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Effect of confinement potential shape on the electronic, thermodynamic, magnetic and transport properties of a GaAs quantum dot at finite temperature
摘要： The effect of the shape of the confinement potential on the electronic, thermodynamic, magnetic and transport properties of a GaAs quantum dot is studied using the power-exponential potential model with steepness parameter p. The average energy, heat capacity, magnetic susceptibility and persistent current are calculated using the canonical ensemble approach at low temperature. It is shown that for soft confinement, the average energy depends strongly on p while it is almost independent of p for hard confinement. The heat capacity is found to be independent of the shape and depth of the confinement potential at low temperatures and for the magnetic field considered. It is shown that the system undergoes a paramagnetic-diamagnetic transition at a critical value of the magnetic field. It is furthermore shown that for low values of the potential depth, the system is always diamagnetic irrespective of the shape of the potential if the magnetic field exceeds a certain value. For a range of the magnetic field, there exists a window of p values in which a re-entrant behavior into the diamagnetic phase can occur. Finally, it is shown that the persistent current in the present quantum dot is diamagnetic in nature and its magnitude increases with the depth of the dot potential but is independent of p for the parameters considered.
关键词： transport properties,thermodynamic properties,canonical ensemble approach,electronic properties,quantum dot,GaAs,paramagnetic-diamagnetic transition,persistent current,magnetic properties,power-exponential potential model,confinement potential
更新于2025-09-11 14:15:04
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Characterization of the Electronic Properties of Single‐Walled Carbon Nanotubes Filled with an Electron Donor—Rubidium Iodide: Multifrequency Raman and X‐ray Photoelectron Spectroscopy Studies
摘要： Single-walled carbon nanotubes (SWCNTs) with a mean diameter of 1.4 nm are filled with rubidium iodide. The filling of nanotubes is proved by high-resolution scanning transmission electron microscopy. The chemical composition of the filler is confirmed by X-ray photoelectron spectroscopy (XPS). The electronic properties of the filled SWCNTs are studied by XPS and Raman spectroscopy. The encapsulated salt leads to n-doping of nanotubes. The detailed multifrequency Raman spectroscopy investigation of the alteration of Raman modes of SWCNTs upon filling is conducted. The doping-induced changes in the radial breathing mode and G-band are revealed. It is found that these changes differ for the metallic and semiconducting SWCNTs. The obtained data and revealed trends are expected to be helpful for forthcoming studies to interpret the observed changes in Raman spectra of filled metallic and semiconducting SWCNTs.
关键词： Raman spectroscopy,electronic properties,X-ray photoelectron spectroscopy,rubidium iodide,filling,single-walled carbon nanotubes
更新于2025-09-11 14:15:04
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Reference Module in Materials Science and Materials Engineering || Excitonic Model versus Band Gap Model in Organic Materials
摘要： The binding energy Eb of an optical excitation is a key parameter for the understanding of the opto-electronic properties of organic solids in general and of conjugated polymers in particular. It controls the dissociation of an electronic excitation of either singlet or triplet character into a pair of free charges as well as the reverse process, i.e., the recombination of an electron–hole (eh) pair yielding an excitation that can decay radiatively or nonradiatively. If Eb is large, photogeneration of charge carriers is an endothermic, inefficient process. It is obvious that in an organic solar cell (OSC) one would like Eb to be as small as possible, while in a light emitting diode (LED) it is the opposite because charge recombination requires a driving force. In this article an outline of the problem of defining the exciton binding in a molecular solid will be presented followed by experimental and theoretical advances and a critical review of relevant conceptual frameworks with particular emphasis on conjugated polymers.
