QUANTITATIVE-ANALYSIS OF STRAIN FIELD IN THIN-FILMS FROM HRTEM MICROGRAPHS

A method for measuring and mapping displacement fields and strain fiel ds has been developed. It is based on the Fourier analysis of a HRTEM lattice image selecting a strong Bragg reflection and performing an in verse Fourier transform. The phase component of the resulting complex image gives information on local displacements of atomic planes. The t wo-dimensional (2D) displacement field can then be derived by applying the method to two non-collinear Fourier components. Local strain tens or components epsilon(xx)((r) over bar), epsilon(yy)((r) over bar), ep silon(xy)((r) over bar) and epsilon(yx)((r) over bar) can be obtained by analysing the derivative of the displacement field. Applied to HRTE M images of thin films, this technique gives quantitative information on the variations of the strain relaxations in the different layers. T he method is illustrated studying a fully relaxed GaSb/GaAs interface. (C) 1998 Elsevier Science S.A.