Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Electronic and Optical Properties of Organic Systems II
CPP 7.3: Vortrag
Montag, 22. März 2010, 14:30–14:45, H39
Refined determination of anisotropic dielectric tensor of α-PTCDA in the visible — Maria Isabel Alonso1, Miquel Garriga1, Josep Oriol Osso2, Frank Schreiber3, Linus Gisslen4, and •Reinhard Scholz4 — 1Institut de Ciència de Materials de Barcelona, CSIC — 2MATGAS, Campus de la Universitat Autònoma Barcelona — 3Institut für Angewandte Physik, Universität Tübingen — 4Walter Schottky Institut, Technische Universität München
Spectroscopic ellipsometry measurements obtained on the (102) surface of α-PTCDA are analysed with an improved scheme for the propagation of the electromagnetic wave through the monoclinic crystal [1,2]. In this approach, the exact ellipsometric equations are solved numerically within a 4×4 transfer matrix algorithm. The resulting dielectric tensor shows a pronounced anisotropy in the plane defined by the molecular transition dipoles oriented along the long axes of the two basis molecules in the unit cell, revealing a Davydov splitting of about 0.03 eV between the lowest subbands contributing to the optical response. The experimental findings are interpreted with an exciton model accounting for Frenkel excitons and charge transfer states along the stacking direction, corroborating previous assignments of the charge transfer state below neutral molecular excitations [3].
[1] M. I. Alonso, M. Garriga, N. Karl, J. O. Ossó, and F. Schreiber, Org. Electron. 3, 23 (2002).
[2] M. I. Alonso and M. Garriga, Thin Solid Films 455-456, 124 (2004).
[3] L. Gisslén and R. Scholz, Phys. Rev. B 80, 115309 (2009).