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- 实验方案
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Two-Dimensional Electronics and Optoelectronics: Present and Future
摘要： Since the successful isolation of graphene a little over a decade ago, a wide variety of two-dimensional (2D) layered materials have been studied. They cover a broad spectrum of electronic properties, including metals, semimetals, semiconductors, and insulators. Many of these 2D materials have demonstrated promising potential for electronic and optoelectronic applications.
关键词： transition metal dichalcogenides,black phosphorus,optoelectronics,electronics,two-dimensional materials,graphene
更新于2025-09-09 09:28:46
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Band structure and giant Stark effect in two-dimensional transition-metal dichalcogenides
摘要： We present a comprehensive study of the electronic structures of 192 configurations of 39 stable, layered, transition-metal dichalcogenides using density-functional theory. We show detailed investigations of their monolayer, bilayer, and trilayer structures’ valence-band maxima, conduction-band minima, and band gap responses to transverse electric fields. We also report the critical fields where semiconductor-to-metal phase transitions occur. Our results show that band gap engineering by applying electric fields can be an effective strategy to modulate the electronic properties of transition-metal dichalcogenides for next-generation device applications.
关键词： two-dimensional materials,band structure,giant-Stark effect,density functional theory,electric field,transition metal dichalcogenides
更新于2025-09-09 09:28:46
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Numerical Modeling of the Static Electric Field Effect on the Director of the Nematic Liquid Crystal Director
摘要： A two-dimensional model of the Frederiks effect is used to investigate the static electric field effect on the orientation of the nematic liquid crystal (LC) director in a side-electrode cell. The solutions are obtained by the standard finite-difference methods. The programs for the numerical solution of a two-dimensional parabolic partial differential equation are developed both in FORTRAN and C/C++. The Frederiks transition threshold for the central part of the cell and the dependences of the director’s orientation distribution on a high electric field are obtained. The results of the calculation are compared with the experimental data.
关键词： nematic liquid crystal,two-dimensional model of the Fredericks effect,finite-difference methods,electric field,director,numerical solution
更新于2025-09-09 09:28:46
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Excitonic effects on layer- and strain-dependent optoelectronic properties of PbI2
摘要： Exciton states have obvious effects on optical properties of two-dimensional (2D) materials. Here, we investigate excitonic effects on electronic and optical properties of PbI2 by using GW + Bethe-Salpeter equation method, considering the layer number and strain effect. These studies show that exciton states obviously modify and dominate the optical absorption of 2D PbI2 nanosheets. Also, with the increasing number of layers, the intensity of main absorption peak increases and the exciton binding energy decreases. Meanwhile, the tensile strain can induce the threshold energy of optical spectra shift down the low energy, and exciton binding energy has a maximum at the strain of 3%. Therefore, our results indicate that the 2D PbI2 nanomaterials have excellent ultraviolet absorption and corresponding potential for the application of optoelectronic devices.
关键词： Optical property,Electronic structure,Lead iodide,Excitonic effects,Two-dimensional semiconductor
更新于2025-09-09 09:28:46
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Revealing the Spectrum of Unknown Layered Materials with Super-Human Predictive Abilities
摘要： We discover the chemical composition of over 1000 materials that are likely to exhibit layered and two-dimensional phases but have yet to be synthesized. This includes two materials our calculations indicate can exist in distinct structures with different band gaps, expanding the short list of two-dimensional phase change materials. While databases of over 1000 layered materials have been reported, we provide the first full database of materials that are likely layered but yet to be synthesized, providing a roadmap for the synthesis community. We accomplish this by combining physics with machine learning on experimentally obtained data and verify a subset of candidates using density functional theory. We find our model performs five times better than practitioners in the field at identifying layered materials and is comparable or better than professional solid-state chemists. Finally, we find that semi-supervised learning can offer benefits for materials design where labels for some of the materials are unknown.
关键词： two-dimensional materials,machine learning,materials discovery,density functional theory,layered materials
更新于2025-09-09 09:28:46
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Thermopower of a Two-Dimensional Semimetal in a HgTe Quantum Well
摘要： The thermopower in a two-dimensional semimetal existing in HgTe quantum wells 18–21 nm thick has been studied experimentally and theoretically for the first time. It has been found theoretically and experimentally that the thermopower has two components—diffusion and phonon-drag—and that the second component is several times larger than the first. It has been concluded that the electron–hole scattering plays an important role in both mechanisms of the thermopower.
