CDS&E: Resolving Nonlinearity in Thin Film Chemical Analysis: Roughening, Matrix Effects and Chemical Damage

University Of Texas At Dallas, Richardson TX

Investigators

Abstract

This project is funded by the Chemical Measurement and Imaging program of the Chemistry Division. Professors Lev Gelb and Amy Walker of the University of Texas at Dallas are improving methods for interpreting surface chemical analysis data. Many methods for studying a surface or thin film involve blasting it with high-energy beams of electrons or ions. These approaches provide information about the atoms and molecules present, but also cause unwanted chemical reactions and surface roughening. This team is developing easy-to-use analysis software to account for these "nonlinear" effects. The result is that the quality of surface chemical analysis data is improved, and this advances research in fields ranging from energy, to electronics, to advanced materials, to biotechnology. Graduate and undergraduate students are trained in the critically important fields of surface characterization, data analysis, numerical methods, and high-performance computing. This project focuses on two types of nonlinearity in chemical imaging: quantitative modeling of matrix effects in secondary ion mass spectrometry (SIMS) imaging of organic surfaces, and resolution of chemical damage and roughening in x-ray photoelectron spectroscopy (XPS) depth profiling of complex oxides. Extraction of sample properties in the presence of these nonlinearities is addressed through physical modeling within a Bayesian framework, which is made possible through a combination of theoretical developments, modern computing power, improvements in experimental protocols, and physical understanding of the underlying phenomena. In order to promote the use and further development of advanced data analysis in chemical imaging, software developed in this project is freely distributed and promoted as a community resource, along with online exercises that illustrate its use and application. SIMS and XPS are widely used in many areas, so improving the performance of these and related techniques is a significant long-term benefit to society at large.