Raman spectroscopy study of disorder in cation sublattice of nonstoichiometric and annealed ZnSnN2

This study examines the specific characteristics of Raman scattering observed in ZnSnN2 samples produced via magnetron co-sputtering. The spectra demonstrate a high degree of similarity to the phonon density of states. This phenomenon is caused by the presence of SnZn substitutional defects, which disrupt the ideal crystal structure and generate so-called defect-induced Raman modes across the entire first Brillouin zone. An increase in the elemental content of Sn leads to a decrease in the intensity of the 230 cm⁻1 and 660 cm⁻1 peaks and to their broadening. This suggests an intensification of the disorder within the cation sublattice. Following annealing at 450 °C in a vacuum, an increase in the intensity of the peaks at 450 cm⁻1 and 560 cm⁻1, as well as the Boson peak, was observed. We attribute these changes to the increased formation of Zn–N–Sn bonds within the film structure due to the ordering of the anion (nitrogen) sublattice. However, zinc and tin atoms still occupy random positions in their sublattices, contributing to the overall increase in structural disorder.