Measurement of displacement and strain by high-resolution transmission electron microscopy

The measurement of strain using high-resolution electron microscopy (HREM) is presented. In particular, the geometric phase technique for measuring the distortion of lattice fringes in the image is described in detail. The method is based on the calculation of the "local" Fourier components of the HREM image by filtering in Fourier space. The accuracy and inherent limitations of strain mapping will be discussed, such as image distortions, the projection problem and thin film effects. Examples are given where displacements are measured to an accuracy of 0.003 nm at nanometre resolution, strain variations to within 1%, and rotations to within 0.2degrees. Applications to the study of compositional variations in strained InxGa1-xAs islands grown on GaAs, relaxation of La0.67Sr0.33MnO3/SrTiO3 heterostructures, and misfit dislocation networks in thin epitaxially grown layers will be presented.