Combining STEM and APT: How Correlative Electron Microscopy and Diffraction Can Help Us on the Road to Atomic Scale Tomography

Atom Probe Tomography is widely known to be one of the leading atomic scale characterization techniques, as evidenced by sub-nanometer scale 3-D (tomographic) imaging with 10 ppm chemical sensitivity.  Unfortunately, the technique can suffer from gross inaccuracies when it comes to tomographic data reconstruction.  Traditional reconstruction techniques are geometric in nature and require a-priori knowledge of the material; specifically, its atomic evaporation field as a function of temperature, visible light absorption and thermal diffusivity, or the specimen geometry must be known.  As will be demonstrated in this talk, these traditional reconstruction techniques can be greatly improved by electron microscopy imaging and diffraction.  Quantitative information can be gathered on the specimen geometry before and after APT analysis, thus allowing for the photon cross section, thermal conductivity, electric field, and image compression factor, and sphere to cone ratio to also be calculated.  Using electron diffraction, the atomic spacing can be determined quantitatively, and thus the detector efficiency, field of view, and atomic volumes can be input into the reconstruction algorithm.  Fortunately, electron diffraction also opens up the possibility for new reconstruction paradigms, which will also be detailed.  An in-situ STEM / APT instrument engineered (sometimes violently) and constructed at CSM will be detailed.

Dr. Brian P. Gorman

Associate Professor

Colorado Center for Advanced Ceramics

Metallurgical and Materials Engineering

Colorado School of Mines

1500 Illinois St, Golden, CO 80401

USA

 

Phone +1 303 384 2239 E-Mail Assoc. Prof. Dr. Brian P. Gorman Colorado School of Mines, Brian P. Gorman