| 1. |
- Naqvi, Syeda Rabab, et al.
(författare)
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Exploring two-dimensional M2NS2 (M = Ti, V) MXenes based gas sensors for air pollutants
- 2020
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Ingår i: Applied Materials Today. - : Elsevier. - 2352-9407. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- Albeit a very recent development, Mxenes have offered numerous potential avenues for researchers from physics, chemistry and materials science. Here in, we have explored S-terminated M2N (M = Ti, V) MXenes, which are one of the lightest and thinnest members of the MXene family, for gas sensing applications. We performed spin-polarized DFT calculations with vdW correction to investigate the sensing propensity of several gases such as CH4, CO, CO2, NH3, NO, NO2, H2S, and SO2 on M2NS2 sheets. The adsorption kinetics, charge transfer, electronic density of states (DOS) and electronic transport behaviors are investigated in relation to M2NS2 Mxene based nanoscale gas sensor. Among all the gases under consideration, NO, and NO2 exhibit superior sensitivity towards 2D nitride MXenes. Charge transfer analysis reveals that the considerable quantity of charge is transferred from NO, and NO2 gas molecules to Ti2NS2 and V2NS2 MXene sheets, respectively. Spin-polarized DOS reveals that pristine non-magnetic nitride Mxenes transform to magnetic systems upon NO and NO2 adsorption. By computing the electronic transport properties in the form of I–V characteristics for adsorbed gases on M2NS2 and comparing it against the pristine Mxene sheets, distinct changes in I–V relationships can be identified which further substantiate the promising role of Mxenes for gas sensing applications.
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| 2. |
- Mahida, H. R., et al.
(författare)
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The influence of edge structure on the optoelectronic properties of Si2BN quantum dot
- 2019
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Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 126:23
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Tidskriftsartikel (refereegranskat)abstract
- In recent work, we have investigated the electronic and optical properties of pristine and functionalized Si2BN quantum dots (QDs) using first-principles calculations. Due to the edge functionalization, Si2BN QDs have binding energies of -0.96 eV and -2.08 eV per hydrogen atom for the adsorption of single and double hydrogen atoms, respectively. These results reveal the stability and the bonding nature of hydrogen at the edges of Si2BN QD. In particular, the charge transfer between hydrogen and other atoms is explicitly increased. The electronic band structure of pristine Si2BN QD shows a metallic behavior with a finite number of electronic states in the density of states at the Fermi level. The frequency-dependent optical properties, such as refractive index, extinction coefficient, absorption coefficient, electron energy loss spectra, and reflectivity, are computed for both the parallel and perpendicular components of electric field polarization. The higher absorption was found in the infrared regime. The present study shows that the functionalization of Si2BN QD by two hydrogen atoms is energetically stable. It offers a promising application of Si2BN QD, which can be used in optical nanodevices such as photodetectors and biomedical imagination.
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| 3. |
- Mallik, Sameer Kumar, et al.
(författare)
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Salt-assisted growth of monolayer MoS2 for high-performance hysteresis-free field-effect transistor
- 2021
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 129:14
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Tidskriftsartikel (refereegranskat)abstract
- Atomically thin layered materials such as MoS2 have future versatile applications in low power electronics. Here, we demonstrate the growth of a salt-assisted large scale, high-quality monolayer MoS2 toward the realization of a high-performance hysteresis-free field-effect transistor (FET). Density functional theory calculations are implemented to monitor the effects of the Schottky barrier and metal-induced gap states between our metal electrodes and MoS2 for achieving high carrier transport. The role of absorbed molecules and oxide traps on the hysteresis are studied in detail. For the first time, a hysteresis-free intrinsic transistor behavior is obtained by an amplitude sweep pulse I-V measurement with varying pulse widths. Under this condition, a significant enhancement of the field-effect mobility up to 30cm(2)V(-1)s(-1) is achieved. Moreover, to correlate these results, a single-pulse time-domain drain current analysis is carried out to unleash the fast and slow transient charge trapping phenomena. Our findings on the hysteresis-free transfer characteristic and high intrinsic field-effect mobility in salt-assisted monolayer MoS2 FETs will be beneficial for future device applications in complex memory, logic, and sensor systems.
