Temperature induced phonon behaviour in germanium selenide thin films probed by Raman spectroscopy

Here we report a detailed study of temperature-dependent phonon properties of exfoliated germanium selenide thin films (several tens of nanometers thick) probed by Raman spectroscopy in the 70–350 K temperature range. The temperature-dependent behavior of the positions and widths of the Raman modes was nonlinear. We concluded that the observed effects arise from anharmonic phonon–phonon interactions and are explained by the phenomenon of optical phonon decay into acoustic phonons. At temperatures above 200 K, the position of the Raman modes tended to be linearly dependent, and the first order temperature coefficients χ were −0.0277, −0.0197 and −0.031 cm−1 K−1 for B3g, Ag(1) and Ag(2) modes, respectively.