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

TL;DR

This study uses temperature-dependent Raman spectroscopy to investigate phonon anomalies, anharmonic effects, and thermal expansion in few-layer PtS2 and PtSe2, revealing complex vibrational and thermal behaviors relevant for device applications.

Contribution

It provides a detailed analysis of phonon anomalies, interlayer vibrations, and thermal expansion coefficients in PtX2 (X=S, Se), highlighting temperature-dependent vibrational dynamics and anharmonic effects.

Findings

Phonon anomalies observed at specific temperatures indicating vibrational coupling.

Extraction of thermal expansion coefficients for PtS2 and PtSe2.

Identification of interlayer vibrational modes and their temperature dependence.

Abstract

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 thermal and vibrational 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.