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Journal ArticleDOI: 10.1039/D0CP06213H

Electronic and optical properties of two-dimensional heterostructures and heterojunctions between doped-graphene and C- and N-containing materials.

04 Mar 2021-Physical Chemistry Chemical Physics (The Royal Society of Chemistry)-Vol. 23, Iss: 8, pp 4865-4873
Abstract: The electronic and optical properties of vertical heterostructures (HTSs) and lateral heterojunctions (HTJs) between (B,N)-codoped graphene (dop@Gr) and graphene (Gr), C3N, BC3 and h-BN monolayers are investigated using van der Waals density functional theory calculations. We have found that all the considered HTSs are energetically and thermally feasible at room temperature, and therefore they can be synthesized experimentally. The dop@Gr/Gr, BC3/dop@Gr and BN/dop@Gr HTSs are semiconductors with direct bandgaps of 0.1 eV, 80 meV and 1.23 eV, respectively, while the C3N/dop@Gr is a metal because of the strong interaction between dop@Gr and C3N layers. On the other hand, the dop@Gr-Gr and BN-dop@Gr HTJs are semiconductors, whereas the C3N-dop@Gr and BC3-dop@Gr HTJs are metals. The proposed HTSs can enhance the absorption of light in the whole wavelength range as compared to Gr and BN monolayers. The applied electric field or pressure strain changes the bandgaps of the HTSs and HTJs, indicating that these HTSs are highly promising for application in nanoscale multifunctional devices.

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Topics: Graphene (52%), Heterojunction (51%)

8 results found

Open accessJournal ArticleDOI: 10.1016/J.APSUSC.2021.149862
Abstract: The two dimensional MoSi2N4 (MSN) monolayer exhibiting rich physical and chemical properties was synthesized for the first time last year. We have used the spin-polarized density functional theory to study the effect of different types of point defects on the structural, electronic, and magnetic properties of the MSN monolayer. Adsorbed, substitutionally doped (at different lattice sites), and some kind of vacancies have been considered as point defects. The computational results show all defects studied decrease the MSN monolayer band gap. We found out the H-, O-, and P-doped MSN are n-type conductors. The arsenic-doped MSN, and MSN with vacancy defects have a magnetic moment. The MSN with a Si vacancy defect is a half-metallic which is favorable for spintronic applications, while the MSN with a single N vacancy or double vacancy (N + S) defects are metallic, i.e., beneficial as spin filters and chemical sensors.

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Topics: Vacancy defect (60%), Monolayer (53%)

21 Citations

Journal ArticleDOI: 10.1063/5.0044976
Abstract: Recently, a two-dimensional (2D) MoSi 2N 4 (MSN) structure has been successfully synthesized [Hong et al., Science 369(6504), 670–674 (2020)]. Motivated by this result, we investigate the structural, electronic, and optical properties of MSN monolayer (MSN-1L) and bilayer (MSN-2L) under the applied electric field (E-field) and strain using density functional theory calculations. We find that the MSN-2L is a semiconductor with an indirect bandgap of 1.60 (1.80) eV using Perdew–Burke–Ernzerhof (HSE06). The bandgap of MSN-2L decreases as the E-field increases from 0.1 to 0.6 V/A and for larger E-field up to 1.0 V/A the bilayer becomes metallic. As the vertical strain increases, the bandgap decreases; more interestingly, a semiconductor to a metal phase transition is observed at a strain of 12 %. Furthermore, the optical response of the MSN-2L is in the ultraviolet (UV) region of the electromagnetic spectrum. The absorption edge exhibits a blue shift by applying an E-field or a vertical compressive strain. The obtained interesting properties suggest MSN-2L as a promising material in electro-mechanical and UV opto-mechanical devices.

