LAUSR

The most widespread APT data reconstruction method was first proposed in 1995 [1]. Incremental changes to the method have lead to improved accuracies as datasets became larger, laser field evaporation became more widespread, and heterogeneous materials systems became more commonplace. Unfortunately, errors during APT data reconstruction are still limiting widespread acceptance of APT as a quantitative imaging technique. There are many factors contributing to these inaccuracies, but they can include inaccurate estimation of specimen geometry based upon the assumed evaporation field, inaccurate assumptions of the ion trajectories, and magnification changes due to varying field evaporation characteristics at heterointerfaces. Utilizing ex-situ correlative TEM imaging with APT has been shown to improve the accuracy of data reconstruction through the quantification of many of the reconstruction variables, including radius, shank angle, atomic spacing, detection efficiency, image compression factor, and field of view [2]. However, the full use of TEM has not yet been applied to the APT experiment as a wealth of other information are useful and readily attainable. Our group has previously engineered a UHV electron microscope on to an existing commercial APT instrument [3], however, the imaging performance was not of high enough spatial resolution to allow for reconstruction improvements. Therefore, in order to further improve APT as a quantitative imaging and analysis technique, hardware enabling in-situ APT within a TEM objective lens is needed [4].