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O: Oberflächenphysik

O 3: Nanostrukturen I

O 3.6: Vortrag

Montag, 8. März 2004, 12:30–12:45, H36

Crystalline metallic nanostructures via e-beam lithography — •T. Block, V. Zielasek, and H. Pfnür — Institut für Festkörperphysik, Universität Hannover, Appelstrasse 2, 30167 Hannover

A combination of epitaxial metal growth with a UHV-capable lithography method offers the possibility to form 2D crystalline metallic nanostructures of arbitrary shape. Such a system can be used to study the electrical properties of metallic nanosystems, especially conductivity in low dimensions. In our experiments we use a combined SEM-STM instrument in which the 25kV electron beam and the tunneling tip can be used simultaneously at the same position of the sample. This enables us to perform electron beam lithography and subsequent investigations with STM within the same instrument. We use a lithography method based on electron beam assisted oxgen desorption from ultrathin (≈ 1 nm) SiO₂ layers on a Si(111) or Si (100)surface. Additional heating up to ≈780^oC leads to the desorption of SiO and pure crystalline Si windows. Ag deposited on top of these structures at 130K and subsequent annealing forms non-percolated clusters on the remaining SiO₂ and crystalline Ag wires on the pure Si areas with nearly step free surfaces, probably due to an electronic growth mechanism. A minimum width of 20nm, which is much smaller than the grain size of the Ag films, and a wire length of several µm have been obtained. Further optimization will decrease the linewidth. TiSi contacts, produced with conventional e-beam lithography, and the STM tip are used to connect these wires for conductivity measurements. The influence of distinct defects on electrical transport in the structures will be discussed.