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Crystalline structure, electronic and lattice-dynamics properties of NbTe2
摘要： Layered-structure materials are currently relevant given their quasi-2D nature. Knowledge of their physical properties is currently of major interest. Niobium ditelluride possesses a monoclinic layered-structure with a distortion in the tellurium planes. This structural complexity has hindered the determination of its fundamental physical properties. In this work, NbTe2 crystals were used to elucidate its structural, compositional, electronic and vibrational properties. These findings have been compared with calculations based on density functional theory. The chemical composition and elemental distribution at the nanoscale were obtained through atom probe tomography. Ultraviolet photoelectron spectroscopy allowed the first determination of the work function of NbTe2. Its high value, 5.32 eV, and chemical stability allow foreseeing applications such as contact in optoelectronics. Raman spectra were obtained using different excitation laser lines: 488, 633, and 785 nm. The vibrational frequencies were in agreement with those determined through density functional theory. It was possible to detect a theoretically-predicted, low-frequency, low-intensity Raman active mode not previously observed. The dispersion curves and electronic band structure were calculated, along with their corresponding density of states. The electrical properties, as well as a pseudo-gap in the density of states around the Fermi energy are characteristics proper of a semi metal.
关键词： Electronic band structure,Ultraviolet photoelectron spectroscopy,Density functional theory,Atom probe tomography,Niobium ditelluride,Layered-structure materials,Raman spectra,Density of states,Semimetal
更新于2025-09-23 15:21:01
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The electronic band structure analysis of OLED device by means of in situ LEIPS and UPS combined with GCIB
摘要： Low-energy inverse photoelectron spectroscopy (LEIPS) and ultraviolet photoelectron spectroscopy (UPS) incorporated into the multitechnique XPS system were used to probe the ionization potential and the electron affinity of organic materials, respectively. By utilizing gas cluster ion beam (GCIB), in situ analyses and depth profiling of LEIPS and UPS were also demonstrated. The band structures of the 10-nm-thick buckminsterfullerene (C60) thin film on Au (100 nm)/indium tin oxide (100 nm)/glass substrate were successfully evaluated in depth direction.
关键词： LEIPS–UPS,GCIB depth profile,OLED device,electronic band structure
更新于2025-09-23 15:21:01
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Hybrid functional calculations of electro-optical properties of novel Ga1a??xInxTe ternary chalcogenides
摘要： Doping GaTe semiconductor with indium can be beneficial in the realization of high-quality radiation detectors. In this study, first-principle calculations based on the density functional theory have been used to investigate the structural and electro-optical properties of Ga1?xInxTe alloys. For the electronic structure calculations, the exchange–correlation functionals are treated with an accurate PBE0 hybrid functional giving improved agreement with experimental band energies. The influence of the In concentration on the energy band gaps is analyzed. Furthermore, the direction for the highest mobility of Ga1?xInxTe is estimated by calculating the effective mass of carriers respecting to the crystallographic directions from calculated electronic band structures. Optical spectra of Ga1?xInxTe are evaluated for all compositions (x = 0, 0.25, 0.5 and 0.75) and for different polarization directions in the range of 0–14 eV. The calculated optical spectra of Ga1–xInxTe are found to have a remarkable redshift as the alloying composition increases. The calculated static dielectric constant for the entire concentration shows that the considered alloys are a high-dielectric constant materials. Our study shows that Ga1?xInxTe alloys exhibit metallic properties in some energy ranges. Our results suggest that the new Ga1?xInxTe alloys are a promising material for radiation detectors, microelectronics and optoelectronic devices.
关键词： First-principles calculations,Band structure,Effective mass,Ga1–xinxte,Dielectric function,PBE0 hybrid functional
更新于2025-09-23 15:21:01
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Energy band and transport properties in magnetic aperiodic graphene superlattices of Thue-Morse sequence
摘要： Utilizing the transfer matrix method, we develop the electronic band structure and transport properties in Thue-Morse aperiodic graphene superlattices with magnetic barriers. It is found that the normal transmission is blocked and the position of the Dirac point can be shifted along the wavevector axis by changing the height and width ratio of magnetic barriers, which is intrinsic di?erent from electronic ?eld modulated superlattices. In addition, the angular threshold property of the transmission spectra and the oscillatory property of the conductance have been studied.
