Quantitative measurement of image intensity in transmission electron microscope images

Abstract

Quantitative high-resolution electron microscopy should be able to determine the positions and the types of the atoms at interfaces by the comparison of focal series of lattice images with image simulations. However, it has been found in the past that intensities in electron microscope images are poorly predicted by image simulations and in particular, high-resolution image contrast is often wrong by a factor of three or more. To find out why they do not match in HRTEM images, here focal series of images from cleaved Si and GaAs specimens are used to assess the degree of mismatch with image simulations, comparing image intensities from unfiltered and energy-filtered bright-field and dark-field image series at the <001> zone axis. The contrast of similar series of high-resolution images has also been investigated, both with and without an objective aperture. It is interesting that some of the biggest discrepancies with simulations occur at the lowest sample thicknesses. The implications for quantitative electron microscopy are discussed.