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  1. Article ; Online: Atomically thin optomemristive feedback neurons.

    Syed, Ghazi Sarwat / Zhou, Yingqiu / Warner, Jamie / Bhaskaran, Harish

    Nature nanotechnology

    2023  Volume 18, Issue 9, Page(s) 1036–1043

    Abstract: Cognitive functions such as learning in mammalian brains have been attributed to the presence of neuronal circuits with feed-forward and feedback topologies. Such networks have interactions within and between neurons that provide excitory and inhibitory ... ...

    Abstract Cognitive functions such as learning in mammalian brains have been attributed to the presence of neuronal circuits with feed-forward and feedback topologies. Such networks have interactions within and between neurons that provide excitory and inhibitory modulation effects. In neuromorphic computing, neurons that combine and broadcast both excitory and inhibitory signals using one nanoscale device are still an elusive goal. Here we introduce a type-II, two-dimensional heterojunction-based optomemristive neuron, using a stack of MoS
    MeSH term(s) Animals ; Neural Networks, Computer ; Feedback ; Neurons/physiology ; Machine Learning ; Brain ; Mammals
    Language English
    Publishing date 2023-05-04
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2254964-X
    ISSN 1748-3395 ; 1748-3387
    ISSN (online) 1748-3395
    ISSN 1748-3387
    DOI 10.1038/s41565-023-01391-6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Publisher Correction: Atomically thin optomemristive feedback neurons.

    Syed, Ghazi Sarwat / Zhou, Yingqiu / Warner, Jamie / Bhaskaran, Harish

    Nature nanotechnology

    2023  Volume 18, Issue 7, Page(s) 828

    Language English
    Publishing date 2023-06-28
    Publishing country England
    Document type Published Erratum
    ZDB-ID 2254964-X
    ISSN 1748-3395 ; 1748-3387
    ISSN (online) 1748-3395
    ISSN 1748-3387
    DOI 10.1038/s41565-023-01475-3
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Chalcogenide optomemristors for multi-factor neuromorphic computation

    Syed Ghazi Sarwat / Timoleon Moraitis / C. David Wright / Harish Bhaskaran

    Nature Communications, Vol 13, Iss 1, Pp 1-

    2022  Volume 9

    Abstract: Some types of machine learning rely on the interaction between multiple signals, which requires new devices for efficient implementation. Here, Sarwat et al demonstrate a memristor that is both optically and electronically active, enabling computational ... ...

    Abstract Some types of machine learning rely on the interaction between multiple signals, which requires new devices for efficient implementation. Here, Sarwat et al demonstrate a memristor that is both optically and electronically active, enabling computational models such as three factor learning.
    Keywords Science ; Q
    Language English
    Publishing date 2022-04-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Structural Assessment of Interfaces in Projected Phase-Change Memory

    Valeria Bragaglia / Vara Prasad Jonnalagadda / Marilyne Sousa / Syed Ghazi Sarwat / Benedikt Kersting / Abu Sebastian

    Nanomaterials, Vol 12, Iss 1702, p

    2022  Volume 1702

    Abstract: Non-volatile memories based on phase-change materials have gained ground for applications in analog in-memory computing. Nonetheless, non-idealities inherent to the material result in device resistance variations that impair the achievable numerical ... ...

    Abstract Non-volatile memories based on phase-change materials have gained ground for applications in analog in-memory computing. Nonetheless, non-idealities inherent to the material result in device resistance variations that impair the achievable numerical precision. Projected-type phase-change memory devices reduce these non-idealities. In a projected phase-change memory, the phase-change storage mechanism is decoupled from the information retrieval process by using projection of the phase-change material’s phase configuration onto a projection liner. It has been suggested that the interface resistance between the phase-change material and the projection liner is an important parameter that dictates the efficacy of the projection. In this work, we establish a metrology framework to assess and understand the relevant structural properties of the interfaces in thin films contained in projected memory devices. Using X-ray reflectivity, X-ray diffraction and transmission electron microscopy, we investigate the quality of the interfaces and the layers’ properties. Using demonstrator examples of Sb and Sb 2 Te 3 phase-change materials, new deposition routes as well as stack designs are proposed to enhance the phase-change material to a projection-liner interface and the robustness of material stacks in the devices.
    Keywords in-memory computing ; projected phase-change memory ; interface engineering ; confined phase-change material ; sputtering deposition ; X-ray reflectivity ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2022-05-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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  5. Article: Grain Boundaries as Electrical Conduction Channels in Polycrystalline Monolayer WS₂

    Zhou, Yingqiu / Syed Ghazi Sarwat / Gang Seob Jung / Markus J. Buehler / Harish Bhaskaran / Jamie H. Warner

    ACS applied materials & interfaces. 2019 Feb. 28, v. 11, no. 10

    2019  

    Abstract: We show that grain boundaries (GBs) in polycrystalline monolayer WS₂ can act as conduction channels with a lower gate onset potential for field-effect transistors made parallel, compared to devices made in pristine areas and perpendicular to GBs. ... ...

