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Computational Study on Interfaces and Interface Defects of Amorphous Silica and Silicon
摘要： The amorphous SiO2/Si interface is arguably the most important part in semiconductor technology, strongly influencing the device reliability. Its electronic structure is affected by the defects, majorly the dangling bonds known as Pb-type defects, which have been studied for decades. These defects are usually passivated by hydrogen atoms in device processing, which eliminates the defect levels in the silicon bandgap and thus removes their electric activity. However, when the interface is exposed to ionization radiation, the passivated defects can be reactivated by the protons generated by radiation, which significantly affects the device performance and causes reliability issues. In this review, computational studies on the amorphous SiO2/Si interface and interface defects are summarized, including the modeling of the interface, the main interface defects, and their depassivation, and compared to experimental results. The hyperfine parameters are emphasized, because they are essential to identify the structures of the interface defects. The defect levels and depassivation of the defects are also emphasized, because the former directly affect the device performance and the latter directly generates the dangling bonds in the interface.
关键词： depassivation,ionizing damage,interface defects,amorphous interfaces,first-principles calculations
更新于2025-09-23 15:23:52
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Valley and spin splitting in monolayer TX2/antiferromagnetic MnO (T=Mo, W; X=S, Se) van der Waals heterostructures
摘要： The electronic structure of monolayer MoS2, WS2, MoSe2 and WSe2 on top of antiferromagnetic MnO(111) is investigated systematically by first-principles calculations. It is found that the time-reversal symmetry is broken by the stacking on MnO that leads to the valley polarization. The valley splitting of MoS2/MnO, WS2/MnO, MoSe2/MnO and WSe2/MnO is 161, 193, 171 and 125 meV for K point, and 18 to 253 meV for K' point. The pattern of stacking also induces p- or n-type doping of MoS2, revealing that the conductivity of the heterostructues could be tuned by stacking on MnO. Besides, we also calculate electronic structures of WS2/MnO, MoSe2/MnO and WSe2/MnO heterostructures in the configuration of Mn-terminated (III), and find the spin splitting at K point is 553, 324 and 481 meV, and 215, 9 and 284 meV for K' point, respectively. Furthermore, the termination of MnO substrate can switch the spin splitting of monolayer MoS2, WS2, MoSe2 and WSe2. The spin splitting of MoS2/MnO for six possible interface configurations is varied from 24 to 291 meV for K point, and 18 to 253 meV for K' point. The results present a new type of novel heterostructure that has potential applications in the spintronic and valleytronic devices.
关键词： Two dimensional materials,Heterostructure,Transition metal dichalcogenides,First-principles calculations
更新于2025-09-23 15:23:52
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Enhanced stability and optical absorption in the perovskite‐based compounds MA$_{1‐x}$Cs$_x$PbI$_{3‐y}$Br$_y$
摘要： Organometal halide perovskites have been outstanding from enormous amount of functional materials thanks to their highly cost-effective processability and prominent light harvesting capacity. Unfortunately, poor long-term stability seriously hinders their further development. The recent experimental observations suggest that Cesium is a promising candidate to enhance the stability of MAPbI3. To explore the inherent mechanism, a first-principles investigation based on density functional theory, including hybrid functional, has been performed to analyze the electronic and optical properties of perovskite series MA0.75Cs0.25PbI3-yBry. The results indicate that perovskite compound MA0.75Cs0.25PbI2Br is significantly superior to the other doped series in terms of optical absorption within the visible-light range. In the meanwhile, both Bader charge analysis and charge density distribution show that the compound of MA0.75Cs0.25PbI2Br is the most stable among all the doped perovskite series. Moreover, it is clearly manifested that the impact of cesium is mainly embodied in the enhancement of the stability rather than in the improvement of optical absorption. Our study sheds a new light on screening new-type light harvesting materials, and provides theoretical insight into the rationale design of highly efficient and stable photovoltaic devices based on these functional materials.
关键词： optical absorption,stability,first-principles calculations,perovskite compounds
更新于2025-09-23 15:23:52
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Interface properties of nonpolar LiAlO2/SrTiO3 heterostructures
摘要： Advances in creating metal oxide heterostructures have received a great deal of attention because novel properties like two-dimensional electron gas (2DEG), which was first found in LaAlO3/SrTiO3 interface, while does not exist in the bulk materials. To extend the study on 2DEG, we investigate the electronic property of interesting nonpolar/nonpolar LiAlO2/SrTiO3 heterostructure (also perovskite/nonperovskite oxide heterostructure), with and without oxygen vacancies by first-principles calculations. Two types of interfaces, SrO/LiAlO2 and TiO2/LiAlO2 interfaces, were modeled with the stable stacking configurations. Oxygen vacancies at LiAlO2/SrTiO3 interface induce the carriers in this system. there is no 2DEG behavior detected. Our results show that three-dimensional transport behavior occurs in the perovskite/non-perovskite oxide interface.
