Dresden 2011 – scientific programme
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DS: Fachverband Dünne Schichten
DS 65: Organic Thin Films IV
DS 65.1: Talk
Friday, March 18, 2011, 16:00–16:15, GER 38
Changes in optical absorption during film growth — •Harald Graaf1, Christopher Keil2, and Derck Schlettwein2 — 1Center for nanostructured Materials (nanoMA), Institut für Physik, Technische Universität Chemnitz, 09107 Chemnitz — 2Institut für Angewandte Physik, Justus-Liebig-Universität Gießen, 35392 Gießen
The optical properties of organic thin films are mainly dominated by the (ordered) arrangement of the molecules in the solid. Beside this also the interface to the substrate influences the optical characteristics. This can be seen in absorption measurements taken during the growth of such thin films. Here a clear blue shift of the lowest energy transition with decreasing film thickness can be obtained.
In the literature different explanations are given: decrease in dimension of coupled aggregates [1], quantum confinement of the layer [2], missing nearest neighbour approximation [3] and microscopic polarizability [4]. We will show recent results on different organic materials with comparable optical properties in solution but divers properties in the bulk. Also changes in the substrate will be presented and discussed with regard to the suggested models.
[1] Chau et al. J.Phys.Chem. 97 (1993) 2699
[2] Shen et al. Phys.Rev.B 55 (1997) 10578
[3] Heinemeyer et al. Phys.Rev.Lett. 104 (2010) 257401
[4] Beckers et al. J.Phys.:Condens.Matter 10 (1998) 1721