Experimental observation of highly anisotropic elastic properties of two-dimensional black arsenic

TL;DR

This study experimentally demonstrates the highly anisotropic elastic properties of two-dimensional black arsenic, revealing significant differences in Young's modulus and ultimate strain along different crystallographic directions, which were previously only theoretically predicted.

Contribution

The paper provides the first experimental validation of black arsenic's anisotropic elastic properties using a novel in situ tensile setup, confirming theoretical predictions.

Findings

Young's modulus along zigzag is ~1.6 times greater than along armchair

Ultimate strain anisotropy ratio reaches ~2.5

Experimental method enables detailed mechanical characterization of 2D anisotropic materials

Abstract

Anisotropic two-dimensional layered materials with low-symmetric 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 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 zigzag direction was ~1.6 times greater than that along armchair direction, while the anisotropic ratio of ultimate strain reached ~2.5, attributed to hinge structure in armchair direction. This study could provide significant insights to design novel anisotropic materials and explore their potential applications in nanomechanics and nanodevices.