Density Functional Theory Study of Layer-Controlled Band Gap and Strong Anisotropic Properties in ScSI Nanosheet: Implications for Photoelectric Sensor

Moderate band gap and high stabilities are key properties in (opto)electronic devices application. Based on first-principles calculations, we predicted an ultrathin two-dimensional (2D) semiconductor, namely, a ScSI nanosheet, with tunable electronic properties and high stabilities. The ScSI monolayer is an indirect semiconductor with a band gap of 2.59 eV, and significantly, this monolayer can shift from an indirect to direct band gap under small strains. Moreover, the cleavage energy of the ScSI monolayer is lower than that of graphene, and this monolayer possesses high dynamical, thermal, and mechanical stabilities, suggesting the possibility of mechanical exfoliation experimentally. Interestingly, due to the quantum confinement effect, the band gaps of the ScSI nanosheets exhibit a layer-dependent exponential decay relationship with an increasing number of layers. The exceptional properties render ScSI nanosheets a promising candidate for flexible applications in optoelectronic devices especially in photoelectric sensors.