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Electron microscopy is a powerful tool for directly visualising structure and with the advent of aberration correction, atomic columns and even individual atoms are now routinely imaged. HAADF STEM offers a great sensitivity to atomic number - the well known Z-dependence in the measured intensity. By calibrating the HAADF detector, putting images on an absolute scale, and using an absolute HAADF scattering cross section comparison, it is possible to compare experiment with simulations in a parameter robust manner. We show how the cross section method relieves the use of a fitting parameter for the probe and is insensitive to experimental parameters such as defocus. Finally, we test our analysis method using a 2-dimensional nano-structure to identify the composition of atomic columns in thin layered materials. We also discuss some of the potential sources of error in quantifying small, thin, low-scattering and beam sensitive samples.

Core-shell structured heterogeneous catalyst nano-particles offer the promise of more efficient precious metal usage and also novel functionalities but are as yet poorly characterised due to large compositional variations over short ranges. High angle annular dark field detector in a scanning transmission electron microscope is frequently used to image at high resolution because of its Z-contrast and incoherent imaging process, but generally little attention is paid to quantification. Energy dispersive X-ray analysis provides information on thickness and chemical composition and, used in conjunction with HAADF-STEM, aids interpretation of imaged nano-particles. We present important calibrations and initial data for truly quantitative high resolution analysis. © 2010 IOP Publishing Ltd.