Browsing by Author "Sharma, Munish"
Now showing 1 - 10 of 10
Results Per Page
Sort Options
Item Alloyed monolayers of Cu, Ag, Au and Pt in hexagonal phase: A comprehensive first principles study(Elsevier Ltd, 2018) Kapoor, Pooja; Kumar, Arun; Sharma, Munish; Kumar, Jagdish; Kumar, Ashok; Ahluwalia, P. K.We present density functional theory (DFT) based comprehensive study of two-dimensional (2D) alloyed monolayers of noble metals (AgCu, AgPt, AgAu, AuCu, AuPt and CuPt) in hexagonal phase within numerical atomic orbitals and plane wave basis sets methods. The monolayers considered exhibit positive phonon frequencies suggesting them to be dynamically stable. The Pt containing alloyed monolayers have superior structural stability (binding energy and tensile strength) and exhibit metallic and ferromagnetic character amongst all the alloyed monolayers. Interestingly, alloying of Au monolayer with Cu and Ag show semiconducting behavior whereas alloyed AgCu monolayer posseses Dirac-cone like features at high symmetry points. These distinct features in electronic structures of alloyed 2D monolayers have been captured in STM like set up. An anisotropic behavior has been observed in dielectric spectra for all the considered structures. Tunneling characteristics show NDR region for Pt containing alloyed monolayers. The considered alloyed monolayers may potentially be useful as a building blocks for the applications in nano- and opto-electronics. ? 2017 Elsevier B.V.Item Armchair and zigzag nanoribbons of gold and silver: A DFT study(American Institute of Physics Inc., 2018) Kapoor, Pooja; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.This paper presents the results from a DFT-based computational study of structural and electronic properties of zigzag and armchair edge shaped nanoribbons of gold and silver in hexagonal phase. The cohesive energy of the considered nanoribbons are found to be more than the corresponding 2D counterpart, thereby, suggesting Au and Ag nanoribbons to be more stable in 1D as compared to 2D. All nanoribbons are found to be metallic with a modulation in quantum ballistic conductance with length and edge type of the nanoribbon. Au nanoribbons are found to have higher conductance than Ag nanoribbon. There is increase in conductance with increase in length of nanoribbon. ? 2018 Author(s).Item 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.Item Electronic properties of ZnPSe3-MoS2 Van der Waals heterostructure(American Institute of Physics Inc., 2018) Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.We present a comparative study of electronic properties of ZnPSe3-MoS2 heterostructure using GGA-PBE functional and DFT-D2 method within the framework of density functional theory (DFT). Electronic band structure for the considered heterostructure shows a direct band gap semiconducting character. A decrease in band gap is observed with the heterostructuring as compared to their constituent pristine monolayers. The alignment of valance band maxima and conduction band minima on different layers in heterostructure indicate the physical separation of charge carriers. A work function of 5.31 eV has been calculated for ZnPSe3-MoS2 heterostructure. These results provide a physical basis for the potential applications of these ZnPSe3-MoS2 heterostructure in optoelectronic devices. ? 2018 Author(s).Item First principles study of electronic and thermoelectric performance of Li intercalated MoSe 2 nanotubes(American Institute of Physics Inc., 2017) Sharma, Munish; Kumar, Ashok; Pandey, Rabindra; Ahluwalia, P. K.We present a comparative study of pristine and Li intercalated MoSe 2 nanotube of armchair (6, 6) and zigzag (10, 0) chirality within the framework of density functional theory (DFT). Pristine nanotube is found to have band gap which vanishes upon Li intercalation. Additionally, Li intercalation results in reduction of room temperature ZT e for armchair MoSe 2 nanotube and enhancement in ZT e for intercalated zigzag MoSe 2 nanotube as compared to respective pristine nanotubes. Our results suggest that Li intercalation leads to a relatively high Seeback coefficient which may enhance the thermoelectric performance of zigzag MoSe 2 nanotube.Item Interactions of Gas Molecules with Monolayer MoSe 2 : A First Principle Study(AIP Publishing, 2016) Sharma, Munish; Jamdagni, Pooja; Kumar, Ashok; Ahluwalia, P. K.We present a first principle study of interaction of toxic gas molecules (NO, NO2 and SO2) with MoSe2. The predicted order of sensitivity of gas molecule is NO2 > SO2 > NO. strongly influence the electronic behaviour of MoSe2 by inducing in the vicinity of Fermi energy. NO and SO2 is found to induce p-type effect while to metallic transitions occur on NO2 Our findings may guide the experimentalist for sensor based on MoSe2Item Optical fingerprints and electron transport properties of DNA bases adsorbed on monolayer MoS 2(Royal Society of Chemistry, 2016) Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.Electronic, optical and transport properties of DNA nucleobase adsorbed on monolayer MoS2 has been investigated using density functional theory. A significant polarization in MoS2 has been observed upon DNA nucleobase adsorption. The nucleobase origin of the modulation in the electronic properties is clearly captured in the simulated STM measurements. The electronic transport through conjugate systems allows the clear distinction of nucleobases from one another. The modulation in electron energy loss spectra and transport properties of pristine MoS2 has been observed on nucleobase adsorption which could serve as a fingerprint for realization of next generation DNA sequencing devices. We believe that these results also bring out the possibility of fabrication of MoS2 based biosensors for selective detection of DNA bases in real long-chain DNA molecules.Item Stability, structural and electronic properties of benzene molecule adsorbed on free standing Au layer(American Institute of Physics Inc., 2016) Katoch, Neha; Kapoor, Pooja; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.We report stability and electronic properties of benzene molecule adsorbed on the Au atomic layer within the framework of density function theory (DFT). Horizontal configuration of benzene on the top site of Au monolayer prefers energetically over other studied configurations. On the adsorption of benzene, the ballistic conductance of Au monolayer is found to decrease from 4G0 to 2G0 suggesting its applications for the fabrications of organic sensor devices based on the Au atomic layers. ? 2016 Author(s).Item Structural, electronic and magnetic properties of Au-based monolayer derivatives in honeycomb structure(American Institute of Physics Inc., 2016) Kapoor, Pooja; Sharma, Munish; Kumar, Ashok; Ahluwalia, P. K.We present electronic properties of atomic layer of Au, Au2-N, Au2-O and Au2-F in graphene-like structure within the framework of density functional theory (DFT). The lattice constant of derived monolayers are found to be higher than the pristine Au monolayer. Au monolayer is metallic in nature with quantum ballistic conductance calculated as 4G0. Similarly, Au2-N and Au2-F monolayers show 4G0 and 2G0 quantum conductance respectively while semiconducting nature with calculated band gap of 0.28 eV has been observed for Au2-O monolayer. Most interestingly, half metalicity has been predicted for Au2-N and Au2-F monolayers. Our findings may have importance for the application of these monolayers in nanoelectronic and spintronics. ? 2016 Author(s).Item 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, RamanAbstract: 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.