QUANTITATIVE-DETERMINATION OF DEFOCUS, THICKNESS AND COMPOSITION FROMHIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPY LATTICE IMAGES

A quantitative method for the direct determination of defocus Delta f, local thickness t and local composition x from high-resolution transm ission electron microscopy lattice images of wedge-shaped crystal samp les is proposed. The method relies on the analytically derived relatio n between the first-order linear and nonlinear image Fourier coefficie nts J(1) and J(2) on Delta f, t and x. By plotting J(1) vs J(2) for va rying t, ellipses with defocus- and composition-specific geometry are obtained. By reconstructing the appropriate ellipse for image regions of homogeneous composition, Delta f and t can be determined independen tly. At interfaces, local compositions,x can be determined within the full range 0 less than or equal to x less than or equal to 1 by utiliz ing systematic variations of the ellipse's geometry with varying x.