Temperature-dependent Raman spectroscopy studies of 1–5-layer WSe2

In this work, Raman measurements of 1–5-layer WSe2 supported on SiO2/Si in the temperature range of 133 to 533 K are reported. A physical model including both volume effect and temperature effect is used to quantitatively understand the nonlinear temperature dependence of E2g1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rm{E}_{2g}^1$$\end{document} Raman mode. It is found this nonlinear dependence of Raman mode mainly originates from thermal expansion effect and three-phonon scattering. The former effect increases with an increase in number of layers, which is inverse for the latter effect. The temperature-dependent thermal expansion coefficients of 1–5-layer WSe2 are also obtained from Raman spectra. The full width at half maximum (FWHM) of E2g1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rm{E}_{2g}^1$$\end{document} mode is also systematically studied both experimentally and theoretically in the temperature range of 133 to 413 K. It is found that the increase in FWHM of E2g1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\rm{E}_{2g}^1$$\end{document} mode originates from decaying of E2g1 phonon. This work will promote the understanding of anharmonic behaviors of phonons in WSe2 flakes with different thicknesses.