| 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. |
- Grigoriev, Anton, et al.
(författare)
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Electron transport in stretched monoatomic gold wires
- 2006
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 97, s. 236807-
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Tidskriftsartikel (refereegranskat)abstract
- The conductance of monoatomic gold wires containing 3-7 gold atoms has been obtained from ab initio calculations. The transmission is found to vary significantly depending on the wire stretching and the number of incorporated atoms. Such oscillations are determined by the electronic structure of the one-dimensional (1D) part of the wire between the contacts. Our results indicate that the conductivity of 1D wires can be suppressed without breaking the contact.
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| 5. |
- Bovornratanaraks, Thiti, et al.
(författare)
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Ground-state structure of semiconducting and superconducting phases in xenon carbides at high pressure
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The 'missing Xe paradox' is one of the phenomena at the Earth's atmosphere. Studying the 'missing Xe paradox' will provide insights into a chemical reaction of Xe with C. We search the ground-state structure candidates of xenon carbides using the Universal Structure Predictor: Evolutionary Xtallography (USPEX) code, which has been successfully applied to a variety of systems. We predict that XeC2 is the most stable among the convex hull. We find that the I((4) over bar)2m structure of XeC2 is the semiconducting phase. Accurate electronic structures of tetragonal XeC2 have been calculated using a hybrid density functionals HSE06, which gives larger more accurate band gap than a GGA-PBE exchange-correlation functional. Specifically, we find that the I((4) over bar)2m structure of XeC2 is a dynamically stable structure at high pressure. We also predict that the P6/mmm structure of XeC2 is the superconducting phase with a critical temperature of 38 K at 200 GPa. The ground-state structure of xenon carbides is of critical importance for understanding in the missing Xe. We discuss the inference of the stable structures of XeC2. The accumulation of electrons between Xe and C led to the stability by investigating electron localization function (ELF).
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| 6. |
- Hu, Shuanglin, et al.
(författare)
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Optical properties of Mg-doped VO2 : Absorption measurements and hybrid functional calculations
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:20, s. 201902-
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Tidskriftsartikel (refereegranskat)abstract
- Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < <(h)over bar>omega < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.
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| 7. |
- Lykissa, Iliana, et al.
(författare)
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Electronic density-of-states of amorphous vanadium pentoxide films : Electrochemical data and density functional theory calculations
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:18, s. 183701/1-/5
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of V2O5 were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V2O5. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.
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| 8. |
- Ramzan, Muhammad, 1971-, et al.
(författare)
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Molecular dynamics study of amorphous Ga-doped In2O3 : A promising material for phase change memory devices
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:7, s. 072113-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we employ the ab-initio molecular dynamics simulations, within the framework of density functional theory, to construct and characterize the amorphous structure of gallium-doped indium oxide. The electronic properties of amorphous and crystalline structures of Ga:In2O3 are investigated and compared by calculating the density of states, radial distribution function, bond angle distribution, and Bader charge analysis. We observe the band gap closure in amorphous structure, which corresponds to semiconductor to metallic transition in this material on amorphization. Our calculated results show the same characteristics of Ga:In2O3 with other phase change memory (PCM) materials available in literature and suggest it a promising candidate for PCM devices.
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| 9. |
- 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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| 10. |
- Wang, Baochang, et al.
(författare)
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Optical and electronic properties of nanosized BiTaO4 and BiNbO4 photocatalysts : Experiment and theory
- 2014
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 251:5, s. 1034-1039
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Tidskriftsartikel (refereegranskat)abstract
- Nanosized BiTaO4 and BiNbO4 were prepared by the citrate method. The electronic and optical properties of BiTaO4 and BiNbO4 have been investigated by means of photo-acoustic spectroscopy (PAS), X-ray photo-electron spectroscopy (XPS), and first-principles calculations based on density functional theory. The measured valence band (from XPS) of both materials agreed well with the theoretical findings. It was also found that the calculated optical properties such as dynamical dielectric function and optical absorption spectra are in good agreement with the experimental findings. According to the absorption spectra, the absorption edges of BiNbO4 and BiTaO4 are located at 370 and 330nm, respectively. Both phases have the ability to harvest UV light and relatively high surface area to volume ratio and can be used as UV/visible light-driven photocatalysts.
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