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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.67: Poster

Tuesday, February 26, 2008, 14:30–20:00, Poster A

Pentacene thin films on diamond surfaces: effect of surface termination — •W. Gajewski¹, F. Buth¹, M. Huth², B. Nickel², M. Stutzmann¹, and J.A. Garrido¹ — ¹Walter Schottky Institute, TU-Munich, Garching — ²Physics Department, Ludwig-Maximilians University, Munich

We investigate the effect of diamond surface termination by oxygen or hydrogen on the structural and optoelectronic properties of pentacene thin films deposited on diamond. Pentacene films with thicknesses from 3 to 50 nm were deposited on O- and H-terminated diamond films, as well as on SiO2 surfaces for comparison. On O-terminated diamond surfaces, pentacene molecules are oriented almost perpendicular to the substrate, as revealed by X-ray diffraction and AFM. For H-terminated diamond surfaces the morphology of the pentacene films is much more complex, probably due to a Stransky-Krastanov like growth mode characterized by a first flat molecular layer followed by 3D island growth. Optical absorption as well as spectrally resolved photocurrent measurements in the energy range 0.5-6.0 eV performed at temperatures from 80 to 350K allow the detection of the excitonics and the HOMO-LUMO transition in the pentacene film, as well as specific charge transfer processes between diamond and pentacene. Current-voltage characteristics recorded for pentacene films with various thickness in the dark and under illumination reveal a complex temperature and electric field dependence of the electronic transport at the diamond/pentacene interface.