Brian Welk, Jacob Jensen, John Sosa, Dan Huber, Robert Williams, Babu Viswanathan, and Hamish L Fraser
Center for the Accelerated Maturation of Materials, Department of Materials Science and Engineering, The Ohio State University, 1305 Kinnear Road, Columbus, OH 43212, USA
The combination of x-ray energy dispersive spectroscopy (XEDS) and/or electron energy loss spectroscopy (EELS) with aberration-corrected (S)TEM has provided, in principle (tantalizingly!), the ability to determine the chemical composition of the atoms in specific atomic columns in thin foils. This has resulted in the publication of a number of reports of such determinations. However, there are a number of factors that work against the possibility of deducing accurate values for atomically-resolved compositional determinations. These include probe delocalization, spectral contributions from phonon-scattered electrons (cross-talk), beam convergence, radiation damage, and foil thickness. The influence of these various factors will be considered and an assessment made of the possibility of performing such compositional determinations. In these latter experiments, a “standard” sample is utilized, namely the B2 intermetallic compound Ni-50.4at.%Al, in which the compositions of atomic columns when viewing along <100> are known without ambiguity.
