Semiconducting two-dimensional group VA-VA haeckelite compounds with superior carrier mobility

Optical excitations of graphene-like materials: group III-nitrides

By using first-principles calculations, we have studied the electronic and optical characteristics of group III-nitrides, such as BN, AlN, GaN, and InN monolayers. The optimized geometry, quasi-particle energy spectra, charge density distributions, band-decomposed charge densities, and Van Hove singularities in density of states are described in the work using physical and chemical pictures and orbital hybridizations found in B-N, Al-N, Ga-N, and In-N chemical bonds. Moreover, the dielectric functions, energy loss functions, absorption coefficients, and reflectance spectra with electron-hole interactions of optical properties are successfully achieved. More importantly, the close relations between electronic and optical properties are successfully demonstrated. The theoretical framework will be useful to research other graphene-like materials.

Semiconductor and topological phases in lateral heterostructures constructed from germanene and AsSb monolayers

Two-dimensional (2D) heterostructures have attracted a lot of attention due to their novel properties induced by the synergistic effects of the constituent building blocks. In this work, new lateral heterostructures (LHSs) formed by stitching germanene and AsSb monolayers are investigated. First-principles calculations assert the semimetal and semiconductor characters of 2D germanene and AsSb, respectively. The non-magnetic nature is preserved by forming LHSs along the armchair direction, where the band gap of the germanene monolayer can be increased to 0.87 eV. Meanwhile, magnetism may emerge in the zigzag-interline LHSs depending on the chemical composition. Such that, total magnetic moments up to 0.49 μ_B can be obtained, being produced mainly at the interfaces. The calculated band structures show either topological gap or gapless protected interface states, with quantum spin-valley Hall effects and Weyl semimetal characters. The results introduce new lateral heterostructures with novel electronic and magnetic properties, which can be controlled by the interline formation.

Haeckelite phosphorus: an emerging 2D allotrope of phosphorus for potential use in LIBs/SIBs

A large surface-to-volume ratio is an essential feature of 2D materials used in many potential electronic applications. This work proposed that the haeckelite-structured phosphorus can be another promising alternative to the known phosphorus allotropes by DFT calculations. This allotrope can be considered a suitable anode material that may provide outstanding performance in LIBs and SIBs. Our simulations confirm that the haeckelite-structured P, composed of alternate square and octagonal rings, is thermally and mechanically stable. The phosphorus haeckelite exhibits a semiconductor with a bandgap of 2 eV and converts to a metallic phase after Li/Na adsorption, which is profoundly the basis for ideal performance of a battery. It provides a high specific capacity and a small OCV with a minimal volume expansion during lithiation/sodiation. The haeckelite-structured P exhibits much higher Li/Na adsorption properties with a small Li/Na migration barrier, which are highly essential in the charge-discharge performance of LIBs/SIBs. Based on the details mentioned above, our study would supply supportive guidelines to advance better opportunities to design and develop flexible Li/Na-ion batteries for future energy conversion and storage applications.