Elasticity basics: Stress and strain tensors, tensor transformations, Mohr’s circle representation of stress and strain, constitutive equations. Origin of stresses in thin films: thermo-elastic mismatch between film and substrate, lattice mismatch in hetero-epitaxial films, recrystallization, phase transformation, incorporation of atoms and chemical reactions. Application of the above for designing structures with low stresses. Experimental techniques for measuring stresses/strains in thin films: Substrate curvature; Stoney’s equation, methods for curvature measurement and X-ray diffraction. Measurement of mechanical properties of thin films - nanoindentation, bulge test, 4-point bend test, and micro-tensile test. Models for high stresses, strain-hardening rates and Bauschinger effect in thin films, influence of grain size, film thickness and interfaces.
Texts / Reference Books:
- Marc André Meyers, Krishan Kumar Chawla, Cambridge,Mechanical Behavior of Materials
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