Far infrared properties of PbTe doped with cerium

Single crystal samples of lead telluride doped with cerium were made using the Bridgman method. Far infrared reflectivity spectra in the temperature range from 10 to 300K are presented. The experimental data were numerically analyzed using a fitting procedure based on the plasmon-phonon interaction model and optical parameters were determined. Two additional local modes were observed at about 138 and 337 cm(-1). The origin of these local vibrational impurity modes was discussed