Date of Graduation
Eberly College of Arts and Sciences
Physics and Astronomy
Coarsening processes play prominent roles in non-equilibrium statistical physics and in applied physical sciences. A new area in this field of statistical physics has emerged from recent experimental revelations that long range de-wetting forces acting across thin films, such as the fundamental van der Waals interactions, may drive the formation of large clusters (tall multi-layer islands) and pits, observed in thin films of soft materials (polymers), as well as in thin films of liquid and solid metals. Motivated by the experiments, in this Thesis we elucidate the fundamentals of the non-equilibrium statistical mechanics of solid thin films coarsening within a unified model explicitly incorporating de-wetting interactions. By analytic arguments and simulations of the model, we study the growth laws of clusters formed in thin films due to the de-wetting interactions. The ultimate long time-scale cluster growth coarsening exponents are found to depend on the substrate dimensionality, unlike the super-universal exponents encountered in standard coarsening phenomena. Nonetheless, the ultimate cluster growth scaling laws at long times are strongly universal: Short and long range de-wetting interactions yield the same coarsening exponents. However, long range de-wetting interactions, such as the common van der Waals forces, introduce a distinct long lasting early-time scaling behavior characterized by a slow growth of the cluster height/lateral size aspect ratio (i.e., a time-dependent Young angle), and by effective coarsening exponents that depend on cluster size. In this thesis, we develop a theory capable to calculate these effective size-dependent coarsening exponents characterizing the cluster growth in the early-time cross-over regime. Such a pronounced crossover behavior has been indeed seen in experiments; however its physical origin has remained elusive to this date. Our results attribute these observed phenomena to ubiquitous long range dewetting interactions acting across thin films.
Constantinescu, Adi, "Cluster Growth During De-Wetting of Solid Thin Films: Coarsening Exponents and the Role of Long Range De-Wetting Interactions" (2011). Graduate Theses, Dissertations, and Problem Reports. 3460.