关键词： graphene superlattices,transport properties,electronic band structure,magnetic barriers,Thue-Morse sequence
更新于2025-09-23 15:21:01
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Investigation of the structural and electronic properties of InP1-xSbx alloy for mid-infrared optoelectronic applications: A TB-mBJ DFT study
摘要： The structural and electronic properties of InP1(cid:1)xSbx supercell structure at different percent of Sb incorporation have been studied under the Density Functional Theory formalism employing WIEN2K package. From the total energy calculations, the supercell lattice structures have been optimized. The structural properties have been calculated from the equation of state which suggests the supercell structures to be signi?cantly stable with a higher degree of compressive ?exibility (speci?cally, at lower percent of Sb incorporation). The contribution of the partial and total DOS (Density of States) of constituent elements to total DOS of the supercell structure has been investigated. The relativistic effects have been assimilated into the band structure calculation, along various high symmetry k directions for each supercell structure. The values obtained for band gap (both, direct and indirect), spin-orbit splitting energy and bowing coef?cient have been observed to vary signi?cantly as a function of Sb mole fraction. Moreover, a relationship has been established between band gap (both, direct and indirect) values and spin-orbit splitting energy with Sb mole fraction. The in?uence of SOC (spin-orbit coupling) effect on the parameters concerning electronic properties has also been analyzed. The effective mass values for conduction and valence sub-bands (heavy hole, light hole and spin orbit split-off hole) near the Brillouin zone has been calculated at different percent of Sb incorporation in InP1(cid:1)xSbx supercell structure. The interpretation of these results obtained suggests InP1(cid:1)xSbx material to be competent for mid-infrared optoelectronic applications.
关键词： III-V semiconductor,Electronic band structure,DOS,DFT calculation,Effective mass calculation,Structural and electronic property
更新于2025-09-23 15:21:01
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van der Waals epitaxial growth of single crystal α-MoO3 layers on layered materials growth templates
摘要： Monolayer and multilayer α-MoO3 nanosheets are successfully grown on a 2D substrate by simply evaporating amorphous molybdenum oxide thin film in ambient conditions. A single-crystal α-MoO3 nanosheet without grain boundary is epitaxially grown on various 2D substrates despite a large lattice mismatch. During growth, the quasi-stable monolayer α-MoO3 first covers the 2D substrate, then additional layers are continuously grown on the first monolayer α-MoO3. The band gap of the α-MoO3 increases from 2.9 to 3.2 eV as the thickness decreases. Furthermore, due to oxygen vacancies and surface adsorbates, the synthesized α-MoO3 is highly n-doped with a small work function. Therefore, α-MoO3 field-effect transistors (FETs) exhibit a typical n-type conductance. This work shows the great potential of ultra-thin α-MoO3 in 2D-material-based electronics.
关键词： work function,van der Waals epitaxy,band structure,vacancy,transition metal oxide,stability,2D materials,lattice mismatch,transistor,heterostructure
更新于2025-09-23 15:21:01
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Study the electronic properties and magnetization of rutile polymorph CoxTi1-xO2 super cell at various cobalt (Co) concentrations using first principle calculation
摘要： First principle calculation has been performed to study the electronic properties and magnetization of CoxTi1-xO2 at different cobalt concentration. Equilibrium lattice constant of CoxTi1-xO2 at 0.0% cobalt concentration was obtained about 4.81?. The obtained value is slightly larger than the experimental value. The calculated band gap of CoxTi1-xO2 at 0.0% cobalt concentration is 3.0 eV which consistent with other reports. The calculated band gap for 16.6% is 0.5 eV, for 33.3% is 0.1 eV and for 50.0% is approximately 0.0 eV. The calculated band gap of CoxTi1-xO2 decreased with increased cobalt concentration. On the other hand at 0.0% cobalt concentration, the magnetization is zero and at 50.0% cobalt concentration, magnetization is 3.36 Bohr mag/cell. The density of states calculation for spins up and spins down are symmetric at 16.6% and 33.3% cobalt concentration. At 50.0% cobalt concentration the density of states shows asymmetric for spin up and spin down which indicates the ferromagnetic nature.
