A. Bernhart

Electronic Transport on the Nanoscale: Ballistic Transmission and Ohm's Law

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 Ohms 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)-( [see text]3 x [see text]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.

Probing the electronic transport on the reconstructed Au/Ge(001) surface

Summary By using scanning tunnelling potentiometry we characterized the lateral variation of the electrochemical potential µec on the gold-induced Ge(001)-c(8 × 2)-Au surface reconstruction while a lateral current flows through the sample. On the reconstruction and across domain boundaries we find that µec shows a constant gradient as a function of the position between the contacts. In addition, nanoscale Au clusters on the surface do not show an electronic coupling to the gold-induced surface reconstruction. In combination with high resolution scanning electron microscopy and transmission electron microscopy, we conclude that an additional transport channel buried about 2 nm underneath the surface represents a major transport channel for electrons.

Current induced surface diffusion on a single-crystalline silver nanowire.

Scanning tunnelling microscopy was used to study the morphological changes of the surface of a single-crystalline silver nanowire caused by a lateral electron current. At current densities of about 1.5 × 10(7) A cm(-2), surface atoms are extracted from step edges, resulting in the motion of surface steps, islands and holes with a thickness or depth of one monolayer. Upon current reversal the direction of the material transport can be altered. The findings are interpreted in terms of the wind force.

Ballistic electron and hole transport through individual molecules

Recently the ballistic transport through organic molecules could be analyzed with submolecular resolution by an extension of ballistic electron emission microscopy. In this work we compare the results of ballistic transport of electrons and holes through C60 molecules deposited onto a Bismuth/Silicon Schottky diode. The study of hole transmission also exhibits molecular a resolved pattern in the transmission images showing the molecular periodicity of the C60 layer.

Electronic Transport on the Nanoscale

A scanning tunneling microscope with several tips is ideally suited to analyze the electronic transport through objects on the nanoscale. Two different configurations will be discussed. The lateral transport of electrons may be studied by using two tips to drive a current parallel to the surface. A third tip enables to map the corresponding electrochemical potential μ ec. Measurements for a 2D conducting layer will be discussed. To analyze the transport perpendicular to the surface, a thin metallic layer is placed on a semiconducting surface. At the interface a Schottky barrier is formed, which can only be overcome by electrons of sufficient energy. This may be used to split the tunneling current coming from the tip of the microscope, into the ballistic electrons and the electrons which underwent inelastic scattering processes. This technique has been applied to study the ballistic transport of electrons through a thin epitaxial Bi(111) layer as well as through individual molecules.

Erratum: Epitaxial Growth of Bi(111) on Si(001) [e-J. Surf. Sci. Nanotech. Vol. 7, pp. 441-447 (2009)]

In this article [1], one of the coauthors, B. Krenzer, is missing in the author list by mistake. The correct author list is the same as the one shown in this erratum.