Rapid etching X-rayed: Physicists unveil processes during fast chemical dissolution

A breakthrough in the study of chemical reactions during etching and coating of materials was achieved by a research group headed by Kiel physicist, Professor Olaf Magnussen. The team from the Christian-Albrechts-Universität zu Kiel (CAU), Germany, in collaboration with staff from the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, have uncovered for the first time just what happens in manufacturing processes, used for the formation of metal contacts thinner than a human hair in modern consumer electronics, such as flat-screen television.

The results appear in the Journal of the American Chemical Society.

For their research the scientists used the intense X-ray radiation of the experimental station ID32, one of the ESRF's instruments. The X-ray beam was directed onto a gold surface while it dissolved in diluted hydrochloric acid. Because the reflected X-rays are sensitive to tiny changes in the atomic arrangement at the material's surface, the metal removal during the reaction can be precisely measured.

"Such studies were only possible during very slow changes of the material so far," Olaf Magnussen explains. To gain insight into the fast reactions going on in industrially employed processes the speed of the measurements had to be increased more than a hundredfold. Even during very fast etching the removal of the metal proceeded very uniformly. "The material dissolves quasi atomic layer by atomic layer, without formation of deeper holes," Magnussen remarks. In a similar way, the team could follow the attachment of atoms during the chemical coating of materials.

Among the diverse industrial applications of chemical etching and coating are high-tech manufacturing processes, for example in the production of electronic devices. These require precisely controlled reactions. In order to optimize such etching and coating processes they are intensely studied worldwide. Until now it was only possible to analyse the finished product. With the method developed by the scientists, changes within a few thousandth seconds may be detected so that the reactions at the material's surface can be tracked on the atomic scale under realistic conditions.

Christian-Albrechts-Universität zu Kiel is a North German research university with proven international expertise in the field of nanoscience, including research using synchrotron radiation. In a number of research networks, funded by the German Federal Ministry of Education and Research, Kiel scientists develop new methods and instruments. In addition, the CAU competes for a Cluster of Excellence in the area of nanoscience and surface science within the ongoing round of the German Excellence Initiative.

The ESRF is a European research institution, funded by 19 nations, providing and utilizing brilliant synchrotron X-rays for advanced scientific research.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Christian-Albrechts-Universitaet zu Kiel.

Journal Reference:

Frederik Golks, Klaus Krug, Yvonne Gru¨nder, Jo¨rg Zegenhagen, Jochim Stettner, Olaf M. Magnussen. High-Speed in situ Surface X-ray Diffraction Studies of the Electrochemical Dissolution of Au(001). Journal of the American Chemical Society, 2011; 133 (11): 3772 DOI: 10.1021/ja1115748

Residual dipolar couplings unveil structure of small molecules

 German chemists at the Technische Universitaet Muenchen and the Karlsruhe Institute of Technology introduced a new method for identifying chemical compounds. The approach they used is an improvement on nuclear magnetic resonance measurements -- for decades one of the most successful methods for determining the chemical structure of organic molecules. The results now published in the scientific journal Angewandte Chemie show a handy approach to structural data when classical methods of analysis fail.

The team of Professor Burkhard Luy from KIT and Junior Professor Stefan F. Kirsch from the TUM has now shown for the first time that certain NMR parameters, the so-called residual dipolar couplings (RDCs), can make a significant contribution towards determining the constitution of chemical compounds when traditional methods fail. To do this they embedded molecules of the compound in a gel which slightly constricts their mobility. By stretching the gel, the molecules can be aligned along a preferred orientation. While residual dipolar couplings average out in solution, they become measurable in such partially aligned samples and provide valuable structural information that can be used to build a model of the molecule.

To test this new approach to chemical structure determination the scientists examined a molecule whose atomic composition was known, but not the precise connectivities of the individual atoms in the molecule. The molecule was obtained using a unique reaction, so there were no precedents for its structure. Classical methods of analysis failed because of the compactness of the molecule. In this particular case it was only possible to determine the structure by means of residual dipolar couplings, so that the newly acquired knowledge could be used to draw conclusions about the formation of the molecule – something that in the past could only be speculated about.

"This type of analysis will not be suitable for all structures in the future," said scientists Luy and Kirsch. "There will still be molecules whose structures will defy all attempts at unraveling, in spite of tremendous efforts and cutting-edge technologies. But this new method provides us with one further tool to help us unravel the structural mysteries of nature."

More information: Grit Kummerlöwe, Benedikt Crone; Manuel Kretschmer, Stefan F. Kirsch und Burkhard Luy: Residual Dipolar Couplings as a Powerful Tool for Constitutional Analysis: The Unexpected Formation of Tricyclic Compounds. Angewandte Chemie International Edition, scheduled to go online 17 or 18 February 2011. DOI:10.1002/anie.2010007305

Provided by Technische Universitaet Muenchen