Interplay between Anharmonic and Lattice Effects in MoS<sub>2</sub> Nanoflowers: Probing through Temperature-Dependent Raman Spectroscopy
Sonam Rani, Manushree Tanwar, Chanchal Rani, Ravi Bhatia, Rajesh Kumar, I. Sameera
Abstract
Raman spectroscopy has been utilized to understand the structural and vibrational properties of MoS 2 nanoflowers. The temperature-dependent Raman shifts of E 2g 1 and A 1g modes of MoS 2 nanoflowers have been quantified using 633 nm laser excitation in the temperature range 173–498 K. The softening of E 2g 1 and A 1g 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.