Study of structural evolution during controlled degradation of ultrathin polymer films

Abstract

The structural aspects of polyacrylamide thin films annealed at degradation threshold temperature have been studied as a function of annealing time using in situ X-ray reflectivity technique in vacuum. We observe significant decrease of thickness and increase of density with annealing time for all the films. The dynamical behavior of the changes was modeled in terms of two distinct exponential decay functions, following our earlier observation of two different time scales for the chemical modification pathways, and was found to be in excellent agreement with the data. The diffusion coefficients of the polymer chains corresponding to the two modes are found to be different by an order of magnitude. It was found that the two dynamical modes correspond to the formation of two degradation products at two different rates. The larger time constants for both the modes in case of thickness reduction compare to the chemical changes was explained in terms of inter-chain entanglement and attachment of the polymer with the substrate.

Evolution of magnetic and structural properties of MgO thin film with vacuum annealing

“…One may note that annealing till 623 K, results in shift of critical angle to higher value relative to as-deposited specimen indicating an increase of electron density and hence mass density. The concurrent increase of mass density and reduction in film thickness with the vacuum annealing has also been reported in previous studies [16,17]. However, with further increase in annealing temperature at 823 K, critical angle shifts to lower value.…”