Unraveling the phonon scattering mechanism in exfoliated MoSe2 nanosheets using temperature-dependent Raman spectroscopy

The liquid exfoliation method is employed to prepare MoSe2 nanosheets onto silicon (Si) substrates. The vibrational characteristics of MoSe2 nanosheets are elucidated by performing the Raman measurements over the temperature range from 81 to 300 K with a 473 nm laser. The formation of a few monolayer MoSe2 nanosheets is confirmed by XRD, TEM, and XPS before proceeding for temperature-dependent Raman studies. Our experimental investigations demonstrate that the proliferation in temperature brings about a redshift in A(1g) (out-of-plane) and E-2g(1) (in-plane) Raman modes. The obtained values of the first-order temperature coefficients for A(1g) and E-2g(1) modes are - 0.05279 +/- 0.00606 cm(-1) K-1 and - 0.07069 +/- 0.00769 cm(-1) K-1, respectively. We also observed that the Raman shift for both A(1g) and E-2g(1) modes has non-linear temperature dependence. To gain a better perspective regarding the observed nonlinear dependence, a physical model is invoked. Our analytical results indicate that three- and four- phonon anharmonic effects are responsible for the non-linear temperature dependence of Raman modes.