Factors affecting the negative Poisson's ratio of black phosphorus and black arsenic: electronic effects

Experimental Observation of Highly Anisotropic Elastic Properties of Two-Dimensional Black Arsenic

Anisotropic two-dimensional layered materials with low-symmetry lattices have attracted increasing attention due to their unique orientation-dependent mechanical properties. Black arsenic (b-As), with the puckered structure, exhibits extreme in-plane anisotropy in optical, electrical, and thermal properties. However, experimental research on mechanical properties of b-As is very rare, although theoretical calculations predicted the exotic elastic properties of b-As, such as the anisotropic Young's modulus and negative Poisson's ratio. Herein, experimental observations on highly anisotropic elastic properties of b-As were demonstrated using our developed in situ tensile straining setup based on the effective microelectromechanical system. The cyclic and repeatable load-displacement curves proved that Young's modulus along the zigzag direction was ∼1.6 times greater than that along the armchair direction, while the anisotropic ratio of ultimate strain reached ∼2.5, attributed to the hinge structure in the armchair direction. This study could provide significant insights into the design of novel anisotropic materials and explore their potential applications in nanomechanics and nanodevices.

New two-dimensional arsenene polymorph predicted by first-principles calculation: robust direct bandgap and enhanced optical adsorption

In this work, we predict a new polymorph of 2D monolayer arsenic. This structure, namedδ-As, consists of a centrosymmetric monolayer, which is thermodynamically and kinetically stable. Distinctly different from the previously predicted monolayer arsenic with an indirect bandgap, the new allotrope exhibits a direct bandgap characteristic. Moreover, while keeping the direct bandgap unchanged, the bandgap of monolayerδ-As can be adjusted from 1.83 eV to 0 eV by applying zigzag-direction tensile strain, which is pronounced an advantage for solar cell and photodetector applications.