title: Structural origin of fragility in Ge-As-S glasses investigated by calorimetry and Raman spectroscopy.
abstract: The fragility index (m) of a series of Ge-As-S glasses covering a wide range of mean coordination (⟨r⟩) and stoichiometry is measured by differential scanning calorimetry. The evolution of the fragility index appears to be better predicted by the stoichiometry than the mean coordination, and m shows a well-defined dependence on the departure from stoichiometry quantified as the at. % excess or deficiency in sulfur. The effect of stoichiometry on the fragility of Ge-As-S glasses is very similar to that observed in the Ge-As-Se system. A systematic Raman spectroscopy investigation also indicates the presence of large fractions of molecular species such as S8, As4S4, and As4S3 in the structure of some glasses. The presence of molecular species is shown to increase the fragility and decrease the glass transition temperature (Tg). These results emphasize that short-range order rather than long-range characteristics such as structural rigidity appears to control the fragility of chalcogenide glasses.
authors: †Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China.
authors: Yan
authors: Y
authors: Yang
authors: †Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China.
authors: Bin
authors: B
authors: Zhang
authors: †Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China.
authors: Anping
authors: A
authors: Yang
authors: †Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116, China.
authors: Zhiyong
authors: Z
authors: Yang
authors: ‡Department of Materials Science and Engineering, University of Arizona, Tucson, Arizona 85712, United States.
authors: Pierre
authors: P
authors: Lucas