Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 6: Scanning probe methods I
O 6.3: Vortrag
Montag, 26. März 2012, 11:00–11:15, MA 043
Development of a Scanning Tunneling Microscope for Measurements down to 15 mK — •Maximilian Assig, Fabian Zinser, Markus Etzkorn, Christian R. Ast, and Klaus Kern — Max-Planck-Institut für Festkörperforschung,
The investigation of novel physical phenomena implies the design and the construction of new instruments and measurement techniques, which can overcome experimental limitations and open new areas in measurement accuracy. Scanning Tunneling Microscopy (STM) is a technique for probing the electronic structure of single adsorbed atoms, molecules and nanostructures at surfaces with atomic resolution. In this contribution we present the realization of a scanning tunneling microscope (STM) operating at temperatures of 15 mK which is accomplished by attaching the STM to a dilution refrigerator. We can apply high magnetic fields up to 14 T perpendicular and 0.5 T parallel to the sample surface. An ultra high vacuum (UHV) preparation chamber is attached to the cryostat allowing in situ preparation of the samples to be investigated. The electronic resolution of our STM was verified by taking tunneling spectra between a superconducting Aluminum tip and a Cu(111) surface at the base temperature of the cryostat. From fits to the BCS theory of superconductivity we were able to extract an upper limit for the effective temperature of the electrons which is Teff = 87 ± 3 mK for our best measurement. This corresponds to an energy resolution of Δ E=3.5kbT = 26 ± 1 µeV.