School Of Basic And Applied Sciences

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Author: search.filters.author.Kumar, AHas files: Yes

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    Strain tunable Schottky barriers and tunneling characteristics of borophene/MX2 van der Waals heterostructures
    (Elsevier, 2020) Katoch, N; Kumar, A; Sharma, R; Ahluwalia, P.K; Kumar, J.
    Based on first-principle calculations, we report the strain induced changes in electronic properties and their influence on current-voltage (I?V) characteristics of the borophene (?12)/MX2 (M = Mo, W and X = S, Se) vdW heterostructures. The results reveal that the intrinsic electronic nature of borophene and MX2 is retained because of weak van der Waals interactions. However, p-type Schottky contacts are formed at the interface of the heterostructures. Application of the in-plane tensile and compression strains is effective in tuning the Schottky contacts and controlling the SBHs. Also, at the vertical pressure values of 5.46 and 5.25 GPa for ?12/MoS2 and ?12/WS2 respectively, Schottky contact changes from p-type to n-type. The I?V characteristics exhibit an ohmic behavior at low bias ±0.1 v and noticeable NDR on changing positive (negative) biases. Such strain tunable Schottky barriers may be influential in ?12/MX2 based high-performance nano- and optoelectronic devices. - 2020 Elsevier B.V.
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    Ion transport, dielectric, and electrochemical properties of sodium ion-conducting polymer nanocomposite: application in EDLC
    (Springer, 2020) Kumar, A; Madaan, M; Arya, A; Tanwar, S; Sharma, A.L.
    The present paper reports the investigation of structural, electrical, dielectric, and transport properties of the polyethylene oxide (PEO)-based polymer nanocomposite (PNC), with sodium hexafluorophosphate (NaPF6) salt and barium titanate (BaTiO3) as nanofillers. The PNC has been prepared via standard solution casting technique. The structural investigation has been investigated by X-ray diffraction and evidence the enhancement in amorphous content. The morphology has been examined by Field emission scanning electron microscopy technique and confirms the composite formation. The presence of polymer-ion and ion-ion interaction has been confirmed by the Fourier transform infrared spectra (FTIR) and evidences the PNC formation. The impedance spectroscopy has been performed to evaluate the ionic conductivity in the temperature range 40–100 °C.The increase of conductivity is obtained with the addition of nanofiller and temperature-dependent conductivity follows Arrhenius behavior. The PNC film having the highest conductivity exhibits low activation energy and indicates the fast ion migration. The ion transference number is close to unity and the voltage stability window is within the desirable limit. The complex permittivity and complex conductivity have been obtained and the plot has been fitted in the whole frequency window. The fitted plot is in perfect agreement with experimental data. The PNC having the highest conductivity has high dielectric strength and low relaxation time. It confirms the nanofiller role in enhancing ion migration. The ion transport parameters (n, ?, D) are also in correlation with impedance and dielectric analysis. The optimized PNC films have been used to prepare the Electric double-layer capacitors (EDLC) and it demonstrates the improved performance which may be attributed to the effective role played by nanofiller in boosting ion dynamics. - 2020, Springer Science+Business Media, LLC, part of Springer Nature.
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    Novel phosphorus-based 2D allotropes with ultra-high mobility
    (Institute of Physics Publishing, 2020) Kaur, S; Kumar, A; Srivastava, S; Tankeshwar, K; Pandey, R.
    Electronic structure calculations based on density functional theory were performed to investigate structural, mechanical, and electronic properties of phosphorene-based large honeycomb dumbbell (LHD) hybrid structures and a new phosphorene allotrope, referred to as ??-P. The LHD hybrids (i.e., X6P4; X being C or Si or Ge or Sn) and ??-P have significantly higher bandgaps than the corresponding pristine LHD structures, except the case of C6P4, which is metallic. ??-P is found to be a highly flexible p-type material which shows strain-engineered photocatalytic activity in a highly alkaline medium. The carrier mobility of the considered systems is as high as 105 cm2 V-1 s-1 (specifically the electron mobility of LHD structures). The calculated STM images display the surface morphologies of the LHD hybrids and ??-P. The predicted phosphorus-based 2D structures with novel electronic properties may be candidate materials for nanoscale devices. - 2020 IOP Publishing Ltd.
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    Existence of mild solutions for impulsive neutral Hilfer fractional evolution equations
    (Springer, 2020) Bedi, P; Kumar, A; Abdeljawad, T; Khan, A.
    In this paper, we investigate the existence of mild solutions for neutral Hilfer fractional evolution equations with noninstantaneous impulsive conditions in a Banach space. We obtain the existence results by applying the theory of resolvent operator functions, Hausdorff measure of noncompactness, and Sadovskii's fixed point theorem. We also present an example to show the validity of obtained results. 2020, The Author(s).
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    Electronic structure and carrier mobilities of twisted graphene helix
    (Elsevier, 2020) Thakur, R; Ahluwalia, P.K; Kumar, A; Mohan, B; Sharma, R.
    Density functional theory based calculations have been carried out to investigate the effect of twisting on electronic band structures and carrier mobilities of three prototypes of armchair graphene nanoribbons (AGNRs) within the fixed boundary conditions. It is found that twisting causes a modification in the bandgap values and the overall shape of band structures. The values of longitudinal acoustic deformation potential (DP) are found to be higher than the torsional acoustic DP values. The torsional strain is also found to have a profound effect on effective mass and mobilities of given AGNRs. The hole mobility of hydrogen passivated N = 8 AGNRs is found to be comparable with the carrier mobility of intrinsic graphene. The electron mobility of N = 8 AGNRs can be further increased with fluorine passivation. The width, passivation, and extent of twisting together determine n-type or p-type behavior of AGNRs. Fluorine passivated AGNRs are predicted to be potential candidates for mechanical and high-frequency switching. Our results suggest that twisting of AGNRs can be an effective mean for tuning their band structure and carrier mobility for applications in high-speed switching devices. 2020 Elsevier B.V.