Luminescence and optical spectroscopy of charge transfer processes in solid solutions NiCMg1-CO and NixZn1-xO

In this work photoluminescence spectra for Ni c Mg 1− c O and Ni x Zn 1− x O solid solutions with the rock-salt crystal structure were obtained under synchrotron radiation excitation. Periodical peaks in the photoluminescence excitation spectrum of Ni c Mg 1− c O ( c =0.008) have been discovered for a wide-gap oxide doped with 3d impurities for the first time. They can be considered as LO phonon repetitions of the narrow zero phonon line resulted from the optical transitions into the p–d charge transfer exciton [d 9 h] state. A close coincidence in energy of different peculiarities in the optical absorption and photoluminescence excitation spectra for the Ni c Mg 1− c O and Ni x Zn 1− x O solid solutions is due to the practically equal interatomic distances Ni–O in the investigated materials. The bulk of new experimental results is the trustworthy evidence that only the p–d charge transfer transitions manifest themselves in the spectral region of 3.5–6.5 eV.