Optical Quenching of Photoconductivity in CdS and ZnS Crystals

Abstract

The optical quenching spectrum in CdS and ZnS single crystals has been investigated as a function of temperature, using a high‐resolution monochromator and polarized light. The well‐known spectrum in both materials consists of a narrow band with maximum at about 0.9 eV and a broader band with onset at about 1.1 eV. Poorly resolved fine structure was detected in the 0.9 eV band in CdS between 0.83 and 0.92 eV; no fine structure was detected in the higher‐energy band. No fine structure could be detected in the less accurate measurements on ZnS. No polarization effects of any kind were detected in either material. Studies of the temperature dependence of optical quenching confirm the early indications described by Bube, and indicate anew the intrinsically complex nature of the sensitizing center. The problems related to distinguishing between intrinsic‐defect and copper‐impurity effects are discussed.