Regensburg 2007 – scientific programme
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DS: Fachverband Dünne Schichten
DS 1: Organic Thin Films I
DS 1.5: Talk
Monday, March 26, 2007, 10:30–10:45, H32
Combined Spectroscopic Ellipsometry and Reflectance Anisotropy Spectroscopy Measurement of Phthalocyanines on ZnO (0001) Semiconducting Surface — •Sindu John Louis, Marion Friedrich, and Dietrich Zahn — Chemnitz University of Technology, Semiconductor Physics, D-09107 Chemnitz, Germany
Phthalocyanines (Pcs) are important class of materials exhibiting high thermal and chemical stability and also high optical absorption in the visible range. The growth of this molecule on the wide gap (3.2 eV) semiconductor ZnO of wurtzite structure is an interesting study. Detailed information about the interaction between the Pcs and the ZnO substrate can be obtained from Spectroscopic Ellipsometric (SE) measurements and the extent of in-plane anisotropy can be detected by the Reflectance Anisotropy Spectroscopy (RAS) measurements.
Thin films of Pcs are prepared by organic molecular beam deposition method in ultrahigh vacuum conditions. Spectroscopic ellipsometric studies were carried out using Variable Angle Spectroscopic Ellipsometer (VASE) in the NIR-Vis-UV range from 0.75 eV to 5 eV. RAS is sensitive to very small anisotropies of order 10−3 or even smaller. The accessible range is from 1.5 eV to 5.5 eV. Both these RAS and SE measurements are performed in situ together.
Since the optical absorption of the Pcs in the Q band region (around 2 eV) is due to π to π* transitions of the macro cycle π - system, any change in the line shape of imaginary part of the dielectric function for ultra thin layers provide insight to the interaction with the surface through π - orbitals.