Now published in SCIENCE, this method represents a key building block in the development of organic semiconductor elements. Supported by the Austrian Science Fund FWF, the success of this project rested on the mathematical transformation of the measured data.
This made it possible to interpret the distribution of the electrons and draw conclusions about the potential properties of organic semiconductor elements.
Ultra-thin films made of organic molecules form the basis of future semiconductor technologies. Because organic molecules are extremely flexible, they can be used in a whole new range of applications, making it equally possible to create pliable screens and cost-effective solar cells. However, apart from these everyday applications for organic semiconductors, the most important task is to gain a better understanding of the interactions between organic materials and inorganic carrier substances. A team from the Universities of Graz and Leoben has now succeeded in developing a means of doing just that.
The team's achievement is based on the use of the photoelectric effect. This enables individual electrons to be "knocked out" of organic molecules. As part of this project, an organic molecule was exposed to ultraviolet light that emitted sufficient energy to separate individual electrons from the molecules. The direction and speed of the electrons thus released were then measured using highly-sensitive detectors, generating the basic data required to calculate the electron distribution within the molecule. As part of this process, Prof. Michael Ramsay and his team from the University of Graz used a hexaphenyl film just one molecule thick that had been applied to a copper surface. The team from Graz carried out the actual measurements at the Berliner Elektronen-Speicherring Gesellschaft für Synchrotronstrahlung (BESSY, Berlin Electron Storage Ring Society for Synchrotron Radiation).A CALCULATED RESULT
This new method is particularly valuable as it means measuring the behaviour of electrons at the interfaces between organic semiconductors and metals is now relatively easy and highly accurate. The study "Interface controlled and functionalised organic thin films" supported by the FWF as part of the National Research Network (NFN) is thus making a fundamental contribution to future applications of organic semiconductors.
Original publication: Reconstruction of Molecular Orbital Densities from Photoemission Data, P. Puschnig, S. Berkebile, A. J. Fleming, G. Koller, K. Emtsev, T. Seyller, J. D. Riley, C. AmbroschDraxl, F. P. Netzer, M. G. Ramsey: Science 326, 702 (2009).Scientific Contact:
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