Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 48: Scanning Probe Methods I

O 48.10: Vortrag

Mittwoch, 2. April 2014, 12:45–13:00, GER 38

Looking for the Origin of Power Laws in Electric Field Assisted Tunneling — •H. Cabrera, D.A. Zanin, L.G. De Pietro, A. Vindigni, U. Ramsperger, and D. Pescia — Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland

We have measured the voltage vs distance characteristics at constant current I of a tunnel diodelike junction consisting of an electron emitting sharp tip placed at a variable distance d from a planar anode. Such a junction is used e.g. in Scanning Tunneling Microscopy (STM) and in the topografiner technology. By mounting the tip onto a piezocrystal, which can move the tip perpendicularly to the surface, the distance d can be varied, its value can be also double checked by an optical sensor device. At sufficiently large distances, i.e. in the regime of electric field assisted quantum tunneling, the V−d characteristic curves for different currents follow approximately a power law, the exponent λ being independent of the current. Here we compare and discuss the origin of the observed power law and the measured value of it in terms of electrostatic properties of the tip-plane junction, taking the geometry of the tip as a hyperboloid of revolution.