关键词： diffusion,thermopower,HgTe quantum wells,two-dimensional semimetal,phonon-drag,electron–hole scattering
更新于2025-09-09 09:28:46
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with pentagonal structure
摘要： Structure-property relationships have always been guiding principles for materials discovery. Here we explore the relationships to discover two-dimensional (2D) materials with the goal of identifying 2D magnetic semiconductors for spintronics applications. In particular, we report a density functional theory + U study of single-layer antiferromagnetic (AFM) semiconductor CoS2 with the pentagonal structure forming the so-called Cairo tessellation. We ?nd that this single-layer magnet exhibits an indirect band gap of 1.06 eV with electron and hole effective masses of 0.52 and 1.93 m0, respectively, which may lead to relatively high electron mobility. The hybrid density functional theory calculations correct the band gap to 2.24 eV. We also compute the magnetocrystalline anisotropy energy (MAE), showing that the easy axis of the AFM ordering is along the b axis with a sizable MAE of 153 μeV per Co ion. We further calculate the magnon frequencies at different spin-spiral vectors, based on which we estimate the N′eel temperatures to be 20.4 and 13.3 K using the mean ?eld and random phase approximations, respectively. We then apply biaxial strains to tune the band gap of single-layer pentagonal CoS2. We ?nd that the energy difference between the ferromagnetic and AFM structures strongly depends on the biaxial strain, but the ground state remains the AFM ordering. Although the low critical temperature prohibits the magnetic applications of single-layer pentagonal CoS2 at room temperature, the excellent electrical properties may ?nd single-layer semiconductor applications in optoelectronic nanodevices.
关键词： two-dimensional materials,magnon frequencies,N′eel temperature,biaxial strain,Cairo tessellation,antiferromagnetic semiconductor,density functional theory,band gap,magnetocrystalline anisotropy energy,pentagonal structure,spintronics
更新于2025-09-09 09:28:46
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Oxygen Vacancy-Rich Ultrathin Sulfur-Doped Bismuth Oxybromide Nanosheet as a Highly Efficient Visible-Light Responsive Photocatalyst for Environmental Remediation
摘要： Designing ultrathin two-dimensional (2D) defective materials and metal-free doped materials as photocatalysts both have received enormous attentions in the field of environmental remediation due to their great potential for removing colorless contaminants. However, whether the synergism of defects and metal-free doping exists and the corresponding oxidative mechanism is unclear, which retard further developments of high performance catalysts. Here, a novel oxygen vacancy (OV)-rich ultrathin sulfur-doped BiOBr nanosheet (BB-xS) was synthesized through a facile one-step solvothermal method. Under visible light irradiation, the optimal BB-5S sample exhibited 98% degradation efficiency of 4-chlorophenol (4-CP) within 120min, which was 4.9 and 18.0 times greater than that of pristine ultrathin BiOBr and oxygen vacancy-poor sulfur-doped BiOBr, respectively. Also, this excellent photoactivity could extend to other colorless organic contaminants, such as bisphenol analogues and sulfonamides, verifying the universal applicability of BB-xS. Based on experimental results and density functional theory (DFT) calculations, it was manifested that a sub-band was generated via the synergistic effect of oxygen vacancies and sulfur doping, and it greatly enhanced the visible-light absorption capability and suppressed the photoinduced charge recombination, which would be beneficial to improve the photocatalytic activity. Additionally, the corresponding photocatalytic degradation pathway of 4-CP was also proposed. This work can provide a new protocol for the design and construction of highly active photocatalysts toward environmental remediation.
关键词： photocatalytic degradation,Ultrathin two-dimensional nanosheets,sulfur-doped,oxygen vacancy,colorless organic contaminants
更新于2025-09-09 09:28:46
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Prediction of two-dimensional organic topological insulator in metal-DCB lattices
摘要： Based on first-principles calculations, we systematically investigated a two-dimensional (2D) organometallic framework consisting of metal atoms (elements from groups IIIA, IVA, VA, VIA, IB, and Pt) and dicyanobenzenes (DCBs). Our stability analysis showed that the system prefers the buckled structure in metals with p-orbital valence electrons, whereas in metals with d-orbitals, the planar phase is preferable. Topological invariants (Z2) of these systems were calculated, and they are identified as 2D intrinsic organic topological insulators. Au- and Bi-DCB are exemplar materials with the largest bandgaps within IB and VA groups. Moreover, Au-DCB exhibits robustness of its topological phase against strain. Furthermore, the topologically protected edge states in Au-DCB are identified to further verify the Z2 invariant. Interestingly, utilizing hole doping in Bi-DCB leads to a nearly flat Chern band and results in the quantum anomalous Hall phase. Our results suggest that these organometallic frameworks are promising for potential applications in quantum spintronics with the merits of low cost and ease of synthesis.
关键词： first-principles calculations,organic topological insulator,quantum spintronics,metal-DCB lattices,two-dimensional
更新于2025-09-09 09:28:46
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Initial Design of Phase-Frequency Scanned Array Using CRLH Leaky-Wave Antennas
摘要： Initial design of phase-frequency scanned array using composite right/left-handed (CRLH) waveguide leaky-wave antennas (LWAs) is studied in this paper. The array consists of 32 frequency scanning CRLH LWAs that are fed by a phased feed system. Two-dimensional (2D) beam steering capability is achieved in the plane normal to the array aperture and verified by the full-wave simulations. This array is capable of scanning to 61° from backward to forward directions in the frequency-scan plane and 17° in the phase-scan plane. The beamwidth is approximately 2° with ?20 dB sidelobe level (SLL) in the frequency-scan plane and 2.5° with maximum ?10 dB SLL in the phase-scan plane. Compared with traditional 2D scanning array, the feed system of this phase-frequency scanned array can be simplified significantly.
关键词： phase-frequency scanned array,leaky-wave antenna (LWA),two-dimensional (2D) beam steering,composite right/left-handed (CRLH),phased array
更新于2025-09-09 09:28:46