Band gap modulation of a new Janus–non-Janus hybrid MoSSe monolayer: a DFT study

Abstract The family of two-dimensional molybdenum-based transition-metal dichalcogenides has recently grown to include Janus and non-Janus structures, which offer unique properties for nanoelectronic and optoelectronic applications. This study took this a step further by introducing the new Hybrid-I MoSSe, which is a combination of Janus and non-Janus MoSSe monolayers. Based on density functional theory calculations, the Hybrid-I MoSSe monolayer exhibited higher stability than the conventional Janus MoSSe and Hybrid-II MoSSe, as indicated by cohesive energy and phonon dispersion analyses. It exhibited a direct band gap of 1.54 eV, which reduced to 1.44 eV with spin-orbit coupling . Calculation of the optical properties indicated that the Hybrid-I MoSSe monolayer had high absorption and low reflectivity in the visible spectrum, enhancing its potential for solar cell and photodetector applications. Various methods for band gap modulation, including biaxial strain, external electric fields, layer thickness variation, and heterostructure formation, demonstrated effective control over electronic properties. For example, a shift from direct to indirect band gaps occurred at a tensile stress of 4% and compressive stress of -8%. This transition also occurred in Hybrid-I-non-Janus MoSSe and both Hybrid-I-Janus MoSSe heterostructures. Our results demonstrate that the Hybrid-I MoSSe monolayer combines stability with tunable electronic properties, making it a promising candidate material for the next generation of nanoelectronics and optoelectronics applications.