Spectroscopic valuation of phonon lifetime and surface characteristics of Zn_0.96Mg_0.04S thin film

The anharmonic properties of the longitudinal optical (LO) phonon mode of Mg-doped ZnS (Zn0.96 Mg0.04S) are investigated using the Balkanski and Klemens models on the temperature-dependent Raman spectra. The variation in the position of the Raman line, peak width, and phonon lifetime with temperature was fitted using three and four phonon decay mechanisms. The values of the anharmonic fitting parameters indicated low anharmonicity. A lifetime of ∼0.17 ps at 90 K indicated a fast phonon decay. In addition, the thin film is analyzed to evaluate its surface characteristics using Raman mapping that showed chemical homogeneity over a large area of the film. Furthermore, we analyzed spatial variations of Raman line intensity, peak area, linewidth, and line position of the LO phonon mode. Raman analysis helped in understanding the phonon-phonon interaction mechanism in Zn0.96 Mg0.04S thin films.