| AVS 60th International Symposium and Exhibition | |
| Synchrotron Analysis Focus Topic | Wednesday Sessions |
| Session SA+AS+MI+SS-WeM |
| Session: | Synchrotron and Imagery: PEEM, Nano-ARPES and Others (8:00-9:40 am)/Synchrotron TXRF and Related Techniques (10:40 am-12:00 pm) |
| Presenter: | D. Lützenkirchen-Hecht, Bergische Universität Wuppertal, Germany |
| Authors: | D. Lützenkirchen-Hecht, Bergische Universität Wuppertal, Germany J. Stötzel, Bergische Universität Wuppertal, Germany O. Müller, Bergische Universität Wuppertal, Germany R. Frahm, Bergische Universität Wuppertal, Germany |
| Correspondent: | Click to Email |
The surfaces of materials play a decisive role for many fundamental physico-chemical processes such as e.g. acqueous and gaseous corrosion, catalysis, or coating procedures. Many of those processes proceed in non-vacuum environments, so that classical surface analytical techniques like XPS or scanning electron microscopy are not suited for in-situ investigations. Furthermore, all of the above mentioned processes are strongly time dependent, so that fast surface sensitive in-situ probes are necessary to study the respective phenomena. EXAFS can be made surface sensitive by using the grazing incidence geometry: For incidence angles below the critical angle of total reflection, the penetration depth of the X-rays amounts to only some few nanometers, and the reflected X-ray beam only contains information about the near surface region of the studied samples. Here we have combined the grazing incidence geometry with the Quick-scanning EXAFS (QEXAFS) data collection. Recent experimental developments of QEXAFS have substantially improved the time resolution to about 50 ms for a single spectrum, thereby enabling completely new surface science experiments.
In this contribution, we will briefly discuss the experimental setup and present results obtained in-situ during the film deposition by sputtering. The growth of gold and copper thin films on float glass substrates and Si wafers were investigated as examples. We will show that the evolution of the film structure can be followed with a subsecond time resolution, and a detailed modelling of the experimental data using the distorted wave Born approximation yields e.g. the film composition, thickness and roughness as a function of time. First experiments showed the need for an automated analysis, and we will also introduce appropriate software solutions for the processing of huge amounts of data acquired in a typical time resolved experiment with several thousands of spectra. Furthermore, we will also discuss the oxidation of the Cu thin films by their exposure to ambient air at different temperatures. The results clearly show that the dynamics of the oxidation are strongly depending on the actual temperature of the samples.