Real-space exciton distribution in strained-siligraphene g-SiC7 (original) (raw)
Related papers
Journal of Nepali Physical Society, 2021
Using the first principles calculation, we investigated the structural, electronic, and straindependent optical properties of the two-dimensional hexagonal Silicon Carbide (SiC) Monolayer. We found that the biaxial compressive strain loading gradually changes the direct bandgap SiC into indirect bandgap semiconductor. The compressive strain increases the bandgap but reduces the values of static dielectric constant and refractive index. Conversely, the biaxial tensile strain loading decreases the bandgap but increases the value of static dielectric constant and refractive index. The result shows that the electronic and optical properties of SiC can be engineered to the desired value by applying strain. The large bandgap issue for the SiC monolayer is limiting its uses in different applications which can be overcome with the help of biaxial strain.
Effect of uniaxial strain on the excitonic properties of monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">mml:mrowmml:msub<mml:mi mathvariant="normal">Cmml:mn3<mml:mi mathvariant="normal">N : A symmetry-based anal...
Physical review, 2023
In recent years, the application of mechanical stress has become a widespread experimental method to tune the electronic and optical properties of two-dimensional (2D) materials. In this work, we investigate the impact of uniaxial tensile strain along zigzag and armchair directions on the excitonic properties of graphene-like C 3 N, a single-layer indirect-gap material with relevant mechanical and optical properties. To do that, we develop a tightbinding Bethe-Salpeter equation framework based on a Wannier-function description of the frontier bands of the system, and use it to compute both dark and bright excitons of C 3 N for different applied strain configurations. Then, we use this model approach to classify excitons of pristine and strained C 3 N according to the crystal symmetry and to explain the appearance of bright excitons with intense optical anisotropy in strained C 3 N, even at small strains. Finally, the effect of strain on the exciton dispersion at small center-of-mass momenta is discussed, with special focus on the implications for 2D linear-nonanalytic dispersions.
Ab initio study of electronic and optical behavior of two-dimensional silicon carbide
Journal of Materials Chemistry C, 2013
Two-dimensional graphene-like silicon carbide (2d-SiC) has emerged as an intriguing new class of layered nanostructure. Using density functional theory, key electronic and optical properties of 2d-SiC nanosheets, in particular, of mono- and bilayer 2d-SiC, are investigated. The properties of these nanosheets are found to be highly dependent on their physical thickness and geometric configuration. Multilayer 2d-SiC exhibits an indirect bandgap. We find that monolayer 2d-SiC, on the other hand, has a direct bandgap (∼2.5 eV) that can be tuned through in-plane strain. We also show that the optical conductivity of multilayer 2d-SiC is sensitive to the interlayer spacing. The results suggest that unlike graphene, silicene and even multilayer 2d-SiC, monolayer 2d-SiC could be a good candidate for optoelectronic devices such as light-emitting diodes.
2008
Using first-principles method, we calculate the electronic band structure of biaxially strained silicon, from which we analyze the change in electron and hole effective mass as a function of strain and determine the mobility of electrons and holes in the biaxially strained silicon based on Boltzmann transport theory. We found that electron mobility increases with tensile strain and decreases with compressive strain. Such changes are mainly caused by a strain-induced change in electron effective mass, while the suppression of intervalley scattering plays a minor role. On the other hand, the hole mobility increases with both signs of strain and the effect is more significant for compressive strain because the hole effective mass decreases with compressive strain but increases with tensile strain. The strain-induced suppression of interband and intraband scatterings plays also an important role in changing the hole mobility.
Excitonic effects in the optical properties of a SiC sheet and nanotubes
2011
The quasiparticle band structure and optical properties of single-walled zigzag and armchair SiC nanotubes (SiC-NTs) as well as single SiC sheet are investigated by ab initio many-body calculations using the GW and the GW plus Bethe-Salpeter equation (GW+BSE) approaches, respectively. Significant GW quasiparticle corrections of more than 1.0 eV to the Kohn-Sham band gaps from the local density approximation (LDA) calculations are found. The GW self-energy corrections transform the SiC sheet from a indirect LDA band gap to a direct band gap material. Furthermore, the quasiparticle band gaps of SiC-NTs with different chiralities behave very differently as a function of tube diameter, and this can be attributed to the difference in the curvature-induced orbital rehybridization between the different chiral nanotubes. The calculated optical absorption spectra are dominated by discrete exciton peaks due to exciton states with large binding energy up to 2.0 eV in the SiC sheet and SiC-NTs. The formation of strongly bound excitons is attributed to the enhanced electron-hole interaction in these low dimensional systems. Remarkably, the excited electron amplitude of the exciton wavefunction is found to peak on the Si atoms near the hole position (which is on the C site) in the zigzag SiC-NTs, indicating a charge transfer from an anion (hole) to its neighboring cations by photoexcitation. In contrast, this pronounced peak structure disappear in the exciton wavefunction in the armchair SiC-NTs. Furthermore, in the armchair SiC-NTs, the bound exciton wavefunctions are more localized and also strongly cylindrically asymmetric. The large excitation energy of ∼ 3.0 eV of the first bright exciton with no dark exciton below it, suggests that the small-radius armchair SiC-NTs be useful for optical devices working in the UV regime. On the other hand, the zigzag SiC-NTs have many dark excitons below the first bright exciton and hence may have potential applications in tunable optoelectric devices ranging from infrared to UV frequencies by external perturbations.
