Mass-Thickness Measurements in the Transmission Electron Microscope: A Single-Standard Approach to Quantitative EDS Analysis.

Abstract

Quantitative compositional analysis with energy-dispersive X-ray spectroscopy (EDS) in the scanning transmission electron microscope (STEM) is an important tool for materials science. Here, we test a single-standard approach to quantitative EDS on focused ion beam (FIB) sections of SrTiO3, CaTiO3, and Fe sulfides. We confirm previous reports that shadowing of X-rays is an important factor to consider in robust quantitative analysis and should be mapped out to optimize signal collection. Our data show that the orientation of the half grids used in FIB sample preparation can be adjusted in the transmission electron microscope sample holder to provide optimum line-of-sight from the sample to the EDS detector, minimizing X-ray occlusion. A precision of 2% can be achieved when comparing EDS data in the STEM to quantitative wavelength-dispersive spectrometry in the electron microprobe. These results yield accuracies within 5% of stoichiometric composition for an optimized analytical geometry.