application in realizing the next-generation non-volatile memory (NVM) devices. The present work reports on resistive switching (RS) characteristics of Neodymium (Nd)-doped bismuth ferrite (BFO) layers. The Nd (2–10 at%) doped BFO thin film layers were deposited using a spray pyrolysis method. The structural analysis reveals that a higher Nd doping concentration in BFO leads to significant distortion of the prepared Nd: BFO thin films from rhombohedral to tetragonal characteristics. The morphological analysis shows that all the deposited Nd: BFO thin films have regularly arranged grains. The X-ray photoelectron spectroscopy (XPS) analysis reveals that the prepared Nd: BFO thin films have a higher Fe3+/Fe2+ ratio and fewer oxygen vacancy (VO) defects which enrich the ferroelectric characteristics in Nd: BFO layers. The polarization-electric field (P-E) and RS characteristics of the fabricated Nd: BFO-based RS device were examined. It was observed that the Nd (7 at%) doped BFO RS device shows large remnant polarization (P r) of 0.21 μC/cm2 and stable RS characteristics.

Research in brief

Non-volatile resistive random access memory (RRAM) are future generation random access memory device with potential benefits such as high operational speed (nanoseconds read and write time), non-volatility, high endurance scalability and low power consumption [Namnoscale Research Lett., 15, 90, 2020]. Here in this work, we presented the resistive switching characteristics of a multiferroic material namely Nd-doped BiFeO3 material. The device shows stable resistive switching characteristics.

Practical implementation/social implications

Researchers in this field are focusing to overcome challenges of high operation current, lower resistance ratios, and reliability issues [Namnoscale Research Lett., 15, 90, 2020]. While several prototype RRAMs have been developed by other groups, future memory applications would require overcoming the challenges mentioned above.

Collaboration

The work has been conceptualized by Dr Amiruddin at  Crescent Institute of Science and Technology, Chennai; and Dr Pranab Mandal and Ms Malleswari provided inputs on ferroelectric polarization – electric field (P – E) measurement and drafting.

Research at the Department of Physics is currently exploring the potential applications of NdNiO3. Recently, Professor Ranjit Thapa, and his Ph D student, Mr Deepak S Gavali published the paper, Low-Temperature Spin-Canted Magnetism and Bipolaron Freezing Electrical Transition in Potential Electron Field Emitter NdNiO3 in the journal ACS Applied Electronic Materials, with an Impact Factor of 3.314. This work is done in collaboration with the Department of Physics and Astronomy, National Institute of Technology Rourkela, Rourkela, Odisha, India.

About the research

In this work, NdNiO3 nanoparticles are synthesized by sol-gel auto-combustion techniques, and its primary characterization related to structural and surface morphological analysis is carried out by X-Ray Diffraction (XRD), Fourier Transforms Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray spectroscopy (EDX), and Transmission Electron Microscopy (TEM) techniques. The research is focused on magnetic phase transition below Curie temperature (TN) ∼176 K, and the magnetic susceptibility indicates a weak antiferromagnetic ordering at low temperature. Different ac conduction mechanisms, that is, Correlated Barrier Hopping (CBH), Continuous-Time Random Walk (CTRW) conduction model, and Non-overlapping Small Polaron Tunneling (NSPT), are introduced to interpret its electrical transport behavior near, above, and below TMI ∼178 K. Using first principles and Density of States (DOS) calculation, the researchers have characterized the electronic and magnetic ground state of NdNiO3 at room temperature. It exposed the overlapping of conduction and valence band at room temperature, and the degree of hybridization between Ni 3d and O 2p is very high compared to Nd 5d states. The work function is also calculated for a few-layer NdNiO3 to estimate the field enhancement factor (β), which plays a crucial role in the practical application of a field emitter.

Practical implications

The additional novelty of the present work is to explore the potential application of NdNiO3 as an efficient field emitter and controlled electron/X-ray sources in a flat panel display, microwave vacuum electronic devices, electron microscopy/ lithography, and so forth. To eject conducting electrons from the metal/semiconducting surface by a quantum mechanical tunneling process, sufficient energy is required in terms of the applied electric field (∼106 to 107 V/cm) to overcome the potential barrier at the vacuum−metal interface. The potential difference between the Fermi level (Ef ) of the metal surface to vacuum is known as the work function (Φ). It depends on material characteristics and plays an essential role in field enhancement capability. The primary requirement for efficient field emitters is high aspect ratios (i.e., field enhancement factor), inferior turn-in field, low work, function, etc. Researchers have examined various classes of materials for efficient field emitter electrodes, such as (i) carbonaceous materials like graphene and carbon nanotube, (ii) various 1D and 2D metal oxide and transition metal dichalcogenides like ZnO, MnO2, In2O3, WS2, WSe2, MoS2, PdSe2, etc., (iii) inorganic semiconductors like SiC and Si, and (iv) wide band gap semiconducting compounds GaN, AIN, and so on. The field emission properties of rare earth nickelates (RNiO3; R = La, Gd, Nd, Sm, etc.) with an exciting room temperature metallic nature have not been examined.

The Department of Physics is glad to announce that Dr Soumyajyoti Biswas, Assistant Professor, has published a paper titled ” Near universal values of social inequality indices in self-organized critical models” in the journal Physica A: Statistical Mechanics and its Applications having an impact factor of 3.263. This research was done in collaboration with Prof S S Manna of S N Bose National Center for Basic Sciences and Prof B K Chakrabarti of Saha Institute of Nuclear Physics.

