Far-infrared study of impurity local modes in Ni-doped PbTe

In this paper, we present far-infrared reflection spectra of Ni doped PbTe single crystal samples. Crystals of PbTe(Ni) were grown by the Bridgman method. These spectra were analyzed using a fitting procedure based on the modified plasmon-phonon interaction model. Together with the strong plasmon-phonon coupling we obtained three local modes of Ni at about 130, 165 and 190 cm−1 which correspond to the impurity atoms in different valence states. The positions of these modes depend on impurity center charge, and their intensities depend on temperature and Ni concentration.