Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 88: Metallic Nanostructures II (on Semiconductors)
O 88.11: Talk
Friday, February 29, 2008, 12:00–12:15, MA 005
Fabrication of metallic cones for optical near-field investigations — •Monika Fleischer1, Florian Stade1, Kai Braun2, Johannes Stadler2, Andreas Heeren1, Michael Häffner1, Marcus Sackrow2, Catrinel Stanciu2, Alfred J. Meixner2, and Dieter P. Kern1 — 1Institute of Applied Physics, Auf der Morgenstelle 10, 72076 Tübingen, Germany — 2Institute of Physical and Theoretical Chemistry, Auf der Morgenstelle 8, 72076 Tübingen, Germany
Metallic cones with dimensions of the order of 100 nm are highly favourable objects for optical near-field investigations using visible light. Upon illumination, strong electric field enhancement can be observed up to a few nanometers above the cone tip. However, fabricating well-defined metallic cones with a sharp tip on the nanoscale is nontrivial. We present a process flow in which arrays of cones are shaped from a continuous metal sandwich layer on silicon by subtractive ion milling. In the process, patterned hydrogen silsesquioxane resist (HSQ) is used as an etch mask. The resulting cones have tunable base diameters around 150 nm and tip radii down to less than 10 nm. Their optical characteristics are investigated by means of apertureless optical near-field microscopy. Field enhancement at the cone tip has been demonstrated both by simulation and by experiment. In combination, the metallic scanning probe of the microscope and the cone form a vertical antenna configuration. This antenna features a small tunable gap and strong variable field enhancement within the gap region.