Observation of Collective Molecular Dynamics in a Chalcogenide Glass: Results from X-ray Photon Correlation Spectroscopy

The structural relaxation processes in a Ge3As52S45 molecular chalcogenide glass sample were directly studied by X-ray photon correlation spectroscopy (XPCS). XPCS was conducted at the first sharp diffraction peak at q = 1.16 angstrom(-1) at temperatures ranging from 123 K to above the glass transition at 328 K, and the results showed two different dynamical regimes. At a low temperature, the observed glass dynamics are slow and dominated by X-ray-photon-induced effects, which are temperature independent. At a higher temperature, we observed a dramatic decrease in the fluctuation timescales, indicating that the dynamics were mainly due to the intermolecular correlation of the As4S3 molecule in the glass. The timescales in this high-temperature range agree well with those determined from measurements of the Newtonian viscosity. Our XPCS studies suggest an extended length scale of the relaxation process in glassy Ge3As52S45 from the single molecule to the intermolecular range across the glass transition, providing a unique direct probe of the dynamics beyond the length scales of the individual molecule.

Automated summary

This study directly investigates the structural relaxation processes in a molecular chalcogenide glass sample using X-ray photon correlation spectroscopy (XPCS). Two different dynamical regimes were observed: slow dynamics dominated by X-ray-photon-induced effects at low temperatures, and dynamics primarily attributed to the intermolecular correlation of molecules at high temperatures. The length scales of the relaxation process in the glass were found to extend beyond the individual molecule, providing valuable insights into the dynamics of glassy materials.