Elastic analysis of interfaces in solids.

Abstract

Interfaces between dissimilar materials and within polycrystalline materials are ubiquitous in modern materials. Characteristics of these interfaces commonly control the overall properties of complex materials. In this thesis, I examine several consequences of the elastic nature of interfaces. Three specific problems are examined in which macroscopic and microscopic aspects of interfaces are elucidated. <italic>Elastic analysis of dislocations at interfaces</italic>. We employ a linear model of interfacial bonding and continuum elastic analysis to study dislocations near a heterophase interface. We present a simple method for determining elastic fields in such bimaterials originating from internal sources of stress (such as dislocations). Using this method, we determine forces acting on dislocations as a function of the dislocation-interface separation, the strength of the bonding at the interface and the properties of the bounding materials. <italic>Morphology evolution during multilayer film growth </italic>. The stability of multilayer thin films during growth is analyzed. The evolution of the growing film is controlled by diffusion along the growth surface. The nature and extent of the surface diffusion is controlled by the interplay between surface tension, the elastic strain energy arising from misfit, and the morphology of both the growing surface and buried interfaces. We find that multilayer film growth can be stabilized by appropriate choice of material parameters and growth conditions. Conditions for unstable growth and the nature of the resultant morphological instability are predicted. <italic>Elastic models of surface defects</italic>. We employ elastic analysis and atomistic computer simulations to study the interactions between defects (surface steps, adsorbed atoms) on solid surfaces. The simulations data are analyzed in terms of a 'dipole' model in which the defect is replaced by a surface force couple. We find that the dipole model provides a good description of interactions between two surface steps and between two adsorbed atoms and a satisfactory description of interactions between a step and an adatom. For the interaction between two adsorbed atoms we emphasize the importance of anisotropy in the treatment of surface defects.