Browsing by Author "Thakur, Anil"

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    Electronic properties and STM images of vacancy clusters and chains in functionalized silicene and germanene
    (Elsevier B.V., 2017) Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.
    Electronic properties and STM topographical images of X (=F, H, O) functionalized silicene and germanene have been investigated by introducing various kind of vacancy clusters and chain patterns in monolayers within density functional theory (DFT) framework. The relative ease of formation of vacancy clusters and chain patterns is found to be energetically most favorable in hydrogenated silicene and germanene. F- and H-functionalized silicene and germanene are direct bandgap semiconducting with bandgap ranging between 0.1?1.9?eV, while O-functionalized monolayers are metallic in nature. By introducing various vacancy clusters and chain patterns in both silicene and germanene, the electronic and magnetic properties get modified in significant manner e.g. F- and H-functionalized silicene and germanene with hexagonal and rectangle vacancy clusters are non-magnetic semiconductors with modified bandgap values while pentagonal and triangle vacancy clusters induce metallicity and magnetic character in monolayers; hexagonal vacancy chain patterns induce direct-to-indirect gap transition while zigzag vacancy chain patterns retain direct bandgap nature of monolayers. Calculated STM topographical images show distinctly different characteristics for various type of vacancy clusters and chain patterns which may be used as electronic fingerprints to identify various vacancy patterns in silicene and germanene created during the process of functionalization. ? 2016 Elsevier B.V.
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    Energetics and Electronic Properties of Pt Wires of Different Topologies on Monolayer MoSe 2
    (AIP Publishing, 2016) Jamdagni, Pooja; Kumar, Ashok; Thakur, Anil; Pandey, Ravindra; Ahluwalia, P. K.
    The energetics and electronic properties of different of Pt wires including linear, zigzag and ladder structures on MoSe2 have been investigated in the framework of The predicted order of stability of Pt wire on MoSe2 is found to be: linear > ladder > zigzag. Pt wires induce states near the of MoSe2 that results into metallic characteristics of Pt-wire/MoSe2 assembled system. signifies most of the contribution from Pt atoms near the Fermi energy of assembled wire/MoSe2 system. These findings are expected to be important for the of based on MoSe2 layers for flexible nanoelectronics.
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    Tunnelling Characteristics of Stone-Wales Defects in Monolayers of Sn and Group- V Elements
    (Institute of Physics (IOP), 2017) Jamdagni, Pooja; Kumar, Ashok; Thakur, Anil; Pandey, Ravindra; Ahluwalia, P. K.
    Topological defects in ultrathin layers are often formed during synthesis and processing, thereby, strongly influencing the electronic properties of the layered systems. For the monolayers of Sn and group-V elements, we report the results based on density functional theory determining the role of Stone-Wales (SW) defects in modifying their electronic properties. The calculated results find the electronic properties of Sn monolayer to be strongly dependent on the concentration of SW-defects e.g., defective stanene has nearly zero band gap (≈ 0.03 eV) for the defect concentration of 2.2 x 10<sup>13</sup> cm<sup>-2</sup> which opens up to 0.2 eV for the defect concentration of 3.7 x 10<sup>13</sup> cm<sup>-2</sup>. In contrast, SW-defects appear to induce conduction states in the semiconducting monolayers of group-V elements. These conduction states act as channels for electron tunnelling, and the calculated tunnelling characteristics show the highest differential conductance for the negative bias with the asymmetric current-voltage characteristics. On the other hand, the highest differential conductance was found for the positive bias in stanene. Simulated STM topographical images of stanene and group-V monolayers show distinctly different features in terms of their cross-sectional views and distance-height profiles. These distinctive features can serve as fingerprints to identify the topological defects in experiments for the monolayers of group-IV and group-V elements.
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    Two dimensional allotropes of arsenene with a wide range of high and anisotropic carrier mobility
    (Royal Society of Chemistry, 2018) Jamdagni, Pooja; Thakur, Anil; Kumar, Ashok; Ahluwalia, P. K.; Pandey, Ravindra
    Considering the rapid development of experimental techniques for fabricating 2D materials in recent years, various monolayers are expected to be experimentally realized in the near future. Motivated by the recent research activities focused on the honeycomb arsenene monolayers, the stability and carrier mobility of non-honeycomb and porous allotropic arsenene are determined using first principles calculations. In addition to five honeycomb structures of arsenene, a total of eight other structures are considered in this study. An extensive analysis comprising energetics, phonon spectra and mechanical properties confirms that these structures are energetically and dynamically stable. All these structures are semiconductors with a broad range of band gaps varying from ?1 eV to ?2.5 eV. Significantly, these monolayer allotropes possess anisotropic carrier mobilities as high as several hundred cm 2 V -1 s -1 which is comparable with well-known 2D materials such as black phosphorene and monolayer MoS 2 . Combining such broad band gaps and superior carrier mobilities, these monolayer allotropes can be promising candidates for the superior performance of the next generation nanoscale devices. We further explore these monolayer allotropes for photocatalytic water splitting and find that arsenene monolayers have potential for usage in visible light driven photocatalytic water splitting.