Numerical modeling of specimen geometry for quantitative energy dispersive X-ray spectroscopy

TL;DR

This paper presents a numerical 3D model to understand how specimen geometry affects quantitative EDS measurements in TEM, highlighting the benefits of multiple detectors and providing methods to reduce shape-induced errors.

Contribution

A novel 3D modeling approach for specimen geometry's impact on EDS quantification, including strategies to mitigate shape-related uncertainties.

Findings

Complex geometries cause significant quantification uncertainty with single detectors.

Multiple symmetrically placed detectors reduce shape-induced errors.

The model accurately predicts asymmetric X-ray counts based on tilt.

Abstract

Transmission electron microscopy specimens typically exhibit local distortion at thin foil edges, which can influence the absorption of X-rays for quantitative energy dispersive X-ray spectroscopy (EDS). Here, we report a numerical, three-dimensional approach to model the geometry of general specimens and its influence on quantification when using single and multiple detector configurations. As a function of specimen tilt, we show that the model correctly predicts the asymmetric nature of X-ray counts and ratios. When using a single detector, we show that complex specimen geometries can introduce significant uncertainty in EDS quantification. Further, we show that this uncertainty can be largely negated by collection with multiple detectors placed symmetrically about the sample such as the FEI Super-X. Finally, based on guidance provided by the model, we propose methods to reduce quantification error introduced by the sample shape. The source code is available at https://github.com/subangstrom/superAngle.