Two-dimensional Sc2O3 monolayer with tunable ultrawide bandgap for solar-blind ultraviolet photodetector

A novel 2D scandia (Sc₂O₃) monolayer was identified using an evolutionary algorithm-based crystal structure prediction method. The Sc₂O₃ monolayer exhibits a $P\bar{3}m1$ symmetry and excellent energetic, thermal, dynamical, and mechanical stability, as well as good mechanical flexibility. The monolayer possesses an ultrawide indirect band gap of 6.246 eV. The monolayer is transparent in the visible light zone, while the large exciton effect leads to significant absorption in the solar-blind and vacuum ultraviolet regions. The band gap of this monolayer can be reduced monotonically by external biaxial tensile strain, resulting in the absorption spectrum covering the entire solar blind spectral region when the load reaches 5.0 %. Additionally, the monolayer has an ultra-high in-plane dielectric constant of approximately 50. The superior stability, flexibility, and strain-tunable electronic and optical properties, as well as the ultra-high dielectric constant, suggest its potential application in a solar-blind photodetector in harsh environments.