| AVS 59th Annual International Symposium and Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoM |
| Session: | Quantitative Surface Chemical Analysis, Technique Development, and Data Interpretation - Part 1 |
| Presenter: | S. Tougaard, University of Southern Denmark |
| Correspondent: | Click to Email |
This is a brief summary of the work that was involved in the development of the technique for quantitative XPS from analysis of the background of inelastically scattered electrons. About 30 years ago it became evident that these electrons must carry valuable information about the depth where the XPS electrons are excited. Theoretical modeling started and algorithms were developed. It was necessary to have an accurate description of the electron energy loss processes which at that time was not available. Theoretical calculations of inelastic cross sections based on a dielectric response description were done and a new experimental method to determine this from analysis of reflected electron energy loss spectra (REELS) was also developed.
To make these procedures for quantitative XPS analysis work in practice it is however not possible to use calculations valid only for specific sample compositions. Therefore an effort was made early on to find cross sections which can be used as an approximation for wide classes of materials and compositions. This resulted in the Universal cross sections which are now widely used and without which practical use of the formalism would have been very limited. The resulting XPS analysis technique was summarized in [1].
In the following years, much effort was then centered on applications to increasingly finer details of the morphology of nanostructures. This requires a careful data analysis since otherwise the uncertainty on the determined morphology may be large. Sometimes the detailed morphology is however not the most important issue for technological applications. Things like speed of analysis, robustness, and automation is often more important in industrial environments. It was therefore decided to develop a simpler algorithm which does not give as detailed information but which is very robust and therefore faster to use and less dependent on a meticulous analysis procedure. The resulting algorithm [2] has been shown to be very robust and therefore suitable for automation. It proved also effective in generating 3D images of nano-structures where automation is mandatory since thousands of spectra (one per pixel) must be analyzed.
Throughout, efforts were always exerted to test the validity of each step in the development of algorithms and procedures by designing and performing critical experiments. This is of utmost importance to ensure progress which does not lead to dead ends.
In this talk I will give an overview of the development of the technique and discuss some technological applications.
1. S. Tougaard, J. Vac. Sci. Technol. A14, 1415 (1996)
2. S. Tougaard, J. Vac. Sci. Technol. A23, 741 (2005)