Interplay between Anharmonic and Lattice Effects in MoS2 Nanoflowers: Probing through Temperature-Dependent Raman Spectroscopy

Abstract

Raman spectroscopy has been utilized to understand the structural and vibrational properties of MoS2 nanoflowers. The temperature-dependent Raman shifts of E2g1 and A1g modes of MoS2 nanoflowers have been quantified using 633 nm laser excitation in the temperature range 173-498 K. The softening of E2g1 and A1g modes with the increase in temperature has been observed. The experimental results indicate that both modes vary linearly with temperature. Further, by using a semiquantitative model, individual contributions of true anharmonic and quasi-harmonic parts to the temperature-dependent Raman shifts of both modes have been quantified. The true anharmonicity was found to be more dominating than quasi-harmonicity. The three- and four-phonon processes determined the true anharmonicity, while the thermal expansion coefficient plays a major role in quantifying the quasi-harmonic contribution. In this work, we have shown the variation in the behavior of quasi-harmonicity by considering the thermal expansion as a function of temperature and its correlation in quantifying the three- and four-phonon parts. © 2023 American Chemical Society.