Physica E-low-dimensional Systems & Nanostructures最新文献

Due to semiconductor characteristics and non-volatile ferroelectricity, two-dimensional (2D) In₂Se₃ are considered as potential candidates for next-generation storage and computing devices. Based on first principles calculations, we designed antiferroelectric tunnel junctions (AFTJs) using α-In₂Se₃ as channels. The tunneling barrier height is controlled by the antiferroelectric to ferroelectric (AFE-FE) phase transition of the channel. A maximum current ratio up to 426 is predicted between the AFE and FE phases, enabling the two distinct memory states. By constructing two AFTJs into a calculation unit, the total current can either be fully turned on/off or function as XNOR logic with bias as inputs. Our research provides a new approach to implementing integrated storage and computing devices, making it possible for efficient data-centric applications in the era of big data.

Two-dimensional (2D) multiferroic materials have attracted great interest owing to the integration of ferroelastic and ferromagnetic properties. We identify a novel 2D multiferroic vanadium dioxide (VO₂) monolayer exhibiting a monoclinic phase with a C2/m space group using density functional theory (DFT) calculations. The energetic, dynamic, thermodynamic and mechanical analyses indicate that the monolayer exhibits excellent stability and can be prepared experimentally. The arrangement of the electronic energy bands is analogous to that of a type I heterostructure. The electron doping at a concentration of 0.2 electrons per V atom results in a significant increase in the Curie temperature (T_C) from 11.2 to 184 K estimated by Monte Carlo simulations, and a transition from semiconductor to half-metallicity. In addition, the VO₂ monolayer exhibits 120° ferroelastic switching with a moderate switching energy barrier of 32 meV per atom, subsequently allowing 120° rotation of the easy magnetisation axis. Our work reveals the intrinsic multiferroicity of VO₂, which may provide a guidance on the design of next-generation mechanical/spintronic devices.

Global efforts to combat water pollution, especially from organic dyes like Congo red, emphasize the use of advanced nanomaterials for sewage purification. Metal-Organic Frameworks (MOFs), known for their crystalline structures and versatile properties, have become pivotal in wastewater treatment research. Integrating MWCNTs into MOF derived composite nanostructures is a strategic advancement, boosting the efficiency of photocatalytic systems and addressing environmental concerns. This study details the synthesis of a novel Z-scheme heterojunction nanocomposite (n-ZnO/p-NiO) incorporating multi-walled carbon nanotubes (MWCNTs), achieved via a solvothermal method using metal-organic framework (MOF) as a template. The study uses XRD, FTIR, FESEM, BET, UV, and PL for comprehensive nanocomposite characterization, offering insights into its structural, morphological, and optical properties. The resultant nanocomposite displays high surface area, sturdy pore arrangement, and consistent morphology. MWCNTs influence crystal growth and optical absorption, enhancing surface hydroxyl group concentration and acting as electron acceptors. This results in decreased photo oxidation and improved overall stability under light exposure in the composite. The composite achieves 92 % Congo red degradation in 60 min under UV light, showcasing superior dye adsorption capacity. This underscores its potential as an efficient photocatalyst for environmental remediation and wastewater treatment.

Epitaxial growth of graphene on silicon carbide (SiC) facilitates the direct application of graphene in the semiconductor field. During the graphene preparation process, hydrogen plays a crucial role in determining its morphology. Therefore, studying the influence of hydrogen on the graphene morphology on the SiC surface is of great significance. In this study, we present a direct epitaxial growth of graphene on the SiC(0001) surface under atmospheric pressure. Our focus extends beyond the growth process itself to investigate the important role of hydrogen in shaping the quality and morphology of both the substrate and the graphene. By showing the influence of hydrogen at various stages, our research aims to contribute insights that advance the seamless integration of graphene into the semiconductor field.

