Department Of Physics

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Browsing Department Of Physics by Author "Ahluwalia, P.K."

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    Electronic and optical properties of boron-based hybrid monolayers
    (IOP Publishing Ltd, 2021-06-24T00:00:00) Katoch, Neha; Kumar, Ashok; Kumar, Jagdish; Ahluwalia, P.K.; Pandey, Ravindra
    Anisotropic 2D Dirac cone materials are important for the fabrication of nanodevices having direction-dependent characteristics since the anisotropic Dirac cones lead to different values of Fermi velocities yielding variable carrier concentrations. In this work, the feasibility of the B-based hybrid monolayers BX (X = As, Sb, and Bi), as anisotropic Dirac cone materials is investigated. Calculations based on density functional theory and molecular dynamics method find the stability of these monolayers exhibiting unique electronic properties. For example, the BAs monolayer possesses a robust self-doping feature, whereas the BSb monolayer carries the intrinsic charge carrier concentration of the order of 1012 cm?2 which is comparable to that of graphene. Moreover, the direction-dependent optical response is predicted in these B-based monolayers; a high IR response in the x-direction is accompanied with that in the visible region along the y-direction. The results are, therefore, expected to help in realizing the B-based devices for nanoscale applications. � 2021 IOP Publishing Ltd Printed in the UK
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    Optoelectronic and photocatalytic properties of stable pentagonal B2S and B2Se monolayers
    (Elsevier B.V., 2022-06-01T00:00:00) Katoch, Neha; Kumar, Jagdish; Kumar, Ashok; Ahluwalia, P.K.; Pandey, Ravindra
    Boron-based 2D monolayers have attracted tremendous interest due to their unique physical and chemical properties. In this paper, we report novel pentagonal monolayers, B2S and B2Se, which are predicted to be energetically, dynamically, and thermally stable based on density functional theory. At the HSE06 level of theory, they exhibit a moderate indirect bandgap of (e.g., 1.82 eV for Penta-B2S and 1.94 eV for Penta-B2Se). Strain-induced indirect-to-direct bandgap transition, high hole mobility (~103 Cm2V-1S-1) and strong optical absorption (? ~105 Cm-1) in the visible region are observed for these monolayers. Moreover, the electronic band structures and optical spectra are tunable by mechanical strains suggesting their visible light-harvesting capabilities for optoelectronic applications. In this way, the pentagonal family of 2D materials is now expanded to include boron-containing photocatalytic materials for water splitting applications. � 2022
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    Stability and electronic properties of bilayer graphene spirals
    (Elsevier B.V., 2021-01-19T00:00:00) Thakur, Rajesh; Ahluwalia, P.K.; Kumar, Ashok; Sharma, Raman
    Spiral topology offers many potential applications to next-generation nanoelectronic devices. The ab-initio simulations are used to investigate the stability and electronic properties of the hexagonal and triangular double-layer spiral (DLS). A room temperature molecular dynamics (MD) simulation reveals that the AA stacking of triangular DLS (t-DLS) is thermodynamically stable, however, the AA stacking of hexagonal DLS (h-DLS)is found to get distorted. When h-DLS and t-DLS are subjected to tensile strain the h-DLS behaved elastically, however, the t-DLS is extremely brittle. Both h-DLS and t-DLS are observed to be metallic in an equilibrium state. On applying an electric field, the h-DLS remains metallic, whereas, the t-DLS becomes a semiconductor. The bandgap of t-DLS is observed to open up even for a small magnitude of electric field. Furthermore, we also found that the triangular-shaped bilayer spiral topology gives rise to an intrinsic Rashba splitting. Our study opens up new and innovative ideas for investigating the spiral-shaped nano-structures. � 2021 Elsevier B.V.
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    Stability and electronic structure of tricycle-type allotropes of pnictogen monolayers
    (American Institute of Physics, 2019) Jamdagni, P; Thakur, A; Kumar ,Ashok; Ahluwalia, P.K.
    We report stability and electronic structure of tricycle-type allotrope of pnictogen monolayers within state-of-the-art density functional theory (DFT) calculations. The considered monolayer structure of two-dimensional (2D) As and Sb are found to be energetically more stable than the previously reported puckered and buckled structures, however, 2D Bi prefer zigzag-type high-buckled structure. Electronic band structure calculations suggest the considered monolayers structure to be narrow direct bandgap semiconductors with bandgap ranging 0.2-0.6 eV along with Dirac-cone features at band edges. Spin-orbit coupling (SOC) further reduce the bandgap by shifting the band edges towards Fermi level. We believe that our theoretical study will add more 2D materials with Dirac-cone features in the fascinating class of family and may guide the experimentalists to realize them for various nanoelectronic applications. © 2019 Author(s).
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    Stability, electronic and optical properties of in-plane WSe2 heterophase nano-ribbons
    (American Institute of Physics, 2019) Bharti, A; Katoch, N; Kumar, Ashok; Sharma, R; Ahluwalia, P.K.
    We present first principle investigations on in-plane phase engineered nanoribbons with two different widths. 2H and 1T' phases of WSe2 are joined along x-direction, which forms an armchair type interface. The low values of formation energy shows that these structure are energetically stable. The study of electronic structure reveals that they are metallic and the electronic conductivity varies significantly with ribbon length. The ribbons show anisotropic dielectric response compared to constituent monolayers. Optical properties alter considerably for these hetero-systems showing potential for tunable opto-electronic applications. © 2019 Author(s).
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    Twisted helical armchair graphene nanoribbons: mechanical and electronic properties
    (Springer Science and Business Media Deutschland GmbH, 2021-05-08T00:00:00) Thakur, Rajesh; Ahluwalia, P.K.; Kumar, Ashok; Sharma, Munish; Sharma, Raman
    Abstract: The Hydrogen and Fluorine planar armchairs graphene nanoribbons (H & F AGNRs), subjected to twist deformation within fixed periodic boundary conditions. H-AGNRs is highly elastic in nature, though passivation with Fluorine does induce the plasticity when twisted beyond threshold torsional strain. This plasticity attributes to the wider bond length distribution suggests distortion of benzo-rings. The bandgap response to the effective strain of narrow GNRs N= 6 , 7 , and 8 get arranged as (i) monotonously increasing for q= 0 , 2 and (ii) decreasing for q= 1 ; here, q= mod(N, 3) in effective strain space (?2?2). The effective strain space is found to be more appropriate for gauging the response of torsional strain. This trend has also been observed for Fluorine passivated AGNRs; however, because of higher sensitive response to torsional strain, the bandgap of N= 7 F-AGNRs drops from Eg? 0.95 eV to Eg? 0.05 eV at extreme torsional strain forming Dirac cone at � K allows dissipationless transport to charge carriers of high kinetic energy at low bias. Graphic abstract: [Figure not available: see fulltext.] � 2021, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.