| 1. |
- Baran, Jakub, 1980, et al.
(författare)
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On the stability of single-walled carbon nanotubes and their binding strengths
- 2012
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Ingår i: Theoretical Chemistry Accounts. - : Springer Science and Business Media LLC. - 1432-881X .- 1432-2234. ; 131:9, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the relative stability of hydrogen-terminated single-walled carbon nanotubes (SWNTs) segments, and open-ended SWNT fragments of varying diameter and chirality that are present at the interface of the catalytic metal particles during growth. We have found that hydrogen-terminated SWNTs differ by < 1 eV in stability among different chiralities, which presents a challenge for selective and property-controlled growth. In addition, both zigzag and armchair tubes can be the most stable chirality of hydrogen-terminated SWNTs, which is a fundamental obstacle for property-controlled growth utilizing thermodynamic stability. In contrast, the most armchair-like open-ended SWNTs segments are always the most stable ones, followed in sequence by chiral index up to the least stable zigzag segments. We explain the ordering by triple bond stabilization of the carbon dangling bonds at the open ends, which is a fragment stabilization effect that is only manifested when all bonds between two layers are broken. We show convincingly that the bond strength difference between zigzag and armchair tubes is not present when individual bonds are broken or formed. © Springer-Verlag 2012.
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| 2. |
- 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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| 3. |
- Khossossi, Nabil, et al.
(författare)
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Exploring the Possibility of beta-Phase Arsenic-Phosphorus Polymorph Monolayer as Anode Materials for Sodium-Ion Batteries
- 2020
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Ingår i: Advanced Theory and Simulations. - : Wiley-VCH Verlag. - 2513-0390. ; 3:8
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Tidskriftsartikel (refereegranskat)abstract
- Graphite anode have shown commercial success for over two decades, since the start of their use in commercial Li-ion batteries, due to their high practical specific capacity, conductivity, and low lithiation potential. Graphite is to a large extent thermodynamically unfavorable for sodium-ion intercalation and thus limits advancement in Na-ion batteries. In this work, a beta-phase arsenic-phosphorus monolayer is studied, which has recently been predicted to have semiconducting behavior and to be dynamically stable. First-principles calculations based on density functional theory are used to explore the role of beta-AsP monolayer as a negative electrode for Na-ion batteries. Cohesive energy, phonon spectrum, and molecule dynamics simulations confirm the thermodynamic stability and the possibility of experimentally synthesizing this material. The Na-ion adsorption-energies are found to be high (>-1.2 eV) on both sides (As- and P-side). The ultra-fast energy barriers for Na (0.046/0.053 V) over both sides imply high diffusion of Na-ions on the surfaces of beta-AsP. During the evaluation of Na-ion anode performance, the fully sodiated state is found to be Na2AsP, which yields a high theoretical-specific capacity of 506.16 mAh g(-1)and low average sodiation potential of 0.43 V versus Na/Na+.
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| 4. |
- Khossossi, Nabil, et al.
(författare)
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Rational Design of 2D h-BAs Monolayer as Advanced Sulfur Host for High Energy Density Li-S Batteries
- 2020
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 3:8, s. 7306-7317
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of compact lithium-sulfur (Li-S) batteries with improved performances is becoming one of the most desirable aspects of future energy technologies. Beyond Li-ion batteries, Li-S is of great relevance to follow as it adapts to the specificity of each application. It is among the most suitable elements for high-performance energy storage systems, given its high theoretical capacity (1674 mA h g(-1)) and energy density (2600 W h kg(-1)) relative to Li-ion batteries (300 W h kg(-1)). Nevertheless, the high-cell polarization and the shuttle effect constitute an enormous challenge toward the concrete applications of Li-S batteries. In the framework of this work, density functional theory calculations have been carried out to analyze the potential of h-BAs nanosheets as a promising host material for Li-S batteries. Binding and electronic characteristics of lithium polysulfides (LiPSs) adsorbed on h-BAs surface have been explored. Reported findings highlight the potential of the hBAs monolayer as a moderate host material, given that the binding energies of different LiPSs vary from 0.47 to 3.55 eV. More detailed analysis of the complex binding mechanisms is carried out by investigating the components of van der Waals physical/chemical interactions. The defected surface of the h-BAs monolayer has optimum binding energies with LiPSs for Li-S batteries. All these findings provide valuable insights into the binding and electronic characteristics of the h-BAs monolayer as a moderate host material for Li-S batteries.
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| 5. |
- 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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| 6. |
- Prasongkit, Jariyanee, et al.
(författare)
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Cumulene molecular wire conductance from first principles
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 81:11
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Tidskriftsartikel (refereegranskat)abstract
- We present first principles calculations of current-voltage characteristics (IVC) and conductance of Au(111):S-2-cumulene-S-2:Au(111) molecular wire junctions with realistic contacts. The transport properties are calculated using full self-consistent ab initio nonequilibrium Green's function density-functional theory methods under external bias. The conductance of the cumulene wires shows oscillatory behavior depending on the number of carbon atoms (double bonds). Among all conjugated oligomers, we find that cumulene wires with odd number of carbon atoms yield the highest conductance with metalliclike ballistic transport behavior. The reason is the high density of states in broad lowest unoccupied molecular orbital levels spanning the Fermi level of the electrodes. The transmission spectrum and the conductance depend only weakly on applied bias, and the IVC is nearly linear over a bias region of +/- 1 V. Cumulene wires are therefore potential candidates for metallic connections in nanoelectronic applications.
