Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 34: Metal Substrates: Structure, Epitaxy and Growth

O 34.6: Poster

Dienstag, 17. März 2015, 18:15–21:00, Poster A

Thermodynamics of Deposition Flux dependent Intrinsic Film Stress — Amirmehdi Saedi and •Marcel Rost — Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands

The growth of polycrystalline films at temperatures above ~0.2 of the melting temperature is accompanied by compressive stress development after film closure. Mysteriously, a significant part of this stress has a reversible nature: it disappears when the deposition is stopped and re-emerges upon resumption. It has been suggested that the variation of the surface chemical potential upon starting/stopping of the deposition may cause adatoms to diffuse in/out of the grain boundaries leading to the development/relaxation of the intrinsic compressive film stress. However, film growth involves a myriad of atomic processes such that the mystery is not yet solved and new mechanisms and ideas are still published frequently. Here we represent an analytical derivation, in which we address the variation of the chemical potential of the surface, the grain boundaries, and the film, that fully explains the magnitude of the reversible compressive stress using pure thermodynamic arguments. The tremendous stress levels observed in the experiments can indeed be explained by the flux induced density variations in the extremely dilute adatom gas on the surface.