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

该项目由化学部的化学测量和成像计划资助。达拉斯得克萨斯大学的列夫·盖尔布和艾米·沃克教授正在改进解释表面化学分析数据的方法。研究表面或薄膜的许多方法包括用高能电子束或离子束对其进行轰击。这些方法提供了有关存在的原子和分子的信息，但也会导致不必要的化学反应和表面粗糙。这个团队正在开发简单易用的分析软件来解释这些“非线性”效应。结果是，表面化学分析数据的质量得到了提高，这促进了从能源、电子、先进材料到生物技术等领域的研究。研究生和本科生在表面表征、数据分析、数值方法和高性能计算等关键领域接受培训。本项目主要研究化学成像中的两种类型的非线性：有机表面二次离子质谱仪成像中基质效应的定量模拟，以及复杂氧化物X射线光电子能谱深度剖析中化学损伤和粗化的解决。在存在这些非线性的情况下，样本属性的提取是通过贝叶斯框架内的物理建模来解决的，这是通过理论发展、现代计算能力、实验方案的改进以及对潜在现象的物理理解的组合来实现的。为了促进先进数据分析在化学成像中的使用和进一步发展，本项目开发的软件作为社区资源免费分发和推广，以及说明其使用和应用的在线练习。SIMS和XPS被广泛应用于许多领域，因此，提高这些技术和相关技术的性能对整个社会来说是一个重大的长期利益。

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.