Hexagonal and tetragonal ScX (X = P, As, Sb) nanosheets for optoelectronics and straintronics

The majority of already industrialized and technically feasible materials fall under the category of non-van der Waals (n-vdW) materials. However, the library of two-dimensional (2D) materials typically consists of nanosheets exfoliated from layered bulk (vdW) compounds. In this work, two phases of non-vdW two-dimensional (2D) ScX (X = P, As, Sb) nanosheets, namely hexagonal and tetragonal, have been designed. One potential solution to the severe energy and environmental problems lies in the direct generation of H<inf>2</inf> via photocatalytic water splitting. Herein, using systematic density functional theory (DFT) calculations, we are able to show that the hexagonal nanosheets are strong contenders in this case, as supported by its thermodynamic favourability, suitable exciton binding energy, magnificent optical absorption, water insolubility, high exciton lifetime, and high carrier mobility. Moreover, exciton lifetime ∼100 ns, small exciton radius, and considerable exciton binding energy makes it an embryonic candidate for Bose-Einstein condensation. High sensitivity of the band gap of the tetragonal nanosheets to strain allows bandgap opening under a minor biaxial tensile strain. The tetragonal nanosheets are therefore envisioned to show enormous proficiency in flexible and stretchable nanoelectronics such as strain-based switches, digital data storage devices, movement-controlled sensors, and optoelectronic devices such as 3D printings and displays.