Quantitative analysis of temperature-dependent vibrational properties of Cobalt incorporated WSe2 ternary alloy

The present work highlights the growth and a detailed analysis of temperature and laser power-dependent Raman spectra of Co incorporated WSe2 crystals. Morphological confirmations of the DVT-grown crystals were obtained from SEM and HRTEM, while their elemental confirmation was obtained from XPS. XRD enabled in identifying their hexagonal crystal structure. Raman spectra analysis of the samples was carried out over a temperature range of 298–93 ​K. A model including contributions from the pure volume and temperature effects has been followed to quantitatively analyze the non-linearity in the temperature dependence of the prominent A1g and E2g Raman modes. Based on this the thermal expansion coefficients of these multilayer crystals have been deduced for the first time. The three-phonon process was confirmed to contribute predominantly to the non-linearity, with comparatively weak contributions from the four-phonon process and thermal expansion effect. The thermal conductivity of the samples is deduced from the laser power-dependent Raman spectra. The work is expected to promote the understanding of the anharmonic behaviour of phonons in the crystals of WSe2 and Co0.5W0.5Se2.