关键词： Metal oxide heterostructures,First-principles calculations,Oxygen vacancies,LiAlO2,SrTiO3
更新于2025-09-23 15:23:52
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Using First-Principles Calculations in CALPHAD Models to Determine Carrier Concentration of the Binary PbSe Semiconductor
摘要： PbSe is a promising thermoelectric that can be further improved by nanostructuring, band engineering, and carrier concentration tuning; therefore, a firm understanding of the defects in PbSe is necessary. The formation energies of point defects in PbSe are computed via first-principles calculations under the dilute-limit approximation. We find that under Pb-rich conditions, PbSe is an n-type semiconductor dominated by doubly-charged Se vacancies. Conversely, under Se-rich conditions, PbSe is a p-type semiconductor dominated by doubly-charged Pb vacancies. Both of these results agree with previously performed experiments. Temperature- and chemical potential-dependent Fermi levels and carrier concentrations are found by enforcing the condition of charge neutrality across all charged atomic and electronic states in the system. The first-principles-predicted charge-carrier concentration is in qualitative agreement with experiment, but slightly varies in the magnitude of carriers. To better describe the experimental data, a CALPHAD assessment of PbSe is performed. Parameters determined via first-principles calculations are used as inputs to a five-sublattice CALPHAD model that was developed explicitly for binary semiconductors. This five sublattice model is in contrast to previous work which treated PbSe as a stoichiometric compound. The current treatment allows for experimental carrier concentrations to be accurately described within the CALPHAD formalism. In addition to the five-sublattice model, a two-sublattice model is also developed for use in multicomponent databases. Both models show excellent agreement with the experimental data and close agreement with first-principles calculations. These CALPHAD models can be used to determine processing parameters that will result in an optimized carrier concentration and peak zT value.
关键词： CALPHAD,first-principles,DFT,defect chemistry,Thermoelectrics
更新于2025-09-23 15:23:52
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Effect of atom adsorption on the electronic, magnetic, and optical properties of the GeP monolayer: A first-principle study
摘要： First-principles calculations have been carried out to explore the effect of atom surface adsorption on the electronic, magnetic, and optical properties of the germanium phosphide (GeP) monolayer. It is shown that the GeP monolayer exhibits good adsorption capability to all the selected adatoms and can preserve the structural integrity upon the adsorption of most adatoms. The adatoms can bring out diverse electronic properties to the GeP monolayer. The H, Li, Na, K, and Al adatoms donate electrons to the GeP monolayer and result in its metallization. The other adatoms do not change the semiconducting nature of the GeP monolayer and will induce midgap states (Mg, Ca, Si, Ge, Ag, and Au) or reduce the bandgaps (Ni, Pd, and Pt). The B, N, P, As, V, Cr, Mn, Fe, and Co adatoms induce spin magnetic moments into the GeP monolayer. Especially, the spin magnetic moments are mainly located on the adatoms for the GeP decorated with the V, Cr, Mn, Fe, and Co atoms. As a result, the dilute magnetic semiconductor can be obtained. In addition, all the adatoms decrease the work function, except O. Thus, some effects on the optical properties are highly expected. The GeP monolayer exhibits a wide range of light absorption and the Mg, Si, Ge, Cu, Ag, Au, and Pt adatoms can further redshift the absorption edge of the GeP monolayer along the x and y directions. Our calculations provide an effective method to modulate the electronic, magnetic, and optical properties of the GeP monolayer for device applications.
关键词： and optical properties,GeP monolayer,magnetic,First-principles calculations,electronic,atom surface adsorption
更新于2025-09-23 15:23:52
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NO2 and H2 sensing properties for urchin-like hexagonal WO3 based on experimental and first-principle investigations
摘要： An intricate sea-urchin-like hexagonal WO3 nanostructure was synthesized by a facile hydrothermal approach. Sensing properties of the as-fabricated sensor exhibited surpassing response and selectivity for NO2 in comparison of H2 after corroborating the composition, phase-purity and surface morphology using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Formation of the urchin-like structure was ascribed to the capping effects of potassium sulfate that prompts the anisotropic growth of WO3, leading to hierarchical complex with a large surface-volume ratio. In particular, first-principle calculation had provided a new perspective for us to delve into the sensing process of H2 and NO2 from an atomic level. It was found that the sensing properties mainly arose from the tuning of electronic structure and electrons transfer between the adsorbed gas and the sensitized surface along with the charge relocation between them. Finally, a plausible mechanism was proposed as theoretical guidance for achieving high-performance sensors experimentally and supposedly.