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| 4. |
- Singh, Deobrat, et al.
(författare)
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Promising high-temperature thermoelectric response of bismuth oxybromide
- 2020
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Ingår i: Results in Physics. - : Elsevier. - 2211-3797. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the bismuth oxybromide quintuple-layer (QL) was experimentally realized. In the present study, we extensively examine the stability, electronic and thermal transport of bulk bismuth oxybromide (BiOBr) and QL based on first-principles calculations and the semiclassical Boltzmann transport theory. We have found that the bulk and QL BiOBr systems are dynamically and thermally stable with an indirect band gap of 2.86 and 3.08 eV, respectively. The emergence of comparatively flat bands at the top valence band favours the pronounced p-type Seebeck coefficient. Our calculated results demonstrate a high Seebeck coefficient of 1569.82 μV/K and 1580 μV/K for bulk and QL BiOBr materials at high temperatures. At higher temperature, the lattice thermal conductivity values of bulk are 1.32/0.23 for in-plane/out-of-plane, respectively and 1.85 W/mK in QL BiOBr, which are relatively low compared to other layered materials, e.g., MX2 (M = Mo, W, Pt, Zr, and X = S, Se, Te). The figure of merit (ZT) turns out to be as high as 3.52 for bulk BiOBr and 1.5 for QL BiOBr at higher temperatures,suggest them as good candidates for thermoelectric applications.
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| 5. |
- Bhuyan, Prabal Dev, et al.
(författare)
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Metallic one-dimensional heterostructure for gas molecule sensing
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated a new metallic core-shell nanowire (NW) geometry of that could be obtained experimentally, that is silicon (Si) and germanium (Ge) NWs with cores constituted by group-10 elements palladium (Pd) and platinum (Pt). These NWs are optimized with two different diameters of 1.5 angstrom and 2.5 angstrom. The nanowires having diameter of 1.5 angstrom show semi-metallic nature with GGA-PBE calculation and metallic nature while spin orbit interaction (SOC) is included. The quantum conductance of the NWs increases with the diameter of the nanowire. We have investigated current-voltage (IV) characteristics for the considered NWs. It has been found that current values in accordance with applied voltage show strong dependence on the diameter of the NWs. The optical study of the NWs shows that absorption co-efficient peak moves to lower energies; due to quantum confinement effect. Furthermore, we have extensively studied optical response of Pd and Pt based core-shell NWs in O-2 and CO2 environment. Our study on Si and Ge based metallic core/shell NW show a comprehensive picture as possible electron connector in future nano-electronic devices as well as nano gas detector for detecting O-2 gas.
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| 6. |
- Mahida, H. R., et al.
(författare)
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Hydrogenation and oxidation enhances the thermoelectric performance of Si2BN monolayer
- 2021
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 45:8, s. 3892-3900
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we have investigated the structural, electronic, and charge transport properties of pristine, hydrogenated, and oxidized Si2BN monolayers via first-principles calculations based on density functional theory (DFT). Hydrogenation and oxidation of Si2BN monolayer display negative binding energy therefore these structures are energetically favorable. The electronic band structure engineered by the hydrogenation and oxidation of the Si2BN monolayer transformed from metallic to semiconducting nature. Due to the hydrogenation and oxidation of Si2BN, the monolayer also changes from a planar structure to a non-planar structure. The hydrogenated and oxidized structures led to high thermoelectric performance as compared to the pristine Si2BN monolayer. When the Si2BN monolayer is hydrogenated and oxidized, its electronic figure of merit (ZT(e)) significantly enhanced from 0.45 to 0.99. The investigation results suggest a practical approach for improving the performance of thermoelectric properties of the Si2BN monolayer.
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| 7. |
- Mishra, Pushkar, et al.
