Experimental verification of the reversibility window concept in binary As-Se glasses subjected to a long-term physical aging

Abstract

Physical aging effects caused by prolonged natural storage $(\ensuremath{\sim}22\text{ }\text{years})$ in binary ${\text{As}}_{x}{\text{Se}}_{100\ensuremath{-}x}$ glasses are probed by temperature-modulated differential scanning calorimetry. It is shown that all aged samples with $x<40$ reveal nonzero out-of-phase component of complex heat flow testifying physical aging effect. The first composition, which can be attributed to a so-called self-organized phase characterized by the absence of natural physical aging effect, is the stoichiometric ${\text{As}}_{2}{\text{Se}}_{3}$ glass; lack of aging within the so-called reversibility window, $28<x<38$, is not found. High-resolution x-ray photoelectron spectroscopy fails to show any evidence of fourfold-coordinated As atoms, which is consistent with the aging ability of glasses with $x<40$.