QUANTITATIVE HIGH-SPEED MATCHING OF HIGH-RESOLUTION ELECTRON-MICROSCOPY IMAGES

A procedure has been developed which allows the sample thickness and the defocus value of high-resolution electron microscopy micrographs to be determined. The cross-correlation coefficients between an experimental input image of a crystalline specimen and a large number of simulated images covering the whole defocus-thickness plane are evaluated in Fourier space. The result of this defocus-thickness scan is displayed by means of a cross-correlation map. Using a through-focus series of the ordered alloy Ni4Mo as an example, it is demonstrated that an unambiguous determination of the experimental parameters on a local level within a micrograph is possible. Moreover, if simulated images are used as input instead of experimental images, the cross-correlation method allows a simple and effective calculation of maps displaying the occurrence of certain image types of special interest in the defocus-thickness plane.