关键词： Gas sensing,Surface reaction,First-principles,WO3
更新于2025-09-23 15:23:52
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First-principles study of the electronic structure and optical properties of Eu2+–M (M = Mn2+, Mg2+, Li+) co-doped γ-AlON phosphor
摘要： In our recent work we found γ-AlON:Eu2+ phosphors to hold promise for application in white light-emitting diodes (LEDs). To obtain further insight into Eu2+–M (M = Mn2+, Mg2+, Li+) co-doped γ-AlON, the crystal structure and the electronic and photoluminescence properties of γ-AlON:Eu2+–M (M = Mn2+, Mg2+, Li+) phosphors were studied using first-principle calculations under the framework of density functional theory. Based on the experimental and calculated results, the structure of Eu2+–M (M = Mn2+, Mg2+, Li+) co-doped γ-AlON was established. The calculated results demonstrate that Eu2+ and M (= Mn2+, Mg2+, Li+) can effectively improve the absorption of ultraviolet light by γ-AlON:Eu2+. The absorption coefficient of AlON:Eu2+–Li+ in the ultraviolet blue region of 275–415 nm reached 67,266 cm–1, and the absorption coefficients of AlON:Eu2+–Mn2+ and AlON: Eu2+–Mg2+ at the same doping concentration were 51,219 and 60,575 cm–1, respectively. Our calculations therefore show that the performance of AlON:Eu2+–Li+ is better than AlON:Eu2+–M (M = Mn2+, Mg2+).
关键词： γ-AlON,First principles,Electronic structure,Optical property
更新于2025-09-23 15:23:52
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High-throughput design of functional materials using materials genome approach
摘要： High-throughput computational materials design provides one efficient solution to accelerate the discovery and development of functional materials. Its core concept is to build a large quantum materials repository and to search for target materials with desired properties via appropriate materials descriptors in a high-throughput fashion, which shares the same idea with the materials genome approach. This article reviews recent progress of discovering and developing new functional materials using high-throughput computational materials design approach. Emphasis is placed on the rational design of high-throughput screening procedure and the development of appropriate materials descriptors, concentrating on the electronic and magnetic properties of functional materials for various types of industrial applications in nanoelectronics.
关键词： first-principles,high-throughput,functional materials,materials genome
更新于2025-09-23 15:23:52
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by isovalent doping at the fluorite sublattice
摘要： Bismuth titanate, Bi4Ti3O12 (BiT), is a complex layered ferroelectric material that is composed of three perovskite-like units and one fluorite-like unit stacked alternatively along the transverse direction. The ground-state crystal structure is monoclinic with the spontaneous polarization (～50 μC/cm2) along the plane. BiT typically grows along the c direction in thin-film form, and having the polarization vector aligned with the growth orientation can be beneficial for several potential device applications. It is well known that judicious doping of ferroelectrics is an effective method in adjusting the magnitude and the orientation of the spontaneous polarization. Here, we show using first-principles density-functional theory and a detailed phonon analysis that Bi atoms in the fluorite-like layers have significantly more impact on the magnitude and orientation of the spontaneous polarization vector as compared to the perovskite-like layer. The low-energy hard-phonon modes are characterized by fluorite-like layers experiencing transverse displacements and large changes in Born effective charges on Bi atoms. Thus, the breaking of symmetry caused by doping of Bi sites within the fluorite-like layer leads to the formation of uncancelled permanent dipole moments along the transverse direction. This provides an opportunity for doping the Bi site in the fluorite-like layer. Isovalent dopants P, As, and Sb were studied. P is found to be most effective in the reorientation of the spontaneous polarization. It leads to a threefold enhancement of the out-of-plane component of polarization and to a commensurate rotation of the spontaneous polarization vector by 36.2° towards the transverse direction.
关键词： phonon analysis,doping,ferroelectric,Bi4Ti3O12,first-principles,polarization
更新于2025-09-23 15:23:52