Phonon anomalies, anharmonicity, and thermal expansion coefficient in few layered PtX2 (X= S, Se): A temperature dependent Raman study

Two-dimensional group-10 noble transition metal dichalcogenides have garnered growing attention due to their rich physical properties and promising applications across nanoelectronics, optoelectronics, and spintronics. Among them, PtX₂ (X = S, Se) exhibits pronounced interlayer coupling driven by hybridization of the out-of-plane Pz orbitals of the chalcogen atoms. In this work, we present a detailed temperature and polarization-resolved Raman spectroscopic study of few-layer PtS₂ and PtSe₂ over the temperature range of ~ 5 to 300 K. Our study encompasses phonon-phonon interactions, symmetry analysis of phonon modes, low-frequency interlayer vibrations, and extraction of thermal expansion coefficients. Notable phonon anomalies in peak position, linewidth, and intensity emerge around ~ 80 K and 150 K for PtS₂, and ~ 70 K and 240 K for PtSe₂, indicating intricate coupling between vibrational and electronic dynamics. These results offer valuable insights for the development of devices based on PtS₂, PtSe₂, and related 2D materials, where interlayer interactions, anharmonic effects, and thermal expansion behaviour play crucial roles.