By studying the impact of a perpendicular magnetic field $B$ on AB-bilayer graphene (AB-BLG) under dual gating, we yield several key findings for the ballistic transport of gate $U_{\infty }$. Firstly, we discover that the presence of $B$ leads to a decrease in transmission. At a high value of $B$, we notice the occurrence of anti-Klein tunneling over a significant area. Secondly, in contrast to the results reported in the literature, where high peaks were found with an increasing in-plane pseudomagnetic field applied to AB-BLG, we find a decrease in conductivity as $B$ increases. However, it is worth noting that in both cases, the number of oscillations decreases compared to the result in the study where no magnetic field was present $(B=0)$. Thirdly, at the neutrality point, we demonstrate that the conductivity decreases and eventually reaches zero for a high value of $B$, which contrasts with the result that the conductivity remains unchanged regardless of the value taken by the in-plane field. Finally, we consider the diffusive transport with gate $U_{\infty }=0.2{\gamma }_1$ and observe two scenarios. The amplitude of conductivity oscillations increases with $B$ for energy $E$ less than $U_{\infty }$ but decreases in the opposite case $E>U_{\infty }$.

Based on Hubbard model with the Hartree-Fock approximation, we study the properties of quantum discord (QD) between the nearest-neighbor sites A and B in zigzag graphene nanoribbons thermalized with a reservoir at temperature T. Several influences of the site position, on-site Coulomb repulsion U, temperature, and ribbon width on QD are discussed in detail. The results show that QD is robust against thermal fluctuations, and QD for the leg pairs along the zigzag chain near ribbon edges is always larger than that for the rung pairs linking two adjacent zigzag chains. QD for the rung pairs increases and then approaches to saturation as the ribbon width increases, where the velocity of saturation is strongly correlated to U. Moreover, for rung pairs the values of U at the QD peaks perform the scaling behaviors with increasing ribbon width.

The application of black phosphorus in optoelectronic devices is hindered because of its inherent band gap characteristics. In the paper, black phosphorus was prepared by high-energy ball milling, and its related structure and properties were characterized. At the same time, the luminescence mechanism of black phosphorus was explored, and the effect of ultrasonic time on the structure and optical properties of black phosphorus was studied. The luminescence peak of black phosphorus can be modulated to the visible light range after adding polyethylene glycol, and the luminescence of black phosphorus is closely related to the P (020) and P (021). It was found that the luminescence intensity of alcoholized black phosphorus decreases with the increase of ultrasonic time. When the ultrasonic time is 15min, the luminescence intensity of alcoholized black phosphorus decreases greatly, this is because that the content of P (020) in black phosphorus decreases with the increase of ultrasonic time, resulting in the decrease of luminescence intensity.

Using first-principles calculations, we have explored the piezoelectric properties of Janus multilayers and vdW heterostructures based on Janus group-III monochalcogenides. Our calculation results show that all the in-plane and out-of-plane piezoelectricity exists in Janus group-III monochalcogenide multilayers with the atomic radii difference and within intra-layer dipole moments affecting the e₃₃/d₃₃ value. For the vdW heterostructures, the e₃₃ depends on the stacking configuration and increases with the decreasing interlayer distance. Furthermore, the piezoelectric effect properties of the vdW heterostructures are independent of the biaxial strain. Our understanding of how the layer number and vdW integration affect the piezoelectric effect in 2D materials provides theoretical guidance for the experimental application of 2D Janus monolayer and their vdW heterostructures and will also contribute to the development of robust electrical-mechanical-coupled systems with large power densities and energy harvesting capabilities.

The experimentally observed dependencies of the average interwall distances on the number of walls and diameters of multi-walled WS₂ nanotubes were reproduced in molecular mechanics simulations based on a recently developed force field. A common chiral angle was used for all walls inside each nanotube to ensure its one-dimensional periodicity. The data obtained make it possible to determine the nature of changes in the diameters of single-wall components inside the nanotube and variations in the distances between the walls in its inner, middle and outer parts. The stability of multi-walled nanotubes with respect to WS₂ nanolayers and free single-wall components was evaluated.

Finding optimal multi-layer heterostructure configurations that result in desired current–voltage characteristics requires physical control of electron scattering processes. It is shown how a one-dimensional tight-binding Hamiltonian combined with the adjoint method may be employed to explore this non-convex and non-intuitive design space. Such optimal parameter exploration has application to study of vertical electron transport through van der Waals stacked few-layer quantum materials and nano-scale single-crystal semiconductor heterostructures.