First-principles study of the structure, electronic and optical properties of monolayer ZrX₃ (X = S, Se, Te)

The structure, electronic and optical properties of single-layer transition metallic chalcogenides ZrX₃ (X = S, Se, Te) have been studied by density functional theory. The electron energy dispersion curve shows that ZrX₃ has semiconductor properties, in which the conduction band is mainly contributed by the correlated states of the Zr-d orbital, and the valence band is mainly contributed by the correlated states of the X-p orbital. It is found that b-axis and biaxial strain have great influence on the bandgap and the shift of density of states is also large. At the same time, the peak value of density of states increases greatly when biaxial strain is applied. It is of guiding significance for selecting suitable substrates to prepare two-dimensional ZrX₃ materials to study their electronic properties. The calculation of optical constants confirms that ZrX₃ has strong optical anisotropy. In the visible range, the light absorption efficiency of ZrX₃ in the direction of electric field polarization [100] is higher than that in the direction of [010]. The reflectance spectral results show that ZrS₃ and ZrSe₃ in the [100] directions have the highest reflectance, and ZrTe₃ in the [010] direction has the highest reflectance, even in the long electromagnetic radiation range (up to 10 eV), which is of great significance for the construction of visible optical devices.

All computations have been carried out based on density functional theory (DFT) as implemented in the CASTEP code. The pseudo-potential is adopted by the norm conserving, and the exchange correlation functional is adopted by the Perdew-Burke-Ernzerhof in local generalized gradient approximation (GGA).