Far infrared transmission and structure of Pb---Ge---S semiconducting glasses

Abstract

Lead sulfide has been found to form stable glasses with GeS2 in the presence of GeS. Far-infrared transmission spectra of the glassy compositions x = 0.46, 0.23 and 0.115 in the pseudoternary (PbS)x (GeS2)0.70−x (GeS)0.30 and of the stoichiometric crystalline composition Pb2GeS4 have been observed for the first time. The results indicate a two optical mode behaviour of the compounds. The presence of the heavy lead atom in the Ge---S network seems to appreciably affect the bond bending modes of the GeS4 molecular unit without significantly disturbing its bond stretching vibrations. The presence of S3Ge---GeS3 molecular units in the amorphous compositions and their absence in Pb2GeS4 are indicated.