Crystal Growth Kinetics of GeSe2 Polymorphs in Bulk Glasses and Thin Films: Role of Self-Diffusion and Viscosity

The knowledge of transport properties (viscosity and self-diffusion) and the knowledge of crystal growth of different polymorphs in amorphous materials prepared in different forms provide important information for the preparation, processing, and utilization of these materials. This article is the first study of the direct observation of crystal growth rates in amorphous GeSe₂ bulk samples and thin films. The study contains a detailed analysis of viscosity and crystal growth in amorphous GeSe₂ samples (bulks and thin films), revealing also information about the self-diffusion process. Two polymorphs of GeSe₂ crystals (low temperature─LT, and high temperature─HT) grew in GeSe₂ bulk glasses. In the thermal evaporated film, only LT-GeSe₂ was found. Nevertheless, the crystals in thin films grew far below the glass transition temperature. To properly analyze and describe the crystal growth kinetics, viscosity data were obtained using a thermomechanical analyzer and a nanoindentation system. A combination of crystal growth data and viscosities provides information about the size and transport speed (self-diffusion) of structural units incorporated into the GeSe₂ crystals.

This work investigates the viscosity, diffusion, and crystal growth rates in bulk and thin film samples of GeSe₂ amorphous glass. The connection between measured data offers key insights into crystal growth dynamics and self-diffusion processes within the studied materials. The relation between crystal growth rates and self-diffusion coefficients in GeSe₂ shows significant similarity to that observed in molecular systems.