Monday, October 22, 2012

Nanometer-scale, quantitative composition mappings of InGaN layers from a combination of scanning transmission electron microscopy and energy dispersive x-ray spectroscopy

K Pantzas, G Patriarche, D Troadec, S Gautier, T Moudakir, S Suresh, L Largeau, O Mauguin, P L Voss and A Ougazzaden



Using elastic scattering theory we show that a small set of energy dispersive x-ray spectroscopy (EDX) measurements is sufficient to experimentally evaluate the scattering function of electrons in high-angle annular dark field scanning transmission microscopy (HAADF-STEM). We then demonstrate how to use this function to transform qualitative HAADF-STEM images of InGaN layers into precise, quantitative chemical maps of the indium composition. The maps obtained in this way combine the resolution of HAADF-STEM and the chemical precision of EDX. We illustrate the potential of such chemical maps by using them to investigate nanometer-scale fluctuations in the indium composition and their impact on the growth of epitaxial InGaN layers.



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