Dr. Chr. Bobisch, Department of Physics, University of Duisburg-Essen, Germany: Transport phenomena on the atomic scale
|27 January 2011||FWN-Building 5111.0080, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Dr. Christian Bobisch|
Department of Physics, University. of Duisburg-Essen, Germany
|Title:||Transport phenomena on the atomic scale|
The scanning tunneling microscope (STM) is an ideal tool to study surface phenomena on the atomic scale. Beside the analysis of topographic features and the geometric structure of surfaces, it offers the possibility to study their electronic structure. Moreover it can be used to characterize nm-sized objects like single organic molecules adsorbed on surfaces.
Firstly, I will present a STM based analysis of two different 2-dimensional electron gas (2DEG) systems. On the one hand the electronic surface structure of epitaxial thin films of bismuth on top of a Si(111)-7x7 substrate was analyzed [1,2]. Using scanning tunneling spectroscopy (STS) and imaging the local density of states (dI/dV imaging) the scattering of electrons propagating in the complex surface state structure of Bi(111) was analyzed in detail.
For the Si(111)-√3 x√3-Ag surface the local variation of the electrochemical potential was studied, if a current is applied across the 2DEG of this surface. A multiprobe STM is used to apply the current across the surface while the topography as well as the electrochemical potential can be measured simultaneously. The data reveal a stepwise decay of the electrochemical potential at surface steps, grain boundaries etc., thus the stepwise decay can be addressed to local resistivities on the atomic level .
The last part deals with the organic dye copper-phthalocyanine (CuPc) adsorbed onto a Cu(111) substrate. Low temperature scanning tunneling microscopy allows analyzing a current induced motion of single CuPc molecules. Especially a switching process between transient states of the adsorbed CuPc molecule can be imaged and analyzed with sub molecular precision.
 T. Nagao, T. Doi, T. Sekiguchi, and S. Hasegawa, Phys. Jpn. J. Appl. Phys. 39, 4567 (2000).
 C. A. Bobisch, A. Bannani, Yu. M. Koroteev, G. Bihlmayer, E.V. Chulkov, and R. Möller, Phys. Rev. Lett. 102, 136807 (2009).
 J. Homoth, M. Wenderoth, T. Druga, L. Winking, R.G. Ulbrich, C.A. Bobisch, B. Weyers, A. Bannani, E. Zubkov, A.M. Bernhart, M.R. Kaspers, R. Möller, Nano Letters 9, 1588 (2009).
|Last modified:||12 September 2014 11.21 a.m.|