Absorption edge in silica glass

Abstract

Vacuum ultraviolet absorption measurement was carried out in silica glass over a wide temperature range from 4 to 1900 K, and structure of the absorption edge and its origin have been elucidated. The main factor that determines the Urbach tail of silica glass is the thermal vibration rather than the structural disorder frozen-in at the glass transition temperature, resulting in a strong temperature dependence of the absorption edge far below the glass transition temperature. Furthermore, freezing process of the disorder from the viewpoint of electronic structure was observed.