This tutorial chapter provides a synopsis of the theoretical concepts needed for understanding
subsequent chapters. The concepts of engineering strain, true strain, Eulerian strain and in particular,
the tensor nature of strain are first introduced. The components of the stress tensor which give rise to
strain are next discussed. The three main elastic properties of solids namely: Young’s modulus, shear
modulus and Poisson’s ratio are defined. The piezoresistance effect introduced in the first chapter is
discussed quantitatively. This is followed by two topics on the optical properties of semiconductors, the
Kramers-Kronig relation and the optical joint density of states used in optical strain metrology.
Keywords: Strain, Stress, Tensor, Piezoresistivity, Dielectric function, Critical points.