关键词： Organic Materials,Conjugated Polymers,Band Gap Model,Opto-electronic Properties,Exciton Binding Energy
更新于2025-09-11 14:15:04
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Computational Chemistry Meets Experiments for Explaining the Geometry, Electronic Structure, and Optical Properties of Ca <sub/>10</sub> V <sub/>6</sub> O <sub/>25</sub>
摘要： In this paper, we present a combined experimental and theoretical study to disclose, for the first time, the structural, electronic, and optical properties of Ca10V6O25 crystals. The microwave-assisted hydrothermal (MAH) method has been employed to synthesize these crystals with different morphologies, within a short reaction time at 120 °C. First-principle quantum mechanical calculations have been performed at the density functional theory level to obtain the geometry and electronic properties of Ca10V6O25 crystal in the fundamental and excited electronic states (singlet and triplet). These results, combined with the measurements of X-ray diffraction (XRD) and Rietveld refinements, confirm that the building blocks lattice of the Ca10V6O25 crystals consist of three types of distorted 6-fold coordination [CaO6] clusters: octahedral, prism and pentagonal pyramidal, and distorted tetrahedral [VO4] clusters. Theoretical and experimental results on the structure and vibrational frequencies are in agreement. Thus, it was possible to assign the Raman modes for the Ca10V6O25 superstructure, which will allow us to show the structure of the unit cell of the material, as well as the coordination of the Ca and V atoms. This also allowed us to understand the charge transfer process that happens in the singlet state (s) and the excited states, singlet (s*) and triplet (t*), generating the photoluminescence emissions of the Ca10V6O25 crystals.
关键词： structural properties,electronic properties,Ca10V6O25,microwave-assisted hydrothermal method,photoluminescence,optical properties
更新于2025-09-10 09:29:36
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Strain engineering of electronic, elastic, and piezoelectric responses in oxygen-decorated phosphorene
摘要： The electronic, elastic, and piezoelectric properties of semi-oxidized phosphorene subjected to uniaxial strains were studied using first-principles calculations based on the density functional theory. Both zigzag and armchair uniaxial loads caused significant changes in partial charges and band gaps as a semiconductor–metal transition occurs outside the metastable regions. The bridge structures exhibited great flexibility along the armchair direction resulting from the high buckling parameter in these structures. The calculations confirmed the linear response of polarization. The in plane and out of plane stress piezoelectric coefficients were comparable to 2D materials. The results demonstrated that both the uniaxial strain and the oxygen atom arrangement can be used to tune the anisotropic properties of phosphorene making the new derivatives ideal for flexible devices and energy conversion applications.
关键词： Phosphorene oxides,electronic properties,piezoelectric response,elastic regions,strain effect
更新于2025-09-10 09:29:36
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Impact of Precise Control over Microstructure in Thiophene–Selenophene Copolymers
摘要： Controlling the sequence of repeat units in a synthetic polymer has been a long-standing topic of interest in chemistry. As methods to regulate sequence become more sophisticated, it is critical to consider how controlling the arrangement of repeat units along the polymer backbone impacts properties. In this work, thiophene?selenophene copolymers (statistical and periodic) were compared to elucidate the impact of periodicity on electronic properties and structural organization in conjugated macromolecules. Polymers were synthesized using catalyst-transfer polycondensation (CTP) enabling control over molecular weight and dispersity. The study revealed that optical bandgaps and redox potentials of periodic and statistical copolymers varied with composition in a predictable manner, regardless of monomer ordering along the chain. While the bandgaps of the two types of copolymers were indistinguishable, X-ray scattering revealed di?erences in solid-state packing. Both types of copolymers exhibited well-de?ned morphologies, but larger π-stacking distances and more orientational disorder were evident in the statistical systems. This indicates periodicity is an attribute that should be considered when synthesizing semiconducting materials.
