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Hydrogenation and Fluorination of 2D Boron Phosphide and Boron Arsenide: A Density Functional Theory Investigation
摘要： First-principles density functional theory calculations are performed to study the stability and electronic properties of hydrogenated and fluorinated two-dimensional sp3 boron phosphide (BP) and boron arsenide (BAs). As expected, the phonon dispersion spectrum and phonon density of states of hydrogenated and fluorinated BX (X = P, As) systems are found to be different, which can be attributed to the different masses of hydrogen and fluorine. Hydrogenated BX systems bear larger and indirect band gaps and are found to be different from fluorinated BX systems. These derivatives can be utilized in hydrogen storage applications and ultrafast electronic devices. Finally, we investigated the stability and electronic properties of stacked bilayers of functionalized BP. Interestingly, we found that these systems display strong interlayer interactions, which impart strong stability. In contrast with the electronic properties determined for the fluorinated/hydrogenated monolayers, we found that the electronic properties of these bilayers can finely be tuned to a narrow gap semiconductor, metallic or nearly semimetallic one by selecting a suitable arrangement of layers. Moreover, the nearly linear dispersion of the conduction band edge and the heavy-, light-hole bands are the interesting characteristics. Furthermore, the exceptional values of effective masses assure the fast electronic transport, making this material very attractive to construct electronic devices.
关键词： boron phosphide,boron arsenide,hydrogenation,fluorination,density functional theory,electronic properties,stability
更新于2025-09-10 09:29:36
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First-principles study of elastic, electronic, optical and thermoelectric properties of newly synthesized K2Cu2GeS4 chalcogenide
摘要： In this article, we report the elastic, electronic, optical and thermoelectric properties of recently synthesized K2Cu2GeS4 chalcogenide. The structural parameters are found to be in good agreement with experimental results. The calculated single crystal elastic constants (Cij) show that K2Cu2GeS4 is mechanically stable. The investigated electronic band structures reveal semiconducting characteristics and are consistent with experiment. Important optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function are calculated and discussed in detail. Optical conductivity is found to be in good qualitative agreement with the results of band structure calculations. The Seebeck coefficients for TB-mBJ potential within the studied temperature range vary from ~450 to ~200 m V/K. The anisotropic electrical conductivity and electronic thermal conductivity are observed in the layered structured K2Cu2GeS4. The power factor and electronic thermal conductivity at 800K along xx-axis using TB-mBJ potential are found to be ~6 m Wcm-1K-2 and 0.578 Wm-1K-1, respectively and the corresponding thermoelectric figure of merit is 0.81. The obtained results predict that K2Cu2GeS4 is a promising material in thermoelectric device applications.
关键词： electronic properties,optical properties,elastic properties,thermoelectric properties,K2Cu2GeS4
更新于2025-09-09 09:28:46
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Organic–Organic Heterostructures
摘要： Thin films of organic molecules are now of technological importance as the active component in modern electronic and optoelectronic devices, such as organic light-emitting devices, organic thin-film transistors, organic sensors, and organic photovoltaic devices. After a first era of general excitement, it was soon discovered that to be able to rival their inorganic counterparts, one has to control the structure, crystallinity, and morphology during thin-film growth and understand and control their molecular electronic properties. An important topic therein is the formation of interfaces, specifically the organic-metal interface, which acts as the contact. Consequently, the growth and the electronic level alignment (band alignment) of organic molecules on metal surfaces have been extensively studied for the last 20 years. However, organic devices in general comprise more than one organic layer. As a consequence, we also have to consider organic–organic interfaces and the electronic level alignment across them and how heteroorganic films form. In comparison with the huge number of publications dealing with organic film growth on metal, the literature of controlled surface science studies of organic film growth on an organic layer is rather scarce. And indeed, there are a number of challenges one has to be aware of, when investigating organic heterostructure formation. In contrast to metal single-crystal substrates, which are available in every orientation, organic single crystals, large enough to handle with surface science methods, are hardly available, let alone in various orientations. The best approximation to a single crystal is organic thin films composed of crystallites of the same orientation that tile the substrate surface. By careful selection of the inorganic substrate and growth conditions, a number of orientations can be achieved. A second difficulty is that many surface science methods use electrons and thus can be prone to charging and beam damage particular for thick films.
