Solvent vapor annealing of stable glasses*

Stable glasses (SG) are highly dense, low energy glasses that are made by physical vapor deposition (PVD). Because of their desirable properties and wide range of applications, they are extensively studied glasses. However, measuring their dynamics can be difficult since they are produced directly into a SG state on a substrate during the process of PVD. We have introduced a novel and indirect method of measuring the dynamics of SG using solvent vapor annealing (SVA). Using this technique, together with in-situ ellipsometry, we have shown that even at low solvent vapor pressure, the surface of SG swells more quickly, in an analogous Fickian type diffusion, compared to that of the bulk. Above a certain threshold of vapor pressure, the bulk of the film swells linearly with time, which demonstrates a Case II type of diffusion. This shows the diffusion of the solvent molecule through the film is limited by the relaxation of the molecules such that the solvent uptake is governed by a two-layer model; one swollen with solvent and the other the dry medium. By monitoring the solvent front moving across the film, we compare the dynamics of the SG films of different stability produced at different deposition temperatures.