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Imaging Chladni figure of plasmonic charge density wave in real space
摘要： The future photonic age largely depends on our ability to manipulate optical waves in confined systems. Particularly, understanding the behavior of plasmonic charge density wave (p-CDW) in optical resonators is vital for engineering 2D plasmonic devices. In this study, the standing p-CDW on the surface of a gold triangle resonator is examined through diffraction limited all-optical far field power loss microscopy. The scattering light map captured by this microscopy, named plasmonic Chladni figure, is directly proportional to the entire in-plane photonic local density of state. The theoretical model of plasmonic Chladni figure proposed in this study is related to the 2D standing p-CDW node pattern, which is similar to the mechanical Chladni but follows a special node selection rule. Investigating the plasmonic Chladni phenomenon provides an in-depth understanding of fundamental plasmonic physics, plasmonic chemistry, and presents various possibilities for plasmonic application, such as 2D dimensional SPP waveguide, plasmonic computing, hot electron based chemistry, light energy harvest and so on.
关键词： photonic local density of states,standing wave,electrochemical charging,plasmonic resonator,plasmonic charge density wave,plasmonic Chladni figure
更新于2025-09-11 14:15:04
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revealed by resonant photoelectron spectroscopy
摘要： Resonant photoelectron spectroscopy at the Co and Mn 2p core absorption edges of half-metallic Co2MnGe has been performed to determine the element-speci?c density of states (DOS). A signi?cant contribution of the Mn 3d partial DOS near the Fermi level (EF) was clari?ed by measurement at the Mn 2p absorption edge. Further analysis by ?rst-principles calculation revealed that it has t2g symmetry, which must be responsible for the electrical conductivity along the line perpendicular to the ?lm plane. The dominant normal Auger contribution observed at the Co 2p absorption edge indicates delocalization of photoexcited Co 3d electrons. The difference in the degrees of localization of the Mn 3d and Co 3d electrons in Co2MnGe is explained by the ?rst-principles calculation. Our ?ndings of the element-/orbital-speci?c electronic states near EF will pave the way for future interface design of magnetic tunneling junctions to overcome the temperature-induced reduction of the magnetoresistance.
关键词： first-principles calculation,magnetic tunneling junctions,normal Auger contribution,half-metallic Co2MnGe,magnetoresistance,Resonant photoelectron spectroscopy,Mn 3d partial DOS,element-speci?c density of states,electrical conductivity
更新于2025-09-11 14:15:04
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Electronic and structural properties of functionalized BN-doped(6,3) chiral SWCNT: A DFT study
摘要： Effect of functionalization of BN-doped (6,3) Chiral single walled carbon nanotubes by different nitrogen containing nucleophilic groups on their electronic properties was investigated by DFT method at B3LYP level of the theory. The binding energies for all the studied systems were between -8.70 and -15.06 kcal/mol and are in the order imidazole >Pyrazole > ammonia > pyridine, which is analogous to the pKa. Imidazole attached tube shows a smaller energy gap, 1.50 eV, respect to an isolated BN-doped (6,3) Chiral single walled carbon nanotube, 1.64 eV. For the other situations, change of the energy gaps was not considerable, which is in agreement with the results obtained for the densities of states. The natural bond orbital analysis was performed.
关键词： Functionalized Nanotube,nucleophilic groups,pyramidalization,BN Doped,Density of States
更新于2025-09-11 14:15:04
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Influence of Crystal Structure and 3d Impurities on the Electronic Structure of the Topological Material Cd3As2
摘要： This paper presents a theoretical study of the effects of crystal structure and Mn and Co substitutions for Cd on the electronic structure of the topological material Cd3As2. We have carried out density functional theory calculations of the band structure and density of states in tetragonal and cubic Cd3As2, as well as in Cd3 – xMnxAs2 and Cd3 – xCoxAs2 crystals. The results indicate that the band structure of the cubic Cd3As2 phase differs significantly from that of a Dirac semimetal, characteristic of the tetragonal phase. It has also been shown that, after Co substitution for 1/24 of the Cd atoms, the structure of the density of 3d electron states is similar to that of the density of states in the magnetic semiconductor Cd3 – xMnxAs2, with a characteristic minimum at the Fermi energy. At the same time, in the case of analogous Mn substitution for Cd, the density of d-electron states has no such minimum.