It is well known that wealth invariably accumulates only in a few hands while a majority of the world continues to remain poor. In economics, it is quantified in Pareto’s 80-20 law (20% of people possess 80% of wealth) or ‘The Law of the Vital Few’. This research reveals that the implication of this law goes far beyond the socio-economic systems. It is also a crucial indicator of the onset of critical phenomena in a wide class of physical systems.

It has been observed that in the dynamics of disordered systems, such as fracture and breakdown of solids, slowly increasing the external force produces acoustic emissions (crackling noise), the sizes of which follow Pareto-like behaviour (most noises are weak, only a few are strong that results in the breakdown). Quantifications of these “inequalities” in these physical systems reveal some universal characteristics in a wide class of models, known as self-organized critical systems.

The main implication of this observation lies in predicting catastrophic breakdown in disordered systems. Applications of these inequality measures, which are traditionally in the domain of social sciences, have proved to be immensely useful in identifying the approaching breakdown points in the models of disordered systems. Given that the methods are applicable to a wide variety of models, the 80-20 law has the potential for a wide range of applications. Dr Biswas and his PhD student Diksha are currently working with a team in Spain on experimental data and studying these inequalities in real systems.

The research at the Department of Physics is currently focusing on developing new theoretical frameworks to revamp the fundamental concepts that describe the origin of the universe. Assistant Professor Dr Amit Chakraborty has published a paper titled Revisiting Jet Clustering Algorithms for New Higgs Boson Searches in the Hadronic Final States in the European Physical Journal C, with an Impact Factor of 4.59.

Abstract

Displaced signatures originating from the pair production of a supersymmetric particle, called sneutrino, at the Large Hadron Collider (LHC) are studied. The theoretical model considered in this work is the Next-to-Minimal Supersymmetric Standard Model supplemented with right-handed neutrinos triggering a Type-I seesaw mechanism. The research has shown how such signatures can be established through a heavy Higgs portal when the sneutrinos are decaying to charged leptons and charginos giving rise to further leptons or hadrons. The research also illustrated how the Yukawa parameters of neutrinos can be extracted by measuring the lifetime of the sneutrino from the displaced vertices, thereby characterising the dynamics of the underlying mechanism of neutrino mass generation.

Explanation of the research

The Standard Model of Particle Physics is currently the remarkably successful theory to describe the basic building blocks of the universe and their interactions with the three fundamental forces of nature. Despite its success at explaining the universe, the Standard Model does have several limitations. For example, how neutrinos get their mass, why the mass spectrum of the different elements of SM fermions, namely quarks and leptons, are so hierarchical, why the Higgs boson mass is so low, etc. The primary research is to understand these issues and then propose theoretical models which circumvent these shortcomings of SM and provide signatures that can be tested in the ongoing or future proposed experiments.

For this research project, Dr Amit Chakraborty have collaborated with Particle Physics Department, STFC Rutherford Appleton Laboratory, UK and School of Physics and Astronomy, University of Southampton, UK. His broad research interest is to perform theoretical studies of physics beyond the Standard Model (BSM) in particular, collider search strategies and prospects of different BSM models at the Large Hadron Collider (LHC) and future proposed collider experiments. He aims to build new theoretical models, develop new techniques/tools, and devise new search strategies to improve our knowledge of the standard model as well as BSM physics processes.

Dr Amit Chakraborty’s future research topics include Higgs Boson Physics and Beyond Standard Model Physics Phenomenology, Dark Matter at the Colliders, Interpretable Machine Learning techniques in BSM Physics, and Ultra-light particles and Physics Beyond the Colliders.

Assistant professors Dr Sabyasachi Mukhopadhyay and Dr Imran Pancha from the Department of Physics and the Department of Biological Sciences, respectively, along with Ms Ashwini Nawade, a PhD student of the Department of Physics, have developed a method to integrate plant proteins in the solid-state electronic circuits and utilize the biological functionality to produce a thin film, cost-effective photodetector. Their paper entitled Electron Transport across Phycobiliproteins Films and its’ Optoelectronic Properties has been published in the ECS Journal of Solid State Science and Technology with an Impact Factor of 2.07. It is an interdisciplinary research project between the Department of Biotechnology and Physics.

Explanation of the research

Biomolecules such as proteins, peptides being the most crucial life-forms, have an intimate relationship with various life activities for biological functions. The contemporary work with biomolecules mainly focuses on its evolving potential associated with nanoscale electronics where proteins and peptides are integrated as sensing materials. The researchers explored the optoelectronics functionality of combined proteins known as phycobiliproteins. They investigated electron transport behavior across the phycobiliproteins films under dark and white light illumination. The research affirms that the photochemical activity of the protein is more stable in a solid-state/ thin-film with tightly bonded water molecules than its presence in a buffer solution. Furthermore, the studies demonstrate that phycobiliproteins films modulate their electrical conductivity within their different conformation states. Researchers speculate that the electrical conductance variation could originate from the chemical alteration of cysteine-conjugated bilin chromophores to protein and the electrostatic environment around the chromophores.

The research explores the photochemical properties and electrical transport efficiency of phycobiliproteins (PBPs) films. In addition, it investigates the optoelectronics functionality of PBPs films by studying electron transport behavior across the protein films under a dark state and white light illumination. The researchers proposed to develop a photodetector with the protein film in the future.