Uniaxial strain-induced mechanical and electronic property modulation of silicene
Nanoscale research letters, 2014
We perform first-principles calculations of mechanical and electronic properties of silicene under uniaxial strains. Poisson's ratio and the rigidity of silicene show strong chirality dependence under large uniaxial strains. The ultimate strains of silicene with uniaxial strain are smaller than those with biaxial strain. We find that uniaxial strains induce Dirac point deviation from the high-symmetry points in the Brillouin zone and semimetal-metal transitions. Therefore, no bandgap opens under the uniaxial strain. Due to its peculiar structure and variable sp (3)/sp (2) ratio of the chemical bond, the deviation directions of Dirac points from the high-symmetry points in the Brillouin zone and variation of Fermi velocities of silicene exhibit significant difference from those of graphene. Fermi velocities show strong anisotropy with respect to the wave vector directions and change slightly before the semimetal-metal transition. We also find that the work function of silicene in...
Uniaxially stressed silicon: Fine structure of the exciton and deformation potentials
Physical Review B, 1978
The splitting of the indirect exciton in Si is measured, at the TO-phonon-assisted threshold, as a zerostress extrapolation of the multiplet structure due to uniaxial stresses applied in the [001] direction. The validity of the. method is warranted by a theoretical analysis of the exciton wave functions and energy levels under the combined influence of mass anisotropy and external perturbation. For the splitting, a value of 0.29+0.05 meV is found and compared with the latest theoretical estimate of the mass-anisotropy effect which includes coupling with the split-off valence band; the measured splitting, however, may include a contribution from exchange interaction, The intensities of the exciton components for moderately high stress are quite consistent with those calculated for an indirect transition mechanism involving only two intermediate states I', & and hz which can produce interference. In the limit of zero stress, a ratio of the intensities of the doublet components q = 5.7+0.5 is determined. The experiment allows also a direct measurement of the deformation potentials, giving, results in very good agreement with pseudopotential calculations.
Applied Physics Letters, 2007
We present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface. Low voltage topographic images reveal fine, atomic-scale carbon networks, whereas higher bias images are dominated by emergent spatially inhomogeneous large-scale structure similar to a carbon-rich reconstruction of SiC(0001). STS spectroscopy shows a ~100meV gap-like feature around zero bias for both monolayer and bilayer graphene/SiC, as well as significant spatial inhomogeneity in electronic structure above the gap edge. Nanoscale structure at the SiC/graphene interface is seen to correlate with observed electronic spatial inhomogeneity. These results are important for potential devices involving electronic transport or tunneling in graphene/SiC.
Evidence of Structural Strain in Epitaxial Graphene Layers on 6H-SiC(0001)
Physical Review Letters, 2008
The early stages of epitaxial graphene layer growth on the Si-terminated 6H-SiC(0001) are investigated by Auger electron spectroscopy (AES) and depolarized Raman spectroscopy. The selection of the depolarized component of the scattered light results in a significant increase in the C-C bond signal over the second order SiC Raman signal, which allows to resolve submonolayer growth, including individual, localized C=C dimers in a diamond-like carbon matrix for AES C/Si ratio of ∼3, and a strained graphene layer with delocalized electrons and Dirac single-band dispersion for AES C/Si ratio >6. The linear strain, measured at room temperature, is found to be compressive, which can be attributed to the large difference between the coefficients of thermal expansion of graphene and SiC. The magnitude of the compressive strain can be varied by adjusting the growth time at fixed annealing temperature.
Local enhancement of inelastic tunnelling in epitaxial graphene on SiC(0001)
physica status solidi (b), 2010
We have measured the elastic and inelastic tunnelling properties of epitaxial graphene on SiC(0001) using cryogenic scanning tunnelling spectroscopy. We find that the dominant inelastic channel of the out‐of‐plane acoustic graphene phonon at 70 mV is spatially localized to particular regions of the graphene–SiC system that contain localized states. At these locations the maximum inelastic tunnelling channel reaches up to half of the total tunnelling current. The local enhancement of the inelastic tunnelling is found at the localized electron states of the graphene/SiC interface layer. Nonequilibrium Green's function formalism theory calculations indicate that this intense inelastic channel arises from graphene phonon modes strongly coupled to narrow electron states.