Quantitative Evaluation of Nonlinear Temperature Dependence of Raman Shift in Exfoliated WSe2 Nanosheets

Raman measurements in the temperature range from 81 K to 433 K have been carried out on exfoliated WSe2 nanosheets fabricated by the liquid exfoliation technique and supported on silicon (Si) substrate. An analytical model incorporating the volume and temperature effects is invoked quantitatively to provide insight into the nonlinear temperature dependence of the A1g Raman mode. The results indicate that the first-order temperature coefficient of the A1g mode of WSe2 nanosheets is −0.00695 ± 5.719 × 10−4 cm−1 K−1. Our results show that the vibrational characteristics of transition-metal dichalcogenides (TMDs) are governed by anharmonic effects such as thermal expansion and three-phonon scattering. We believe that these findings will advance comprehension of the anharmonic behavior of phonons in WSe2 nanosheets for use in various optoelectronic applications.