Reference-free evaluation of thin films mass thickness and composition through energy dispersive x-ray spectroscopy

TL;DR

This paper introduces a novel reference-free method for evaluating thin film mass thickness and composition using energy dispersive X-ray spectroscopy, leveraging theoretical calculations of X-ray generation in multilayer samples.

Contribution

The paper develops a new electron transport model-based method that accurately measures thin film properties without reference samples or multiple voltage scans.

Findings

Mass thickness accuracy around 10 μg/cm²

Validated against standard techniques

Able to profile nanostructured, high-roughness films

Abstract

In this paper we report the development of a new method for the evaluation of thin films mass thickness and composition based on the Energy Dispersive X-Ray Spectroscopy (EDS). The method exploits the theoretical calculation of the in-depth characteristic X-ray generation distribution function, $\phi$/($\rho$ z), in multilayer samples, obtained by the numerical solution of the electron transport equation, to achieve reliable measurements without the need of a reference sample and multiple voltages acquisitions. The electron transport model is derived from the Boltzmann transport equation and it exploits the most updated and reliable physical parameters in order to obtain an accurate description of the phenomenon. The method for the calculation of film mass thickness and composition is validated with benchmarks from standard techniques. In addition, a model uncertainty and sensitivity analysis is carried out and it indicates that the mass thickness accuracy is in the order of 10 $\mu$g/cm$^2$, which is comparable to the nuclear standard techniques resolution. We show the technique peculiarities in one example measurement: two-dimensional mass thickness and composition profiles are obtained for a ultra-low density, high roughness, nanostructured film.