    Abstract We show that grain boundaries (GBs) in polycrystalline monolayer WS₂ can act as conduction channels with a lower gate onset potential for field-effect transistors made parallel, compared to devices made in pristine areas and perpendicular to GBs. Localized doping at the GB causes photoluminescence quenching and a reduced Schottky barrier with the metal electrodes, resulting in higher conductivity at lower applied bias values. Samples are grown by chemical vapor deposition with large domains of ∼100 μm, enabling numerous devices to be made within single domains, across GBs and at many similar sites across the substrate to reveal similar behaviors. We corroborate our electrical measurements with Kelvin probe microscopy, highlighting the nature of the doping-type in the material to change at the grain boundaries. Molecular dynamics simulations of the GB are used to predict the atomic structure of the dislocations and meandering tilt GB behavior on the nanoscale. These results show that GBs can be used to provide conduction pathways that are different to transport across GBs and in pristine area for potential electronic applications.
    Keywords electrical conductivity ; electrodes ; materials science ; microscopy ; molecular dynamics ; photoluminescence ; simulation models ; transistors ; vapors
    Language English
    Dates of publication 2019-0228
    Size p. 10189-10197.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021/acsami.8b21391
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Inhomogeneous Strain Release during Bending of WS₂ on Flexible Substrates

    Tweedie, Martin E. P / Yuewen Sheng / Syed Ghazi Sarwat / Wenshuo Xu / Harish Bhaskaran / Jamie H. Warner

    ACS applied materials & interfaces. 2018 Nov. 01, v. 10, no. 45

    2018  

    Abstract: Two-dimensional (2D) materials hold great promise in flexible electronics, but the weak van der Waals interlayer bonding may pose a problem during bending, where easy interlayer sliding can occur. Furthermore, thin films of rigid materials are often ... ...

    Abstract Two-dimensional (2D) materials hold great promise in flexible electronics, but the weak van der Waals interlayer bonding may pose a problem during bending, where easy interlayer sliding can occur. Furthermore, thin films of rigid materials are often observed to delaminate from soft substrates during straining. Here, we study the influence of substrate strain on some of the heterostructure configurations we expect to find in devices, composed of three common 2D materials: graphene, tungsten disulfide, and boron nitride. We used photoluminescence (PL) spectroscopy to measure changes in the heterostructures with strain applied in situ. All heterostructures were fabricated directly on polymer substrates, using materials synthesized by chemical vapor deposition. We observed an inhomogeneous release of strain in all structures, leading to a nonrecoverable broadening of the PL peak and shift of the bandgap. This suggests the need for preconditioning devices before service to ensure stable behavior. A gradual time-dependent relaxation of strain between strain cycles was characterized using time-dependent measurements—an effect which could lead to drift of device behavior during operation. Furthermore, possible degradation was assessed by performing the strain and relax the cycle up to 200 times, where we found little further change after the initial shifts had stabilized. These results have important ramifications for devices fabricated from these and other 2D materials, as they suggest extra processing steps and considerations that must be taken to achieve consistent and stable properties.
    Keywords boron nitride ; electronics ; graphene ; photoluminescence ; polymers ; spectroscopy ; tungsten ; van der Waals forces ; vapors
    Language English
    Dates of publication 2018-1101
    Size p. 39177-39186.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021/acsami.8b12707
    Database NAL-Catalogue (AGRICOLA)

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  7. Article: Large Dendritic Monolayer MoS2 Grown by Atmospheric Pressure Chemical Vapor Deposition for Electrocatalysis

    Xu, Wenshuo / Sha Li / Si Zhou / Ja Kyung Lee / Shanshan Wang / Syed Ghazi Sarwat / Xiaochen Wang / Harish Bhaskaran / Mauro Pasta / Jamie H. Warner

    ACS applied materials & interfaces. 2018 Feb. 07, v. 10, no. 5

    2018  

    Abstract: The edge sites of MoS₂ are catalytically active for the hydrogen evolution reaction (HER), and growing monolayer structures that are edge-rich is desirable. Here, we show the production of large-area highly branched MoS₂ dendrites on amorphous SiO₂/Si ... ...

    Abstract The edge sites of MoS₂ are catalytically active for the hydrogen evolution reaction (HER), and growing monolayer structures that are edge-rich is desirable. Here, we show the production of large-area highly branched MoS₂ dendrites on amorphous SiO₂/Si substrates using an atmospheric pressure chemical vapor deposition and explore their use in electrocatalysis. By tailoring the substrate construction, the monolayer MoS₂ evolves from triangular to dendritic morphology because of the change of growth conditions. The rough edges endow dendritic MoS₂ with a fractal dimension down to 1.54. The highly crystalline basal plane and the edge of the dendrites are visualized at atomic resolution using an annular dark field scanning transmission electron microscope. The monolayer dendrites exhibit strong photoluminescence, which is indicative of the direct band gap emission, which is preserved after being transferred. Post-transfer sulfur annealing restores the structural defects and decreases the n-type doping in MoS₂ monolayers. The annealed MoS₂ dendrites show good and highly durable HER performance on the glassy carbon with a large exchange current density of 32 μA cmgₑₒ–², demonstrating its viability as an efficient HER catalyst.
    Keywords annealing ; atmospheric pressure ; carbon ; catalysts ; dendrites ; fractal dimensions ; hydrogen production ; materials science ; molybdenum disulfide ; photoluminescence ; sulfur ; transmission electron microscopes ; vapors ; viability
    Language English
    Dates of publication 2018-0207
    Size p. 4630-4639.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1944-8252
    DOI 10.1021/acsami.7b14861
    Database NAL-Catalogue (AGRICOLA)

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