Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 32: Focus Session: Charge Transport at Surfaces and Nanostructures with Multi-probe Techniques I

O 32.5: Invited Talk

Tuesday, March 21, 2017, 11:45–12:15, WIL C307

Probing electron transport with atomic scale precision — •Christian A. Bobisch — Faculty of Physics, Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany

To track down the elementary contributions to macroscopic properties such as the electric resistance, nanoscale electron transport measurements are essential. I will discuss that this can be achieved by combining scanning tunneling microscopy (STM) with transport measurements. We use a four probe STM to perform scanning tunneling potentiometry (STP)[1] which gives direct access to the topography and the lateral variations of the electrochemical surface potential µ_ec under realistic conditions, i.e. while a lateral current flows along the surface. Thereby, we analyze the spatial variations of µ_ec with nm lateral resolution. In particular, we study the interaction of conduction electrons with defect sites, e.g., atomic step edges or grain boundaries.

The two dimensional electron gas system of Si(111)-√3×√3:Ag is a model 2D system, where scattering at step edges and grain boundaries is identified as major contribution to the resistance [2]. Also at the surface of the topological insulator Bi₂Se₃ [3] we find step-like variations of µ_ec in the vicinity of defects which is a fingerprint of electron scattering [4]. Here, we evaluate the electric resistivities of individual step edges and grain boundaries.

[1] Appl. Phys. Lett. 48, 514 (1986). [2] Nano Letters 9, 1588 (2009). [3] Rev. Mod. Phys. 82, 3045 (2010). [4] Nature Comm. 7, 11381 (2016).