TEMPERATURE-DEPENDENCE OF THE LATTICE-DYNAMICS OF THE LAYERED SEMICONDUCTOR IN2SE3

The temperature dependence of the infrared reflectivity of the layered semiconductor In2Se3 is studied in the range from 10 to 500 cm-1. The behaviour of normal modes is reported from 5 K up to room temperature. Reflectivity spectra are fitted with a four-parameter dispersion model based on the factorized form of the dielectric function. The temperature dependence of the phonon frequencies and damping is reported. An anomaly in the LO frequency which is observed at 160 K, is related with the alpha'-phase transition reported by electron microscopy measurements.