THE INFLUENCE OF ANTIMONY IMPURITY ON OPTICAL AND ELECTRICAL-PROPERTIES OF AMORPHOUS SELENIUM

Amorphous Se1-xSbx allor were prepared using a conventional rapid quenching technique. It is found that antimony can only be substituted up to approximately 10 at.% in selen ium to produce Se-Sb glassy alloys. The photoacoustic technique is employed for the first time to determine the optical energy gaps of Se1-xSbx glasses. The optical energy gap of amorphous selenium is found to be 1.99+/-0.02 eV. It reduces drastically on substitution of 2 at.% Sb after which its variation with x is small. The activation energies of Se1-xSbx glasses have been determined from the temperature dependence of their electrical resistivities. The activation energy as a function of x also shows a sudden decrease in the range 0.01 less-than-or-equal-to x less-than-or-equal-to 0.02. Plausible explanations have been suggested based on the Street-Mott model for charged defect states in amorphous chalcogenides.