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TT: Tiefe Temperaturen

TT 9: Transport: Nanoelectronics III - Molecular Electronics

TT 9.3: Talk

Monday, March 27, 2006, 14:30–14:45, HSZ 304

Controlled Nanogap Manufacturing for Single Molecule Contacts by Electromigration — •Veit Wagner, Arne Hoppe, and Jörg Seekamp — International University Bremen

Electrical measurements of single molecules require a pair of electrodes separated by a nanogap of only a few nanometers. Many preparation methods lack the possibility to form an additional gate electrode. We report on nanogap formation by electromigration using the substrate as additional gate electrode. A small metal wire of typically 100 nm width is broken by imposing a high current density at l-He temperature. At room temperature (RT) this approach usually leads to gaps much larger than molecular sizes. Recently Strachan et al. reported on successful nanogap production at RT by using an active control scheme for the applied voltage in dependence of the measured conductivity of the wire. Following this approach we present an alternative control scheme, which includes in addition the time derivative of the conductivity and the average noise level. Gold nanowires of 100 nm width and 20nm height with a Ti adhesion layer on a SiO2-surface were prepared by e-beam lithography. A current level of about 5 mA is usually sufficient to start the electromigration process at room temperature. We test different wire shapes, e.g. a long thin wire of constant thickness or a thick wire with a lithographically defined short narrowing. We find the long thin wire to be more demanding for our control loop than a wire with a short narrowing. The regulation behavior of our control loop for various regions of the process is discussed. With our approach we can reproducibly manufacture gaps at RT with gap sizes smaller than 10 nm.