Regensburg 2007 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 4: Nanoengineered Thin Films
DS 4.3: Vortrag
Montag, 26. März 2007, 11:45–12:00, H34
Template-Directed Growth -- When Control is Lost — •Felix Kalischewski1, Jia Zhu2, and Andreas Heuer1 — 1Institut für Physikalische Chemie, Universität Münster, 48149 Münster — 2Physikalisches Institut, Universität Münster, 48149 Münster
Template-directed aggregation/crystallization is widely used to build architectures of functional materials. In this technique, substrate surfaces are pre-patterned to define the places of aggregation for the functional material, which is then added to the substrate e.g. by molecular beam deposition. Ideally, the deposited material will diffuse along the surface until a pattern site is met and it is immobilized. If, however, the distance between the pattern sites is too large or the deposition flux is too high, it becomes likely that a critical number of molecules aggregates and a stable 2d-nucleus is formed on an off-pattern position. At this point the intended nucleation control is lost and structural errors occur.
We focus on the behavior of this transition point. Intuitively, one would expect the transition when the area-density of the pattern is equal to the saturated density of the 2d-nuclei on an un-patterned substrate. This is not exact however, because the maximum concentration of adsorbed molecules, which is responsible for the formation of new nuclei, strongly depends on the specific pattern. We model the resulting concentration field by a set of differential equations which are solved numerically as well as analytically. In addition, we apply off-lattice Monte-Carlo simulations and compare the results to experimental data.