Tuning of the electronic and photocatalytic properties of Janus WSiGeZ4 (Z = N, P, and As) monolayers via strain engineering

Abstract

Recently, MA₂Z₄ materials have received tremendous attention due to their amazing electronic, spintronic, and optoelectronic properties. In this work, we propose a class of 2D Janus materials WSiGeZ₄ (Z = N, P, and As). It was found that their electronic and photocatalytic properties are sensitive to the change of the Z element. Biaxial strain results in an indirect–direct band gap transition in WSiGeN₄ and a semiconductor–metal transition in WSiGeP₄ and WSiGeAs₄. Comprehensive studies demonstrate that these transitions as well as valley-contrasting physics are closely related to the crystal field induced orbital distribution. By taking into account several features of the excellent photocatalysts reported for water splitting, we predict three promising photocatalytic materials WSi₂N₄, WGe₂N₄, and WSiGeN₄. Their optical and photocatalytic properties can be well modulated by applying biaxial strain. Our work not only provides a class of potential electronic and optoelectronic materials but also enriches the study of Janus MA₂Z₄ materials.