Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 76: Nanostructures at surfaces: Wires, tubes

O 76.3: Vortrag

Donnerstag, 25. März 2010, 15:30–15:45, H38

Potentiometry measurements of Pb wires on vicinal Si(557) produced by electron-beam stimulated thermal desorption of oxygen — •Jan Rönspies and Herbert Pfnür — Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover, Germany

We explored the structural limits of unconventional electron beam lithography by directly writing with an electron beam into ultra-thin SiO₂ films. These bare silicon window structures are suitable for growing contiguous metallic nanowires with a thickness of a few monolayers. The Auger excitation process necessary for electron-beam stimulated thermal desorption of oxygen (EBSTD) allows generation of single wire structures between two macroscopic metallic contact pads. The prepared line was filled with Pb and by subsequent processing steps a wetting layer remains inside the wire structure. Applying this combination of processes to a regularly stepped Si(557) sample which consists of a periodic array of small (111) and (112) oriented mini-facets with an average periodicity of 5.7nm normal to the steps, line widths close to the resolution of the electron microscope of 5nm were obtained. Using a STM tip and the macroscopic pads in a potentiometric geometry we were able to identify the quantized nature of ultrasmall structures and their conductance behavior over a range of a few micrometers. These uncovered structures with lateral dimensions down to 10nm were analyzed further by potentiometry using scanning tunneling microscopy. We found a significant potential drop in the order of 200µ V /nm at step sites which are probably related to contact resistance.