Electron-Spin-Resonance Studies in ZnS:Ge and ZnS:Si

Photosensitive electron-spin-resonance signals due to Ge³⁺ and Si³⁺ in ZnS are observed. These signals are much enhanced under uv excitation and quickly decreased by irradiation of light of longer wavelengths. It is found that for Ge³⁺ in cubic ZnS, g=2.0086±0.0003 and A=305×10^-4 cm^-1; for Si³⁺ in cubic ZnS, g=2.0047±0.0003 and A=654×10^-4 cm^-1. A molecular-orbital treatment of the unpaired-electron wave functions satisfactorily accounts for the sign and the order of magnitude of the observed g values. The correlation of the photosensitivity of resonance signals with the luminescence observed in these samples is discussed.