关键词： Mn,density functional theory (DFT) calculations,magnetic semiconductors,topological materials,Co,Cd3As2,Dirac semimetal,band structure,density of states (DOS)
更新于2025-09-10 09:29:36
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Efficient and quantitative analysis of photon density of states for two-dimensional photonic crystals with omnidirectional light propagation
摘要： Omnidirectional light propagation in two-dimensional (2D) photonic crystals (PCs) has been investigated by extending the formerly developed 2D finite element analysis (FEA) of in-plane light propagation in which the corresponding band structure (BS) and photon density of states (PDOS) of 2D PCs with complex geometry configurations had been calculated more accurately by using an adaptive FEA in real space for both the transverse electric (TE) and transverse magnetic (TM) modes. In this work, by adopting a wave-guiding theory under the consideration of translational symmetry, the omnidirectional PDOS corresponding to both the radiative and evanescent waves can be calculated efficiently based on the in-plane dispersion relations of both TE and TM modes within the irreducible Brillouin zone. We demonstrate that the complete band gaps shown by previous work considering only the radiative modes will be closed by including the contributions of the evanescent modes. These results are of general importance and relevance to the spontaneous emission by an atom or to dipole radiation in 2D periodic structures. In addition, it may serve as an efficient approach to identifying the existence of a complete photonic band gap in a 2D PC instead of using time-consuming three-dimensional BS calculations.
关键词： two-dimensional photonic crystals,radiative and evanescent waves,finite element analysis,photon density of states,omnidirectional light propagation
更新于2025-09-10 09:29:36
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Atomic and electronic structure of the Si(331)-(12 × 1) surface
摘要： We report on the investigation of the atomic and electronic structures of a clean Si(331)-(12 × 1) surface using a first-principles approach with both plane wave and strictly localized basis sets. Starting from the surface structure proposed by Zhachuk and Teys [Phys. Rev. B 95, 041412(R) (2017)], we develop significant improvements to the atomic model and localized basis set which are critical for the correct description of the observed bias dependence of scanning tunneling microscopy (STM) images. The size mismatch between the Si pentamers from the surface model and those seen by STM is explained within the context of the Tersoff-Hamann model. The energy barriers that separate different Si(331) buckled configurations were estimated, showing that the surface structure is prone to dynamic buckling at room temperature. It is found that empty electronic states on Si(331) are essentially localized on the pentamers with interstitials and under-coordinated Si sp2-like atoms between them, while filled electronic states are localized on under-coordinated Si sp3-like atoms and dimers on trenches. The calculated electronic density of states exhibits two broad peaks in the fundamental bandgap of Si: one near the valence band top and the other near the conduction band bottom. The resulting surface bandgap of 0.58 eV is in an excellent agreement with spectroscopy studies.
关键词： scanning tunneling microscopy,Si(331)-(12 × 1) surface,first-principles approach,electronic density of states,Tersoff-Hamann model,atomic and electronic structures,dynamic buckling
更新于2025-09-10 09:29:36
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Effects of nitrogen on the interface density of states distribution in 4H-SiC metal oxide semiconductor field effect transistors: Super-hyperfine interactions and near interface silicon vacancy energy levels
摘要： The performance of silicon carbide (SiC)-based metal-oxide-semiconductor field-effect transistors (MOSFETs) is greatly enhanced by a post-oxidation anneal in NO. These anneals greatly improve effective channel mobilities and substantially decrease interface trap densities. In this work, we investigate the effect of NO anneals on the interface density of states through density functional theory (DFT) calculations and electrically detected magnetic resonance (EDMR) measurements. EDMR measurements on 4H-silicon carbide (4H-SiC) MOSFETs indicate that NO annealing substantially reduces the density of near interface SiC silicon vacancy centers: it results in a 30-fold reduction in the EDMR amplitude. The anneal also alters post-NO anneal resonance line shapes significantly. EDMR measurements exclusively sensitive to interface traps with near midgap energy levels have line shapes relatively unaffected by NO anneals, whereas the measurements sensitive to defects with energy levels more broadly distributed in the 4H-SiC bandgap are significantly altered by the anneals. Using DFT, we show that the observed change in EDMR linewidth and the correlation with energy levels can be explained by nitrogen atoms introduced by the NO annealing substituting into nearby carbon sites of silicon vacancy defects.
