Low-Temperature ac Conductivity of Chalcogenide Glasses

Abstract

The conductivity of amorphous ${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$ and ${\mathrm{As}}_{2}$${\mathrm{Te}}_{3}$Ge was measured down to 4.2 K at frequencies ranging between 0.1 and 100 kHz. The ac conductivity below 100 K, which is totally unaffected by the dc conductivity, is proportional to ${\ensuremath{\omega}}^{s}{T}^{n}$ with $s=1$ and $n\ensuremath{\simeq}0.5$ for as-deposited films and $n\ensuremath{\simeq}0.1$ for annealed films. These experiments are interpreted in terms of Elliott's theory based on electron pairs hopping over a barrier between both paired and random defects.