The TR signal observed in amorphous and crystalline films at 295 K. The insets represent FT spectra obtained from the time-domain data. The frequency of the optical mode is located at 3.70 and 3.62 THz in as-grown (amorphous) and in annealed (crystalline) alloy films, respectively.
(a) The frequency and (b) the revised decay rate of the coherent mode, which is localized in the GeTe layer, in amorphous and crystalline SLs, as a function of the lattice temperatures. In (b) the solid lines are fits to the data with a linear function for the as-grown SL and the anharmonic decay model [Eq. (1) in the original paper] for the annealed SL, giving rise to .