Scanning Microscopy


In addition to several new predictions, the general theory of thermodynamic stability of heterogeneous systems with rearrangement has allowed us to understand the roots of several experimental and theoretical results of the past. One of them is an outstanding paper of Asaro and Tiller on stress corrosion cracking by surface diffusion published two decades ago. We compare results of Asaro and Tiller with conclusions of thermodynamic theory of solids with rearrangement and develop some Asaro-Tiller results in the directions dictated by the needs of thin films technology and experiment. A surface diffusion model in a prestressed elastic solid is studied on the basis of the Onsager approach of irreversible thermodynamics. The master system governing a quasi-static evolution of the surface corrugations is derived in the framework of nonlinear elasticity and for the model of a surface energy incorporating both the Laplace excess pressure under curved interface and the Herring curvature term in the local chemical potential. Then, we derive a dispersion relation of the growth rate of two-dimensional infinitesimal corrugations atop an isotropic uniformly stressed elastic layer clamped to a substrate. The relation predicts different patterns of surface morphology produced by the fastest unstable corrugations. The patterning which develops depends on the applied stresses, thickness and material parameters of the layer and substrate.

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