Core level spectroscopy of Janus zirconium and hafnium dichalcogenide monolayers at the sulfur K and L2,3 edges, including the excitonic effects

Abstract

Focusing on the excitonic effects, the present study deals with the sulfur K and L_2,3 edge spectra of Janus zirconium and hafnium dichalcogenide monolayers and compares with those of the pristine zirconium and hafnium disulfide monolayers and bulks. The changes in the edge spectra are attributed to the changes in the crystal structure, symmetry, and electronic nature of studied dichalcogenides. The phase transition changes the sulfur K and L_2,3 edge X-ray absorption near edge structure (XANES), decreasing the relative spectral intensities and shifting the main peaks to higher energies. Considering the electron-hole coupling reproduces the bound excitonic features and redistributes the oscillator strengths near the edge onsets.