Sayani Majumdar

Prof. Dr. Sayani Majumdar

VTT Technical Research Centre of Finland, Espoo, Finland

Research Focus & Metrics

Academic Career Length

22Years (2005-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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3 January 2019 in Advanced Electronic Materials
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Journal Article
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SMSayani Majumdar
Sayani Majumdar
HTHongwei Tan
Hongwei Tan
QQQi Hang Qin
Qi Hang Qin
SDSebastiaan van Dijken
Sebastiaan van Dijken
Energy efficiency, parallel information processing, and unsupervised learning make the human brain a model computing system for unstructured data handling. Different types of oxide memristors can emulate synaptic functions in artificial neuromorphic circuits. However, their cycle‐to‐cycle variability or strict epitaxy requirements remain a challenge for applications in large‐scale neural networks. Here, solution‐processable ferroelectric tunnel junctions (FTJs) with P(VDF‐TrFE) copolymer barriers are reported showing analog memristive behavior with a broad range of accessible conductance states and low energy dissipation of 100 fJ for the onset of depression and 1 pJ for the onset of potentiation by resetting small tunneling currents on nanosecond timescales. Key synaptic functions like programmable synaptic weight, long‐ and short‐term potentiation and depression, paired‐pulse facilitation and depression, and Hebbian and anti‐Hebbian learning through spike shape and timing‐dependent plasticity are demonstrated. In combination with good switching endurance and reproducibility, these results offer a promising outlook on the use of organic FTJ memristors as building blocks in artificial neural networks.

18 September 2006 in Applied Physics Letters
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SMSayani Majumdar
Sayani Majumdar
RLR. Laiho
R. Laiho
PLP. Laukkanen
P. Laukkanen
IVI. J. Väyrynen
I. J. Väyrynen
HMHimadri S. Majumdar
Himadri S. Majumdar
RÖR. Österbacka
R. Österbacka
The authors report on fabrication and characterization of a polymeric spin valve with the conjugated polymer regioregular (poly 3-hexylthiophene) (RRP3HT) as the spacer layer. The device structure is La0.67Sr0.33MnO3 (LSMO)/polymer/Co, with half-metallic, spin-polarized LSMO acting as the spin-injecting electrode. The spin valve shows behavior similar to a magnetic tunnel junction though the nonmagnetic spacer layer (∼100nm) is much thicker than the tunneling limit. They attribute this behavior to the formation of a thin spin-selective tunneling interface between LSMO and RRP3HT caused by RRP3HT, chemically attaching to LSMO as observed by x-ray photoelectron spectroscopy measurement. This gives rise to ∼80% magnetoresistance (MR) at 5K and ∼1.5% MR at room temperature. They found that by introducing monolayer of different organic insulators between LSMO and RRP3HT the spin-selective interface is destroyed and the spin injection is reduced. Their results show that organic materials are promising candidates for spintronic applications.

23 December 2013 in Journal of Physics D: Applied Physics
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SMSayani Majumdar
Sayani Majumdar
SDSebastiaan van Dijken
Sebastiaan van Dijken
Materials engineering on the nanoscale by precise control of growth parameters can lead to many unusual and fascinating physical properties. The development of pulsed laser deposition (PLD) 25 years ago has enabled atomistic control of thin films and interfaces and as such it has contributed significantly to advances in fundamental material science. One application area is the research field of spintronics, which requires optimized nanomaterials for the generation and transport of spin-polarized carriers. The mixed-valence manganite La1−xSrxMnO3 (LSMO) is an interesting material for spintronics due to its intrinsic magnetoresistance properties, electric-field tunable metal–insulator transitions, and half-metallic band structure. Studies on LSMO thin-film growth by PLD show that the deposition temperature, oxygen pressure, laser fluence, strain due to substrate–film lattice mismatch and post-deposition annealing conditions significantly influence the magnetic and electrical transport properties of LSMO. For spintronic structures, robust ferromagnetic exchange interactions and metallic conductivity are desirable properties. In this paper, we review the physics of LSMO thin films and the important role that PLD played in advancing the field of LSMO-based spintronics. Some specific application areas including magnetic tunnel junctions, multiferroic tunnel junctions and organic spintronic devices are highlighted, and the advantages, drawbacks and opportunities of PLD-grown LSMO for next-generation spintronic devices are discussed.

1 June 2016 in Advanced Materials
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Journal Article
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QQQi Hang Qin
Qi Hang Qin
LÄLaura Äkäslompolo
Laura Äkäslompolo
NTNoora Tuomisto
Noora Tuomisto
LYLide Yao
Lide Yao
SMSayani Majumdar
Sayani Majumdar
SDSebastiaan van Dijken
Sebastiaan van Dijken

1 July 2022 in Advanced Materials
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Journal Article
Open access
Gianluca MilanoGianluca Milano
Gianluca Milano
MAMasakazu Aono
Masakazu Aono
Luca BoarinoLuca Boarino
Luca Boarino
UCUmberto Celano
Umberto Celano
THTsuyoshi Hasegawa
Tsuyoshi Hasegawa
Ilia ValovIlia Valov
Ilia Valov
Quantum effects in novel functional materials and new device concepts represent a potential breakthrough for the development of new information processing technologies based on quantum phenomena. Among the emerging technologies, memristive elements that exhibit resistive switching, which relies on the electrochemical formation/rupture of conductive nanofilaments, exhibit quantum conductance effects at room temperature. Despite the underlying resistive switching mechanism having been exploited for the realization of next‐generation memories and neuromorphic computing architectures, the potentialities of quantum effects in memristive devices are still rather unexplored. Here, a comprehensive review on memristive quantum devices, where quantum conductance effects can be observed by coupling ionics with electronics, is presented. Fundamental electrochemical and physicochemical phenomena underlying device functionalities are introduced, together with fundamentals of electronic ballistic conduction transport in nanofilaments. Quantum conductance effects including quantum mode splitting, stability, and random telegraph noise are analyzed, reporting experimental techniques and challenges of nanoscale metrology for the characterization of memristive phenomena. Finally, potential applications and future perspectives are envisioned, discussing how memristive devices with controllable atomic‐sized conductive filaments can represent not only suitable platforms for the investigation of quantum phenomena but also promising building blocks for the realization of integrated quantum systems working in air at room temperature.

19 February 2014 in Advanced Materials
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Journal Article
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LYLide Yao
Lide Yao
SMSayani Majumdar
Sayani Majumdar
LÄLaura Äkäslompolo
Laura Äkäslompolo
SISampo Inkinen
Sampo Inkinen
QQQi Hang Qin
Qi Hang Qin
SDSebastiaan van Dijken
Sebastiaan van Dijken