Mapping Local Tranport Fields: Scanning Tunneling Potentiometry

Electronic Transport on the Nanoscale: Ballistic Transmission and Ohm’s Law [Nano Letters 9, 1588, (2009 )]

If a current of electrons flows through a normal conductor (in contrast to a superconductor), it is impeded by local scattering at defects as well as phonon scattering. Both effects contribute to the voltage drop observed for a macroscopic complex system as described by Ohm’s law. Although this concept is well established, it has not yet been measured around individual defects on the atomic scale. We have measured the voltage drop at a monatomic step in real space by restricting the current to a surface layer. For the Si(111)-(
3 ×
3)-Ag surface a monotonous transition with a width below 1 nm was found. A numerical analysis of the data maps the current flow through the complex network and the interplay between defect-free terraces and monatomic steps.

Financial support from the Deutsche Forschungsgemeinschaft through SFB 602 Complex structures in condensed matter from atomic to mesoscopic scales via TP A7 is gratefully acknowledged.

In collaboration with:

C. A. Bobisch, B. Weyers, A. Bannani, E. Zubkov, A. M. Bernhart,M. R. Kaspers, and R. Möller, Department of Physics and Center of Nano Integration Duisburg-Essen (CeNIDE), UniVersity of Duisburg-Essen, Germany