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Topics: Bilayer (57%), Absorption edge (52%), Band gap (51%) ... read more

13 Citations

Journal ArticleDOI: 10.1039/D1CP00317H
Mosayeb Naseri1, Asadollah Bafekry2, M. Faraji3, D.M. Hoat4  +4 moreInstitutions (8)
Abstract: Pure hydrogen production via water splitting is an ideal strategy for producing clean and sustainable energy. Two-dimensional (2D) cadmium chalcogenide single-layers with a tetragonal crystal structure, namely Tetra-CdX (X = S, Se, and Te) monolayers, are theoretically predicted by means of density functional theory (DFT). Their structural stability and electronic and optical properties are investigated. We find that Tetra-CdX single-layers are thermodynamically stable. Their stability decreases as we go down the 6A group in the periodic table, i.e., from X = S to Se, and Te which also means that the electronegativity decreases. All considered novel monolayers are indirect band gap semiconductors. Using the HSE06 functional the electronic band gaps of CdS, CdSe, and CdTe monolayers are predicted to be 3.10 eV, 2.97 eV, and 2.90 eV, respectively. The impact of mechanical strain on the physical properties was studied, which indicates that compressive strain increases the band gap and tensile strain decreases the band gap. The optical properties of the Tetra-CdX monolayers show the ability of these monolayers to absorb visible light. Due to the suitable band gaps and band edge positions of Tetra-CdX, these newly discovered 2D materials are promising for photocatalytic water splitting.

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Topics: Band gap (62%), Direct and indirect band gaps (62%), Photocatalytic water splitting (53%) ... read more

7 Citations

Journal ArticleDOI: 10.1016/J.MOLLIQ.2021.116126
Abstract: Recently, a series of organic structures formed by peptide self-assembly have been reported, among which stand out the peptide nanomembranes with promising applications in the energy storage field. In these applications, the nanomembranes can be subjected to high temperatures. Although the effects of temperature are well known in lipid membranes, in peptide ones they lack further investigation. In this sense, we present a study based on fully atomistic molecular dynamics simulation, which demonstrates the behavior of peptide membranes formed by Alanine (A) and Arginine (R) electrically charged and uncharged, A6R1+ and A6R, at temperatures of 300 K, 320 K, 340 K, 360 K, 380 K, 400 K, 420 K, 440 K, 460 K, 480 K, and 500 K. We report a detailed analysis based on the total average number of Hydrogen Bonds (HBs) between the residues and between the residues with the water molecules, as well as the average lifetime of each of these interactions. Our results demonstrate that a hydrogen-bond network is maintained in the range of temperature evaluated contributing to the stability of the peptide nanomembranes. The increase in temperature causes only a small variation in the total number of HBs, however, the HBs lifetime of these interactions is drastically affected by temperature, providing greater dynamics in the peptide-peptide interaction, favoring greater mobility of these molecules as the temperature rises, as confirmed by the Einstein's diffusion coefficient, also obtained in this study. The HBs results together with the Coulomb and vdW interactions, show that the membrane structures are quite stable in withstanding high temperatures, which may indicate a potential application in coatings, liquid separation, and especially in supercapacitors since the nanomembranes formed by A6R1+ and A6R peptide present pores in all 2D-material favoring a slight infiltration of ionic liquid in the material surface, which directly impacts energy storage efficiency.

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Topics: Membrane (51%)

3 Citations

Journal ArticleDOI: 10.1016/J.SPMI.2021.106944
Neelesh Gupta1, Rekha Verma1Institutions (1)
Abstract: Whenever a material is grown on a substrate, an external strain is induced on the material due to the lattice mismatch between the substrate and the material. Strain engineering plays an important role in tuning the electronic, vibrational and mechanical properties of a material by proper choice of lattice mismatch. We investigate the effect of biaxial strain on thermoelectric transport coefficients in low-buckled monolayer silicene using first principles study. The compressive strain shows the lattice instability while tensile strain shows stability with a small band-gap opening at the K-point. We systematically estimate the temperature dependent average relaxation time by calculating the electron-phonon coupling in silicene. Incorporation of the relaxation time in transport coefficients along with the effect of external strain increases the practicality of our investigations. The doped behaviour of silicene is also predicted using the rigid-band approximation. We find that with the applied tensile strain, the Seebeck coefficient and electronic thermal conductivity improves while the electrical conductivity and lattice thermal conductivity degrades slightly from its relaxed value.

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Topics: Silicene (62%), Strain engineering (62%), Seebeck coefficient (54%) ... read more

3 Citations


65 results found

Journal ArticleDOI: 10.1103/PHYSREVB.13.5188
Hendrik J. Monkhorst1, J.D. Pack1Institutions (1)
15 Jun 1976-Physical Review B
Abstract: A method is given for generating sets of special points in the Brillouin zone which provides an efficient means of integrating periodic functions of the wave vector. The integration can be over the entire Brillouin zone or over specified portions thereof. This method also has applications in spectral and density-of-state calculations. The relationships to the Chadi-Cohen and Gilat-Raubenheimer methods are indicated.

