Luminescence of an M center in ZnS?

Abstract

Selected, differently doped and annealed cubic ZnS monocrystals exhibit a structured luminescence in the spectral region between 815 and 1150 nm. At 4 K more than 70 lines with typical linewidths of only 3–5 cm −1 could be resolved. The influence of temperature, of magnetic fields up to B = 10 T, and of irradiation with additional light were studied, and the excitation spectrum was recorded. The experiments indicate for the luminescence center a three-fold excited state and a singlet ground state with a strong phonon coupling, and allow the determination of the position of the involved electronic levels between valence band and conduction band. The results can be explained satisfactorily under the assumption that the center of luminescence consists of two adjacent F + centers, the so-called M center. The present work marks the first time that any such center has been found in a II–VI compound.