Relaxation Dynamics in Chalcogenide Glasses

Across the glass-transition temperature, Tg, glass formers are characterized by two main relaxation processes, the α and the β-relaxation. The former is related to cooperative structural rearrangements and is substantially frozen below Tg; the latter process is a quasi-localized, thermally-activated process which remains active also below Tg, in the glass state. This thesis work aims to employ a Photon-Correlation Imaging (PCI) setup to study the relaxation dynamics in different types of glasses at temperatures across Tg. In particular, it is based on a 1064nm laser, which opens the possibility to study amorphous semiconductors, since they are typically opaque in the visible range. The main advantage of this configuration resides in the possibility to probe the relaxation processes in different parts of the sample, allowing to extract direct information on the characteristic timescale of the process. The temporal range that can be probed with this technique - from milliseconds to hours - is notoriously difficult to investigate in atomic glasses due to their low scattering signal and the numerous spurious effects that can affect the measurements, such as surface scattering, scattering from impurities and stress-driven relaxations. I will report here on how these effects can affect the measurements of the relaxation dynamics in a chalcogenide and a borate glass, and on the strategies that I have used to minimize their contribution both optimizing the experimental setup and using different data-analysis strategies.