Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 17: Scanning Probe Techniques: Method Development II
O 17.9: Vortrag
Montag, 20. März 2017, 17:45–18:00, TRE Phy
Imaging and quantification of work function variations on a nanostructured surface with scanning quantum dot microscopy — •Christian Wagner1,2, Matthew F. B. Green1,2, Philipp Leinen1,2, Michael Maiworm3, Taner Esat1,2, Rolf Findeisen3, Ruslan Temirov1,2, and F. Stefan Tautz1,2 — 1Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, Germany — 2JARA-Fundamentals of Future Information Technology — 3Institute for Automation Engineering (IFAT), Otto-von-Guericke Universität Magdeburg, Germany
The properties of a surface are crucially influenced by its electrostatic potential landscape. This landscape is formed by work function variations, e.g., due to adsorbate layers and by the local fields of edges and point-like impurities. When imaging the surface potential it is desirable to observe all these effects on equal footing. We demonstrate that scanning quantum dot microscopy (SQDM) enables precise quantification of work function variations for structures down to 10 nm in diameter and simultaneous imaging of individual atomic-scale defects. This is possible since SQDM is essentially based on a point-like probe, a molecular quantum dot, and thus avoids the averaging effects which are intrinsic to Kelvin probe force microscopy (KPFM) and which depend on tip size, shape and height. Paradoxically, in SQDM a blunter AFM tip yields sharper images due to electrostatic screening. We exemplify our method by imaging the interface dipole of islands of perylene-tetracarboxylic dianhydride (PTCDA) on Ag(111) and determining its value to be Δ φ=145±10 mV.