- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
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
-
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
-
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
-
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
-
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
-
Semimetallicity and Negative Differential Resistance from Hybrid Halide Perovskite Nanowires
摘要： In the rapidly progressing field of organometal halide perovskites, the dimensional reduction can open up new opportunities for device applications. Herein, taking the recently synthesized trimethylsulfonium lead triiodide (CH3)3SPbI3 perovskite as a representative example, first-principles calculations are carried out and the nanostructuring and device application of halide perovskite nanowires are studied. It is found that the 1D (CH3)3SPbI3 structure is structurally stable, and the electronic structures of higher-dimensional forms are robustly determined at the 1D level. Remarkably, due to the face-sharing [PbI6] octahedral atomic structure, the organic ligand-removed 1D PbI3 frameworks are also found to be stable. Moreover, the PbI3 columns avoid the Peierls distortion and assume a semimetallic character, contradicting the conventional assumption of semiconducting metal-halogen inorganic frameworks. Adopting the bundled nanowire junctions consisting of (CH3)3SPbI3 channels with sub-5 nm dimensions sandwiched between PbI3 electrodes, high current densities and large room-temperature negative differential resistance (NDR) are finally obtained. It will be emphasized that the NDR originates from the combination of the near-Ohmic character of PbI3-(CH3)3SPbI3 contacts and a novel NDR mechanism that involves the quantum-mechanical hybridization between channel and electrode states. This work demonstrates the great potential of low-dimensional hybrid perovskites toward advanced electronic devices beyond actively pursued photonic applications.
关键词： semimetals,halide perovskite nanowires,first-principles calculations,negative differential resistance
更新于2025-09-23 15:22:29
-
AIP Conference Proceedings [Author(s) DAE SOLID STATE PHYSICS SYMPOSIUM 2017 - Mumbai, India (26–30 December 2017)] - First principles calculations for interaction of tyrosine with (ZnO)3 cluster
摘要： First Principles Calculations have been performed to study interactions of Phenol ring of Tyrosine (C6H5OH) with (ZnO)3 atomic cluster. All the calculations have been performed under the Density Functional Theory (DFT) framework. Structural and electronic properties of (ZnO)3/C6H5OH have been studied. Gaussian basis set approach has been adopted for the calculations. A ring type most stable (ZnO)3 atomic cluster has been modeled, analyzed and used for the calculations. The compatibility of the results with previous studies has been presented here.
关键词： (ZnO)3 cluster,Tyrosine,First Principles Calculations,Density Functional Theory,Gaussian basis set
更新于2025-09-23 15:21:21
-
Theory-Driven Heterojunction Photocatalyst Design with Continuously Adjustable Band Gap Materials
摘要： The utilization efficiency of hot carriers in photocatalyst is limited at present by their fast recombination. Heterojunction interface would reduce the recombination rate by effectively facilitating spatial separation of the hot electron and hole. Here, we establish a heterojunction photocatalyst design principle by using continuously adjustable band gap materials. This is demonstrated using first-principles calculations, and is subsequently validated by direct measurements of photocatalytic activity of ZnxCd1-xS-reduced graphene oxide (RGO) heterojunction as a proof-of-concept photocatalyst. Tuning the Zn/Cd ratio and/or the reduction degree of RGO can result into three types of heterojunction, and different conduction and valence band offsets by varying their band gap and positions of band edges. The modulation of efficient electron-hole separation at the interface is manifested by the consistency of calculated and experimental optical absorbance, and enhanced photocatalytical activity of ZnxCd1-xS-RGO heterojunction. This results can also rationalize the available experimental results of RGO-based composites. This design principle is broadly applicable to the development of other heterojunction materials ranging from photocatalysts and solar cells to functional electronic devices through interfacial band alignment engineering.
关键词： band gap,photocatalytic activity,RGO,heterojunction,ZnxCd1-xS,photocatalyst,first-principles calculations
更新于2025-09-23 15:21:21
-
Recipe for Dirac Phonon States with a Quantized Valley Berry Phase in Two-Dimensional Hexagonal Lattices
摘要： The topological quantum states in two-dimensional (2D) materials are fascinating subjects of research, which usually highlight electron-related systems. In this work, we present a recipe that leads to Dirac phonon states with quantized valley Berry phase in 2D hexagonal lattices by first-principles calculations. We show that candidates possessing the three-fold rotational symmetry at the corners of the hexagonal Brillouin zone host valley Dirac phonons, which are guaranteed to remain intact with respect to perturbations. We identify that such special topological features populated by Dirac phonons can be realized in various 2D materials. In particular, the monolayer CrI3, an attractive 2D magnetic semiconductor with exotic applications in spintronics, is an ideal platform to investigate nontrivial phonons in experiments. We further confirm that the phonon Berry phase is quantized to ±π at two inequivalent valleys. The phonon edge states terminated at the projection of phonon Dirac cones are clearly visible. This work demonstrates that 2D hexagonal lattices with attractive valley Dirac phonons will extend the knowledge of valley physics, providing wide applications of topological phonons.
关键词： Dirac phonons,first-principles calculations,valley Berry phase,phonon edge states,2D hexagonal lattices
更新于2025-09-23 15:21:21
-
Effective Hamiltonian of Topological Nodal Line Semimetal in Single-Component Molecular Conductor [Pd(dddt) <sub/>2</sub> ] from First-Principles
摘要： Using ?rst-principles density-functional theory calculations, we obtain the non-coplanar nodal loop for a single-component molecular conductor [Pd(dddt)2] consisting of HOMO and LUMO with di?erent parity. Focusing on two typical Dirac points, we present a model of an e?ective 2 × 2 matrix Hamiltonian in terms of two kinds of velocities associated with the nodal line. The base of the model is taken as HOMO and LUMO on each Dirac point, where two band energies degenerate and the o? diagonal matrix element vanishes. The present model, which reasonably describes the Dirac cone in accordance with the ?rst-principles calculation, provides a new method of analyzing electronic states of a topological nodal line semimetal.
关键词： topological nodal line semimetal,effective Hamiltonian,Dirac cone,single-component molecular conductor,first-principles calculations
更新于2025-09-23 15:21:21