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Topics: Brillouin zone (62%)

42,677 Citations

Open accessJournal ArticleDOI: 10.1103/REVMODPHYS.81.109
Abstract: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

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Topics: Graphene nanoribbons (67%), Silicene (64%), Graphene (64%) ... read more

18,972 Citations

Journal ArticleDOI: 10.1002/JCC.20495
Stefan Grimme1Institutions (1)
Abstract: A new density functional (DF) of the generalized gradient approximation (GGA) type for general chemistry applications termed B97-D is proposed. It is based on Becke's power-series ansatz from 1997 and is explicitly parameterized by including damped atom-pairwise dispersion corrections of the form C(6) x R(-6). A general computational scheme for the parameters used in this correction has been established and parameters for elements up to xenon and a scaling factor for the dispersion part for several common density functionals (BLYP, PBE, TPSS, B3LYP) are reported. The new functional is tested in comparison with other GGAs and the B3LYP hybrid functional on standard thermochemical benchmark sets, for 40 noncovalently bound complexes, including large stacked aromatic molecules and group II element clusters, and for the computation of molecular geometries. Further cross-validation tests were performed for organometallic reactions and other difficult problems for standard functionals. In summary, it is found that B97-D belongs to one of the most accurate general purpose GGAs, reaching, for example for the G97/2 set of heat of formations, a mean absolute deviation of only 3.8 kcal mol(-1). The performance for noncovalently bound systems including many pure van der Waals complexes is exceptionally good, reaching on the average CCSD(T) accuracy. The basic strategy in the development to restrict the density functional description to shorter electron correlation lengths scales and to describe situations with medium to large interatomic distances by damped C(6) x R(-6) terms seems to be very successful, as demonstrated for some notoriously difficult reactions. As an example, for the isomerization of larger branched to linear alkanes, B97-D is the only DF available that yields the right sign for the energy difference. From a practical point of view, the new functional seems to be quite robust and it is thus suggested as an efficient and accurate quantum chemical method for large systems where dispersion forces are of general importance.

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18,839 Citations

Open accessJournal ArticleDOI: 10.1103/PHYSREVLETT.105.136805
Kin Fai Mak1, Changgu Lee2, James Hone1, Jie Shan3  +1 moreInstitutions (3)
Abstract: The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N=1,2,…,6 S-Mo-S monolayers have been investigated by optical spectroscopy Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace the effect of quantum confinement on the material's electronic structure With decreasing thickness, the indirect band gap, which lies below the direct gap in the bulk material, shifts upwards in energy by more than 06 eV This leads to a crossover to a direct-gap material in the limit of the single monolayer Unlike the bulk material, the MoS₂ monolayer emits light strongly The freestanding monolayer exhibits an increase in luminescence quantum efficiency by more than a factor of 10⁴ compared with the bulk material

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Topics: Monolayer (61%), Direct and indirect band gaps (59%), Photoconductivity (57%) ... read more

11,041 Citations

Open accessJournal ArticleDOI: 10.1038/NNANO.2010.279
Abstract: Two-dimensional materials are attractive for use in next-generation nanoelectronic devices because, compared to one-dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two-dimensional material is graphene, both because of its rich physics and its high mobility. However, pristine graphene does not have a bandgap, a property that is essential for many applications, including transistors. Engineering a graphene bandgap increases fabrication complexity and either reduces mobilities to the level of strained silicon films or requires high voltages. Although single layers of MoS(2) have a large intrinsic bandgap of 1.8 eV (ref. 16), previously reported mobilities in the 0.5-3 cm(2) V(-1) s(-1) range are too low for practical devices. Here, we use a halfnium oxide gate dielectric to demonstrate a room-temperature single-layer MoS(2) mobility of at least 200 cm(2) V(-1) s(-1), similar to that of graphene nanoribbons, and demonstrate transistors with room-temperature current on/off ratios of 1 × 10(8) and ultralow standby power dissipation. Because monolayer MoS(2) has a direct bandgap, it can be used to construct interband tunnel FETs, which offer lower power consumption than classical transistors. Monolayer MoS(2) could also complement graphene in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.

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Topics: Graphene nanoribbons (62%), Phosphorene (56%), Graphene (56%) ... read more

10,809 Citations

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