关键词： electronic devices,optoelectronic devices,thin films,organic-metal interface,Organic–organic heterostructures,molecular electronic properties
更新于2025-09-09 09:28:46
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Growth, Morphology and Stability of Au in Contact with the Bi2Se3(0001) Surface
摘要： We report a combined microscopy and spectroscopy study of Au deposited on the Bi2Se3(0001) single crystal surface. At room temperature Au forms islands, according to the Volmer–Weber growth mode. Upon annealing to 100° C the Au deposits are not stable and assemble into larger and thicker islands. The topological surface state of Bi2Se3 is weakly affected by the presence of Au. Contrary to other metals, such as Ag or Cr, a strong chemical instability at the Au/Bi2Se3 interface is ruled out. Core level analysis highlights Bi diffusion toward the surface of Au islands, in agreement with previous findings, while chemical interaction between Au and atomic Se is limited at the interfacial region. For the investigated range of Au coverages, the Au/Bi2Se3 heterostructure is inert towards CO and CO2 exposure at low pressure (10-8 mbar) regime.
关键词： metal to topological insulator contact,chemical properties,photoemission spectroscopy,growth mode,electronic properties,microscopy
更新于2025-09-09 09:28:46
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Semiconducting Polymer Spherulites-From Fundamentals to Polymer Electronics
摘要： The control of the morphology of semiconducting semicrystalline polymers is crucial to the performance of various electronic devices. Among other superstructures in semicrystalline polymers, spherulites stand out for various reasons. They are highly ordered, relatively easy to grow, and their underlying molecular structure provides anisotropic optical and electronic properties of the resulting polymeric material. In this feature article, a short overview of classical crystallization theory is given as well as a brief introduction to spherulites as supermolecular structures. The article then focuses on semicrystalline polymers with semiconducting properties. From classical melt crystallization toward solvent vapor annealing, different strategies of growing spherulites of these types of polymers are presented and examples of the corresponding polymers and their resulting morphology are given. Eventually, the potential application of spherulitic thin films in organic electronics such as field-effect transistors is demonstrated. Conductivity and mobility measurements are shown, particularly focusing on the anisotropy of the latter.
关键词： optical properties,spherulites,conducting polymers,crystallization,electronic properties
更新于2025-09-09 09:28:46
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Size and strain effects on mechanical and electronic properties of green phosphorene nanoribbons
摘要： Recently, a phosphorus isomer named green phosphorus was theoretically predicted with a similar interlayer interaction compared to that of black phosphorus, thus indicating that individual layers can be mechanically exfoliated to form two-dimensional (2D) layers known as green phosphorene. In this work, we investigated the properties of green phosphorene nanoribbons along both armchair and zigzag directions with ribbon widths up to 57 ? using density functional theory. Effects of ribbon width and strain on the mechanical and electronic properties of the ribbons were studied. The Young’s modulus, effect of quantum con?nement on the band gap, and effect of strain on the band structures of the ribbons were investigated. The green phosphorene ribbons were found to exhibit prominent anisotropic properties, with the Young’s modulus in the range of 10-35 GPa for the armchair green phosphorene nanoribbons (AGPNR) and 160-170 GPa for the zigzag green phosphorene nanoribbons (ZGPNR), which are the same order of magnitude as those of the 2D sheets. The work function was found to be between 5 eV ～ 5.7 eV for the range of widths studied. Both size and strain trigger direct-indirect band gap transitions in the ribbons and their transition mechanisms were discussed.
关键词： green phosphorene,mechanical properties,nanoribbons,electronic properties,density functional theory
更新于2025-09-09 09:28:46
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Geometry-diversified Coulomb excitations in trilayer AAB stacking graphene
摘要： The lower-symmetry trilayer AAB-stacked graphene exhibits rich electronic properties and diverse Coulomb excitations. Three pairs of unusual valence and conduction bands create nine available interband excitations for the undoped case, in which the imaginary (real) part of the polarizability shows one-dimensional square root asymmetric peaks and two-dimensional shoulder structures (pairs of antisymmetric peaks and logarithm-type symmetric peaks). The low-frequency acoustic plasmon, being revealed as a prominent peak in the energy-loss spectrum, can survive in a narrow-gap system with the large density of states from the valence band. This type of plasmon mode is similar to that in a narrow-gap carbon nanotube. However, the decisive mechanism governing this plasmon is the intraband conduction state excitations. Its frequency, intensity and critical momentum exhibit a nonmonotonic dependence on the Fermi energy. The well-de?ned electron-hole excitation boundaries and the higher frequency optical plasmons are transformed by varying the Fermi energy. Many substantial differences between the electronic properties of AAB and other trilayer graphene stackings are discussed.
