ac conductivity in a-Ge–Se–Bi glasses

In the present paper the effect of Bi impurity (low ∼4 at.% and high ∼10 at.%) on the ac conductivity (σac) of a-Ge20Se80 glassy alloy is studied and the experimentally deduced values are fitted with theoretically deduced values by using correlated barrier hopping model (CBH). Frequency dependent ac conductance of the samples over a frequency range of 100–50 kHz has been taken in the temperature range (268–360 K). At frequency 2 kHz and temperature 298 K, the value of ac conductivity (σac) decreases at low concentration of Bi (4 at.%). However, the value of σac increases at higher concentration of Bi (10 at.%). The ac conductivity is proportional to ωs for undoped and doped samples. The value of frequency exponent (s) decreases as the temperature increases. These results have been explained on the basis of some structural changes at low and high concentration of Bi impurity.