Novel two-dimensional HfSi₂N₄ monolayer with excellent bandgap modulation and electronic properties modulation

The bandgap modulation and electronic properties modulation of two-dimensional HfSi₂N₄ monolayer induced by strain, electric field and atomic adsorption are studied by first principles. The HfSi₂N₄ monolayer was found to be dynamically, thermally, and mechanically stable at equilibrium, and it is a direct semiconductor with a bandgap of 1.87 eV. The bandgap of the HfSi₂N₄ monolayer can be precisely modulated by strain. Under the action of strain, HfSi₂N₄ monolayer not only transforms from direct semiconductor to indirect semiconductor, but also improves the absorption of visible light. An external electric field in the 0-0.5 eV/Å range can also modulate the bandgap of HfSi₂N₄ monolayer from 1.87 eV to 0 eV, and most importantly, at an external electric field of 0.5 eV/Å, HfSi₂N₄ monolayer shows the characteristics of spin gapless semiconductor. The calculated adsorption energy shows that the structures of H, O and F atoms adsorbed by HfSi₂N₄ monolayer can all exist stably. The bandgap of the configuration after adsorption of O and F atoms is significantly reduced compared with that of HfSi₂N₄ monolayer. Furthermore, the HfSi₂N₄ monolayer after adsorption of H and F atoms is transformed into a magnetic semiconductor. METHOD: All calculations were performed using Vienna ab initial simulation package, The electronic structure, mechanical properties, electronic properties and other properties were carried out using generalized gradient approximation (GGA-PBE), supplemented by HSE06 and GGA + U. The total-energy and force convergence are less than 10^-6 eV and 0.001 eV/Å, respectively. The vacuum on the z-axis is selected 20 Å. The vdW interactions were corrected using the Grimme scheme (DFT-D3).