关键词： Coulomb excitations,Fermi energy,electronic properties,plasmon modes,trilayer AAB-stacked graphene
更新于2025-09-09 09:28:46
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Highly Promoted Carrier Mobility and Intrinsic Stability by Rolling Up Monolayer Black Phosphorus into Nanoscrolls
摘要： Rolling up two-dimensional (2D) materials into nanoscrolls could not only retain the excellent properties of their 2D hosts, but also display intriguing physical and chemical properties that arise from their 1D tubular structures. Here, we report a new class of black phosphorus nanoscrolls (bPNSs), which are stable at room-temperature and energetically more favorable than 2D bP. Most strikingly, these bPNSs hold tunable direct band gaps and extremely high mobilities (e.g., the mobility of the double-layer bPNS is about 20-fold higher than that of 2D bP monolayer). Their unique self-encapsulation structure and layer-dependent conduction band minimum can largely prevent the entering of O2 and the production of O?2 and thereby suppress the possible environmental degradation as well. The enhanced intrinsic stability and promoted electronic properties render bPNSs great promise in many advanced electronics or optoelectronics applications.
关键词： optoelectronic applications,black phosphorus nanoscrolls,carrier mobility,intrinsic stability,electronic properties
更新于2025-09-09 09:28:46
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Polarization-Direction Dependence of Thermodynamic Stability of Ferroelectric BiAlO <sub/>3</sub> (0001) Polar Surfaces
摘要： Polar surfaces of ferroelectric oxides are of great importance for both fundamental and practical interest. In this report, we present a theoretical study to determine the thermodynamic stability and electronic properties of ferroelectric BiAlO3(0001) surfaces. According to the calculated surface phase diagram, we predict that the equilibrium stoichiometries are distinct for the oppositely polarized BiAlO3 surfaces under the same chemical conditions. In addition to nonstoichiometry of the surface chemical compositions, we find that anomalous filling of the surface states can also result in surface metallization in order to compensate the remarkable surface polarity. Besides providing atomic-scale understanding of the BiAlO3(0001) surfaces, we also put forward the practical implications in novel magnetoelectric devices and advanced surface chemistry.
关键词： Magnetoelectric devices,Surface chemistry,Thermodynamic stability,Surface metallization,BiAlO3(0001) surfaces,Electronic properties,Ferroelectric oxides
更新于2025-09-09 09:28:46
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Mechanical, Electronic and Optical Properties of Two Phases of NbB4: First-Principles Calculations
摘要： As transition metal borides have been successfully synthesised, the study of the combination of transition metal and boron is another effective way to investigate the properties of boride. We have predicted the novel phase Amm2-NbB4. Using the Cambridge Serial Total Energy Package (CASTEP) code, we further researched on the mechanical, electronic and optical properties of C2/c- and Amm2-NbB4. It is found that both the phases of NbB4 are dynamically and mechanically stable at 0 and 100 GPa. Their Vickers hardness values are both 34 GPa, which indicate that they are hard materials. The band gap of C2/c-NbB4 is 0.145 eV, which indicates that it is a semiconductor (or metalloid) at 0 GPa. For the Amm2-NbB4, the band structure without band gap indicates it is a metal at 0 GPa. The optical properties of these two structures are similar. At 0 eV, the real part of dielectric function is 28.8 for C2/c-NbB4, and the real part value for Amm2-NbB4 is 43. We hope our work will provide some help to the experimental work about the technology of the material.
关键词： Mechanical Properties,Optical Properties,First-Principles Calculations,Electronic Properties,NbB4
更新于2025-09-04 15:30:14