Since more than 20 years a variety of scientists working in different fields ranging from fundamental physics, material science, crystal and film growth, device fabrication and engineering, are puzzled by the emergence of a mysterious internal stress during the growth of polycrystalline films:
When the deposition is started, stress levels higher than the yield strength of the material have been observed to emerge in a matter of seconds. Astonishingly, a significant part of this stress is found to be reversible: i.e. it fully vanishes when the deposition is stopped/interrupted!
After two decades of investigation, the origin of this phenomenon is still not yet clear. The reason for this is that even the most simple film deposition model involves a myriad of interlinked surface and bulk phenomena, ranging from the atomic to the macroscopic scale. Due to this complication, so far at least six different phenomenological models have been proposed. However, all of these models fail to address the origin at its fundamental level, as the predictions of each of these models contradict at least one experimental observation. In this sense, the growing number of the proposed mechanisms has practically resulted in more ambiguity and disagreement rather than in clarity and consensus.
We are focusing both on a proper thermodynamical description and on the real-time experiments, in which we not only follow the deposition on an atomic scale during the growth, but simultaneously also measure the internal film stress!
The thermodynamic description can be found here.