关键词： MOSFETs,silicon carbide,NO anneals,interface density of states,DFT,EDMR
更新于2025-09-10 09:29:36
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On the influence of dilute charged impurity and perpendicular electric field on the electronic phase of phosphorene: Band gap engineering
摘要： Tuning the band gap plays an important role for applicability of 2D materials in the semiconductor industry. The present paper is a theoretical study on the band gap engineering using the electronic density of states (DOS) of phosphorene in the presence of dilute charged impurity and of a perpendicular electric field. The electronic DOS is numerically calculated using a combination of the continuum model Hamiltonian and the Green’s function approach. Our findings show that the band gap of phosphorene in the absence and presence of the perpendicular electric field decreases with increasing impurity concentration and/or impurity scattering potential. Further, we found that in the presence of opposite perpendicular electric fields, the electronic DOS of disordered phosphorene shows different changing behaviors stemming from the Stark effect: in the positive case the band gap increases with increasing electric-field strength; whereas in the negative case the band gap disappears. The latter, in turn, leads to the semiconductor-to-semimetal and semiconductor-to-metal phase transition for the case of strong impurity concentrations and strong impurity scattering potentials, respectively. The results can serve as a base for future applications in logic electronic devices.
关键词： Stark effect,perpendicular electric field,semiconductor-to-semimetal transition,phosphorene,band gap engineering,electronic density of states,semiconductor-to-metal transition,dilute charged impurity
更新于2025-09-10 09:29:36
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First principle calculations of electronic, band structural, and optical properties of BixSr1-xTiO3 perovskite
摘要： Based on the first-principles plane-wave ultrasoft pseudopotential method, we set up models of perovskite-type oxides BixSr1-xTiO3 (x=0, 0.25, 0.5, 0.625, 1), and the geomertry optimization, the electronic and band structure were studied. The calculation results show that the binding energy decreases in BixSr1-xTiO3 after Sr2+ replaced by Bi3+. The calculations of the band structure show that BixBa1-xTiO3 are direct band gap semiconductors. The partial substitution of Bi3+ ions can increase the band gap and the absorption spectra ranges shift blue, and the values of band gaps are in the order of Bi0.625Sr0.375TiO3>Bi0.5Sr0.5TiO3>Bi0.25Sr0.75TiO3>SrTiO3>BiTiO3, and the absorption spectrum becomes wider in the order of Bi0.625Sr0.375TiO3>BiTiO3>Bi0.5Sr0.5TiO3>Bi0.25Sr0.75TiO3>SrTiO3. Based on the density of states, the top of the valence band is hybridized by O-2p and Sr-5s and the bottom of the conduction band state is mainly constituted by the Ti-3d state and Bi-6p. The regulation of photo-catalytic activity of the perovskite SrTiO3 can be realized by Bi ions substituting for Sr ions, and Bi-based perovskite BiTiO3 will be a potential photocatalytic material.
关键词： band gap,electronic structure,density of states,absorption spectra,BixSr1-xTiO3
更新于2025-09-10 09:29:36
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Influence of temperature on the oscillations of longitudinal magnetoresistance in semiconductors with a nonparabolic dispersion law
摘要： The density of energy states were obtained in a quantizing magnetic ?eld at different temperature and for nonquadratic dispersion law. The dependence of the density of energy states on temperature in quantizing magnetic ?elds is studied with the nonquadratic dispersion law. The continuous spectrum of the energy density of states at low temperature is transformed into discrete Landau levels. The theory of the temperature dependence of the oscillation Shubnikov–de Haas in semiconductors with a nonparabolic dispersion law is constructed, taking into account the thermal broadening of the Landau levels. The cyclotron effective mass of the electrons is determined from the Shubnikov–de Haas data. The theoretical results are compared with experimental data in Bi1.99Tl0.01Se3.
关键词： Nonparabolic dispersion law,Longitudinal magnetoresistance,Landau levels,Cyclotron effective mass,The density of states,Oscillation Shubnikov–de Haas
更新于2025-09-10 09:29:36