Monitoring the Kinetic stability of vapor-deposited glasses using in-situ solvent vapor annealing.

Stable glasses (SGs), prepared by physical vapor deposition have been shown to have improved density and thermal stability analogous to highly aged liquid quenched glasses. Numerous studies have investigated their thermodynamic stability via measurements of density, enthalpy, and fictive temperature. However, the kinetic stability of SG films is difficult to evaluate, as the SG transformation mechanism upon heating above the glass temperature can depend on film thickness and the transformation temperature. Here, we employ an indirect method of measuring the kinetic stability of SG films using in situ solvent vapor annealing (SVA) combined with in situ spectroscopic ellipsometry. Under proper solvent vapor pressure, a moving solvent front is observed that starts from the free surface towards the center of the film, analogous to the thermal annealing front. Using this technique we study the kinetic stability of films of various molecules, deposited across a range of temperatures and thicknesses, through measurements of the solvent front velocity. In contrast to thermal annealing fronts, SVA can be applied to both liquid quenched and SGs with a broad range of stability, providing a direct comparison in these systems.