A spectroscopical study of stabilization of the sphalerite structure in ZnS:Cu single crystals

Exciton reflection and impurity absorption spectra in ZnS:Cu single crystals at different Cu concentrations have been studied at 77 °K. Free exciton spectra were used to study the transformation of the crystal structure with the Cu content. It has been found that at high Cu concentration a stabilization of the sphalerite structure takes place. At the same concentrations strong additional absorption characteristic of Cu2S crystals can be detected in the visible and near infrared region. The electron microprobe analysis has shown that at high concentrations Cu is distributed in the crystal in the form of strip inclusions. On the basis of the results obtained it is concluded that the stabilization of the sphalerite structure in ZnS:Cu crystals is due to Cu2S crystallization seed centres and not to Cu acceptor centres as it was believed earlier.