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CeNS Colloquium

Place: Kleiner Physik-Hörsaal, Geschwister-Scholl-Platz
Date: 30.04.10, Time: 15:30 h

STM Manipulation of Charge, Spin, and Conformation of Atoms and Molecules

Prof. Saw-W. Hla
Physics & Astronomy Department, Ohio University

Scanning tunneling microscope (STM) manipulation of single atoms and molecules on surfaces allow construction of novel quantum structures on an atom-by-atom basis and demonstration of single molecule switches/devices on a one molecule at-a-time basis. STM is not only an instrument used to see individual atoms by means of imaging, but also a tool used to touch and take atoms/molecules or to hear their vibration by manipulations. Therefore, STM can be considered as the eyes, hands and ears of the scientists connecting our macroscopic world to the atomic and nanoscopic world. In our research projects, we combine a variety of STM manipulation schemes with tunneling spectroscopy techniques to investigate properties of atoms/molecules on surfaces [1]. This talk will include our recent results and achievements; in spintronic research area, we will demonstrate that not only manipulation of magnetic atoms can be done but also imaging of their spin directions is possible by using a magnetic STM tip [2]. In superconductivity area, we will present the smallest molecular superconductor ever study to date. Here, the finding of superconductivity in just four pairs of (BETS)2-GaCl4 molecules not only provides the possibility of investigating this phenomenon locally, but also opens potential applications in nanoelectronics [3]. In molecular devices area, single molecule switches and molecular rotors operated by injecting tunneling electrons from an STM tip will be presented [4,5,6]. These experiments are innovative, and are tailored to address several critical issues covering both for fundamental understanding, and for demonstration of novel atom/molecule based nanodevices.

 

References:
[1] S.-W. Hla. STM Single Atom/Molecule Manipulation and Its Application to Nanoscience and Technology. J. Vac. Sci. Technol. B 23  1351-1360. [invited article] (2005).
[2] D. Serrate, P. Ferriani, Y. Yoshida, S.-W. Hla, M. Menzel, K. von Bergmann, S. Heinze, A. Kubetzka, and R. Wiesendanger. Imaging and Manipulating the Spin Direction of Individual Atoms, Nature Nanotechnology in press.
[3] K. Clark, A. Hassanien, S. Khan, K.-F. Braun, H. Tanaka, and S.-W. Hla. Superconductivity in Just Four Pairs of (BETS)2 GaCl4 Molecules, Nature Nanotechnology, doi:10.1038/nnano.2010.41 (2010).
[4] V. Iancu, A. Deshpande, and S.-W. Hla. Manipulation of Kondo Effect via Two Dimensional Molecular Assembly. Phys. Rev. Lett. 97  266603 (2006).
[5] V. Iancu, A. Deshpande, and S.-W. Hla. Manipulating Kondo Temperature via Single Molecule Switching. Nano Lett. 6  820-823 (2006).
[6] V. Iancu, and S.-W. Hla. Realizing of a Four-Step Molecular Switch in Scanning Tunneling Microscope Manipulation of Single Chlorophyll-a Molecules. Proc. Nat. Acad. Sci. 103  13718-13721 (2006).