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| 7. |
- Prasongkit, Jariyanee, et al.
(författare)
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Interference effects in phtalocyanine controlled by H-H tautomerization: Potential two-terminal unimolecular electronic switch
- 2011
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 84:16, s. 165437-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the electrical transport properties of two hydrogen tautomer configurations of phthalocyanine (H(2)Pc) connected to cumulene and gold leads. Hydrogen tautomerization affects the electronic state of H(2)Pc by switching the character of molecular orbitals with the same symmetry close to the Fermi level. The near degeneracy between the HOMO and HOMO-1 leads to pronounced interference effects, causing a large change in current for the two tautomer configurations, especially in the low-bias regime. Two types of planar junctions are considered: cumulene-H(2)Pc-cumulene and gold-H(2)Pc-gold. Both demonstrate a prominent difference in molecular conductance between ON and OFF states. In addition, junctions with gold leads show pronounced negative differential resistance (NDR) at high bias voltage, as well as weak NDR at intermediate bias.
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| 8. |
- Singh, Deobrat, et al.
(författare)
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Carbon-phosphide monolayer with high carrier mobility and perceptible: I - V response for superior gas sensing
- 2020
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1369-9261 .- 1144-0546. ; 44:9, s. 3777-3785
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Tidskriftsartikel (refereegranskat)abstract
- Monolayered carbon phosphide (CP), with semi-metallic electrical conductivity and graphene-like Dirac cone responses, has attracted significant attention from the advanced nanoelectronics community, for use in gas sensing devices. The CP monolayer exhibits semi-metallic behavior in the x-direction and semi-conducting behavior in the y-direction. With the presence of graphene-like Dirac cones, it holds highly anisotropic carrier mobility characteristics. Here, we introduce the first-principle theoretical calculations for understanding the adsorption mechanism of different gas molecules-CO, CO2, NH3, NO and NO2-on the monolayer for electronic sensing devices. The binding strengths of these gas molecules adsorbed on the CP layer are much stronger than for other reported two-dimensional materials, such as graphene, blue phosphorene, germanene, etc. Additionally, the charge transfer analysis also supported an enhanced binding strength due to the sufficient amount of charge sharing between the CP monolayer and gas molecules. We further present an extensive study about the transport properties of CP monolayer sensor devices with electrodes made out of identical materials. The transmission characteristics, the density of states, and I-V response are supported by analysis of the charge distribution of the CP monolayer upon adsorption of CO, CO2, NH3, NO and NO2. Molecules have been calculated using density functional theory and non-equilibrium Green's function. The presented theoretical investigations reveal that the CP monolayer-based device exhibits improved characteristics and could be the foundation towards constructing highly sensitive nanosensor devices.
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| 9. |
- Singh, Deobrat, et al.
(författare)
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Harnessing the unique properties of MXenes for advanced rechargeable batteries
- 2021
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Ingår i: JPhys Energy. - : IOP Publishing. - 2515-7655. ; 3:1
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Forskningsöversikt (refereegranskat)abstract
- In recent years, two-dimensional MXenes have been emerged as potential electrode materials for rechargeable batteries due to their unique properties such as exceptional safety, significant interlayer spacing, environmental flexibility, large surface area, high electrical conductivity, and excellent thermal stability. This review examined all of the recent advances in the field of MXenes and their composites (hybrid structures), which are found to be useful for the electrochemical applications of advanced rechargeable batteries. The main focus of this review is on metal-ion batteries and lithium-sulfur (Li-S) batteries. It is intended to show that the combination of recent improvements in the synthesis and characterization, greater control of the interlayer distance, and new MXene composites, together serve as an emerging and potential way for energy storage applications.
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| 10. |
- Singh, Deobrat, et al.
(författare)
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Optical excitations and thermoelectric properties of two-dimensional holey graphene
- 2020
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Ingår i: PHYSICAL REVIEW B. - : American Physical Society (APS). - 2469-9969 .- 2469-9950. ; 102:7
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Tidskriftsartikel (refereegranskat)abstract
- Recently, holey graphene (HG) was synthesized successfully at atomic precision with regard to hole size and shape, which indicates that HG has interesting physical and chemical properties for energy and environmental applications. The shaping of the pores also transforms semimetallic graphene into semiconductor HG, which opens new doors for its use in electronic applications. We investigated systematically the structural, electronic, optical, and thermoelectric properties of HG structure using first-principles calculations. HG was found to have a direct band gap of 0.65 eV (PBE functional) and 0.95 eV (HSE06 functional); the HSE06 functional is in good agreement with experimental results. For the optical properties, we used single-shot G(0)W(0) calculations by solving the Bethe-Salpeter equation to determine the intralayer excitonic effects. From the absorption spectrum, we obtained an optical gap of 1.28 eV and a weak excitonic binding energy of 80 meV. We found large values of thermopower of 1662.59 mu V/K and a better electronic figure of merit, ZT(e), of 1.13 from the investigated thermoelectric properties. Our investigations exhibit strong and broad optical absorption in the visible light region, which makes monolayer HG a promising candidate for optoelectronic and thermoelectric applications.
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