(författare)
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Metal-functionalized 2D boron sulfide monolayer material enhancing hydrogen storage capacities
- 2020
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 127:18
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we have systematically investigated the structural, electronic, vibrational, and H2 storage properties of a layered 2H boron sulfide (2H-BS) monolayer using spin-polarized density functional theory (DFT). The pristine BS monolayer shows semiconducting behavior with an indirect bandgap of 2.83 eV. Spin-polarized DFT with van der Waals correction suggests that the pristine BS monolayer has weak binding strength with H2 molecules, but the binding energy can be significantly improved by alkali metal functionalization. A system energy study indicates the strong bonding of alkali metals with the BS monolayer. The Bader charge analysis also concludes that a considerable charge is transferred from the metal to the BS monolayer surface, which was further confirmed by the iso-surface charge density profile. All functionalized alkali metals form cations that can bond multiple H2 molecules with sufficient binding energies, which are excellent for H2 storage applications. An ideal range of adsorption energy and practicable desorption temperature promises the ability of the alkali metal functionalized BS monolayer as an efficient material for hydrogen storage.
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| 8. |
- Sahu, Mousam Charan, et al.
(författare)
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Effect of Charge Injection on the Conducting Filament of Valence Change Anatase TiO2 Resistive Random Access Memory Device
- 2021
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 12:7, s. 1876-1884
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Tidskriftsartikel (refereegranskat)abstract
- The recent observation of stable quantized conductance in anatase TiO2 resistive random access memory (ReRAM) devices opens up a new pathway toward the realization of brain-inspired neuromorphic computing devices. Herein, for the first time, ab initio calculations are implemented to understand the resistive switching phenomena in anatase TiO2. Oxygen vacancy configurations with different charge states are studied to gain insight into the ON and OFF states of ReRAM devices. Among the trivacancy configurations, the V-o(+) state is observed to induce highly dispersed defect states within the bandgap forming a charge density channel where the carriers behave as free electrons leading to the formation of a conducting filament (CF). On the contrary, the breakdown of the CF is noticed by the removal of an oxygen vacancy from the trivacancy configuration. In this OFF state, the defect state carriers are found to be highly localized. In addition, we have also investigated the effect of charge injection on the crystal field symmetry of the CF. The reduction of symmetry due to the trivacancy configuration lowers the e(g) manifold energy, whereas the divacancy configuration lowers the t(2g) manifold energy.
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| 9. |
- Shukla, Vivekanand, 1988-, et al.
(författare)
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Rectifying behavior in twisted bilayer black phosphorus nanojunctions mediated through intrinsic anisotropy
- 2020
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 2:4, s. 1493-1501
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Tidskriftsartikel (refereegranskat)abstract
- We explore the possibility of using van der Waals bonded heterostructures of stacked together 2D bilayer black phosphorus (BP) for nanoscale device applications. The electronic properties of BP in AA stacking and 90 degrees twisted are studied with density functional theory. Furthermore, we study the homogeneous nanojunction architecture of BP to use its anisotropic properties. Using the first principles simulations along with the NEGF approach, we calculate the quantum transport properties of the nanojunction setup. The interlayer direction dependent current characteristics are explained in different setups. Our result revealed that the 90 degrees twisted nanojunction device would be a potential rectifier despite having no p-n junction characteristics only due to the intrinsic anisotropy of the material, making tunneling between armchair- and zigzag-directional BP sheets asymmetric.
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| 10. |
- Tsuppayakorn-aek, Prutthipong, et al.
(författare)
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Route to high-T-c superconductivity of BC7 via strong bonding of boron-carbon compound at high pressure
- 2020
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- We have analyzed the compositions of boron-carbon system, in which the BC7 compound is identified as structural stability at high pressure. The first-principles calculation is used to identify the phase diagram, electronic structure, and superconductivity of BC7. Our results have demonstrated that the BC7 is thermodynamically stable in the diamond-like P4m2 structure at a pressure above 244 GPa, and under temperature also. Feature of chemical bonds between B and C atoms is presented using the electron localization function. The strong chemical bonds in diamond-like P4m2 structure are covalent bonds, and it exhibits the s-p hybridization under the pressure compression. The Fermi surface shape displays the large sheet, indicating that the diamond-like P4m2 phase can achieve a high superconducting transition temperature (T-c). The outstanding property of BC7 at 250 GPa has manifested very hig h-T-c of superconductivity as 164 K, indicating that the carbon-rich system can induce the high-T-c value as well.
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