Automating ALCHEMI at the nano-scale using software compatible with PC-controlled transmission electron microscopy.

Abstract

Atom location by channeling-enhanced microanalysis (ALCHEMI) is a technique to obtain atom-site-specific information on constituent elements in a crystalline sample by acquiring a set of core electron transition spectra while tilting the incident beam. This methodology has been extended to a more quantitative technique called high-angular-resolution electron-channeled X-ray/electron spectroscopy (HARECXS/HARECES). There is a growing demand for analyzing smaller areas, such as small particles and multilayers. However, the minimum size of a region of interest probed by the present hardware-assisted automated HARECXS/HARECES scheme is limited to no smaller than 1 µm, not only by the size of the electron probe and its convergence angle but also by the movement of the probe position associated with the beam tilt due to aberrations of the hardware system. Herein, QED (quantitative electron diffraction), a commercial plug-in working on an integrated software platform, Gatan Microscopy Suite, was modified to enable the calibration and control of the probe to resolve the aforementioned limitation. In addition, a more sophisticated scheme for QED was developed to realize the ALCHEMI method for energy-dispersive X-ray spectroscopy, electron energy-loss spectroscopy or both concurrently. This allows access to ALCHEMI and its derivative methods, automatically executed with any type of current PC-controlled commercial microscope on an area as small as 30 nm, without modifying the hardware system.