On the compositional trend of photodarkening GexSe1-x

Abstract

Glassy GexSe1-x samples were prepared from 5N purity elements. The expansion coefficient (αp) and optical transmission of virgin and illuminated samples (halogen lamp at room temperature) have been studied. The extreme values of photodarkening are shifted into Se-rich region, somewhere close to x = 0.2. All the dependences (relative changes of Urbach edge slope, atomic volume (Vm) and expansion coefficient (αp) in the temperature range from 40 to 80 °C versus atomic fraction of Ge) indicate an extreme around x ≈ 0.2 in the region of the Philips threshold, where the mean coordination number of pseudoatom is: 〈CN〉 = 2.4.