关键词： solid-state packing,periodicity,electronic properties,thiophene?selenophene copolymers,catalyst-transfer polycondensation
更新于2025-09-10 09:29:36
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Impacts of in-plane strain on commensurate graphene/hexagonal boron nitride superlattices
摘要： Due to atomically thin structure, graphene/hexagonal boron nitride (G/hBN) heterostructures are intensively sensitive to the external mechanical forces and deformations being applied to their lattice structure. In particular, strain can lead to the modification of the electronic properties of G/hBN. Furthermore, moiré structures driven by misalignment of graphene and hBN layers introduce new features to the electronic behavior of G/hBN. Utilizing ab initio calculation, we study the strain-induced modification of the electronic properties of diverse stacking faults of G/hBN when applying in-plane strain on both layers, simultaneously. We observe that the interplay of few percent magnitude in-plane strain and moiré pattern in the experimentally applicable systems leads to considerable valley drifts, band gap modulation and enhancement of the substrate-induced Fermi velocity renormalization. Furthermore, we find that regardless of the strain alignment, the zigzag direction becomes more efficient for electronic transport, when applying in-plane non-equibiaxial strains.
关键词： strain,graphene/hexagonal boron nitride,moiré pattern,electronic properties
更新于2025-09-10 09:29:36
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Electronic properties of Zigzag ZnO nanoribbons with Hydrogen and Magnesium passivations
摘要： In this study, the electronic properties of ZnO nanoribbons with zigzag edges (ZZnONr) have been investigated with Density Functional Theory (DFT). After a geometric optimization, the electronic band structures, the density of states (DOS) of ZZnONr passivated with Hydrogen (H) and Magnesium (Mg) atoms were calculated ZZnONr. It is shown that the increasing width of ZZnONrs has led to a decrement in energy band gap of the studied structures. While ZZnONr passivated with Mg for Zn-rich edge have not been shown a spin dependency, the structure passivated with Mg for O-rich edge have exhibited spin-dependent band structure. The energetically most stable structures have been determined as ZZnONr passivated with Mg for Zn-rich edge. ZZnONr passivated with Mg atoms for both edges have a graphene-like band structure especially for 8 and 10 atom width structures and this property of ZZnONrs could be important in terms of the electron transport for ZZnONrs.
关键词： ZnONr,Passivation,electronic properties,DFT
更新于2025-09-10 09:29:36
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[Chemical Modelling] Chemical Modelling Volume 14 (Volume 14) || From graphene to borophene the fascinating 2D materials
摘要： In nature, a free-standing single-atom sheet of any chemical element does not exist and nobody could imagine the existence of such structure. However, scientists succeeded to synthesis single-atom sheets of boron or carbon sheets and to investigate their properties. Therefore, single-Layer sheets are nowadays of highly interesting 2D materials, due to their unique electronic, mechanical, optical and magnetic properties, and their potential applications in nanotechnology.
关键词： borophene,nanotechnology,graphene,2D materials,electronic properties
更新于2025-09-10 09:29:36
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Effects of Electron-Phonon Coupling on Electronic Properties of Methylammonium Lead Iodide Perovskites
摘要： Temperature can have a dramatic effect on the solar efficiency of methylammonium lead iodide (CH3NH3PbI3) absorbers due to changes in the electronic structure of the system even within the range of stability of a single phase. Herein using first principles density functional theory, we investigate the electron band structure of the tetragonal and orthorhombic phases of CH3NH3PbI3 as a function of temperature. The electron-phonon interactions are computed to all orders using a Monte Carlo approach, which is needed considering that the second-order Allen-Heine-Cardona theory in electron-phonon coupling is not adequate. Our results show that the band gap increases with temperature in excellent agreement with experimental results. We verified that anharmonic effects are only important near the tetragonal-cubic phase transition temperature. We also found that temperature has a significant effect on the effective masses and Rashba coupling. At room temperature, electron–phonon coupling is found to enhance the band effective mass by a factor of two, and to diminish the Rashba coupling by the same factor compared to T=0 K values. Our results underscore the significant impact of electron-phonon coupling on electronic properties of the hybrid perovskites.
关键词： Energy Conversion and Storage,Methylammonium Lead Iodide Perovskites,Plasmonics and Optoelectronics,Electron-Phonon Coupling,Electronic Properties
更新于2025-09-10 09:29:36