关键词： Band structure,Magnetization,Equilibrium lattice constant,Density function theory (DFT),Density of State (DOS)
更新于2025-09-23 15:21:01
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Compton spectroscopy and electronic structure study for tetragonal barium titanate
摘要： The Compton profile of tetragonal BaTiO3 is measured using 20 Ci 137Cs Compton spectrometer. The experimental data have been analyzed using theoretical electron momentum densities computed using linear combination of atomic orbitals (LCAO) with density functional theory (DFT) and the hybridization of Hartree-Fock and DFT (WC1LYP scheme). It observed that hybrid scheme WC1LYP provides a better agreement with the experimental data than other approximations of exchange-correlation (with generalized gradient approximation like PBESol, SOGGA and local density approximation like LDAPZ) as considered in the present work. In addition, the energy bands and density of states have been reported using LCAO-WC1LYP scheme. The WC1LYP hybrid method confirms wide band gap semiconducting nature of tetragonal BaTiO3. Further, a relative nature of bonding among CaTiO3, SrTiO3 and BaTiO3 has also been discussed using equal-valence-electron-density profiles and Mulliken’s population analysis which predict a trend of increasing iconicity in the order CaTiO3→BaTiO3→SrTiO3.
关键词： Band structure calculations,X-ray scattering,Density functional theory,Titanate
更新于2025-09-19 17:15:36
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Theoretical Study on the Charge Transport Property of Thia- or Selenadiazole Compound
摘要： In this work, we carried out theoretical investigation on the charge-transporting nature of 4,11-bis-[(triisopropylsilanyl)-ethynyl]-2-thia-1,3-diaza-cyclopenta[b]anthracene (1) and 4,11-bis-[(triisopropylsilanyl)-ethynyl]-2-selena-1,3-diaza-cyclopenta[b]anthracene (2) by Marcus theory and first-principle band structure. The character of the frontier molecular orbitals, reorganization energies, transfer integrals and band structures are considered in detail. The results show that the compounds 1 and 2 are ambipolar material, both electron and hole are favor of transporting. The intermolecular π-π ineraction and S···N/Se···N interaction provide the holes and electrons transport channels. The introduction of Se atom can effectively reduce the reorganization energy and considerably improve the electron transfer integrals, thus 2 is found to be a good candidate for ambipolar semiconducting material with high mobility and balanced transport.
关键词： DFT,Marcus theory,Band structure
更新于2025-09-19 17:15:36
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A multiscale materials-to-systems modeling of polycrystalline PbSe photodetectors
摘要： We present a physics based multiscale materials-to-systems model for polycrystalline PbSe photodetectors that connects fundamental material properties to circuit level performance metrics. From experimentally observed ?lm structures and electrical characterization, we ?rst develop a band structure model that explains carrier-type inversion and large carrier lifetimes in sensitized ?lms. The unique band structure of the photosensitive ?lm causes separation of generated carriers with holes migrating to the inverted PbSejPbI2 interface, while electrons are trapped in the bulk of the ?lm intergrain regions. These ?ows together form the 2-current theory of photoconduction that quantitatively captures the I(cid:2)V relationship in these ?lms. To capture the e?ect of pixel scaling and trapped carrier blocking, we develop a model for the metallic contacts with the detector ?lms based on the relative workfunction di?erences. We also develop detailed models for various physical parameters such as mobility, lifetime, quantum e?ciency, noise, etc. that connect the detector performance metrics such as responsivity R and speci?c detectivity D* intimately with material properties and operating conditions. A compact Verilog-A based SPICE model is developed which can be directly combined with advanced digital Read-Out Integrated Circuit cell designs to simulate and optimize high performance Focal Plane Arrays which form a critical component in the rapidly expanding market of self-driven automotive, internet of things security, and embedded applications.
关键词： polycrystalline materials,PbSe photodetectors,carrier-type inversion,multiscale modeling,quantum efficiency,band structure,SPICE model
更新于2025-09-19 17:13:59