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DS: Fachverband Dünne Schichten

DS 55: Organic Thin Films III

DS 55.5: Vortrag

Freitag, 11. März 2016, 10:30–10:45, H8

The role of Induced Density of Interface States in the Interfacial Energy Level Alignment of PTCDA — •Mahdi Samadi Khoshkhoo¹, Heiko Peisert¹, Thomas Chassé^1,2, and Marcus Scheele^1,2 — ¹Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany — ²Center for Light-Matter Interaction, Sensors & Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, 72076 Tübingen, Germany

We use various type of diverse substrates with different work functions and different coupling interactions to investigate the electronic structure of PTCDA using ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS) as well as complementary electrostatic potential calculations. For thick enough layers of PTCDA, nearly unchanged injection barriers on all substrates are observed without any dependence on the type of substrate (unreactive, reactive or passivated metals and polymers). The Fermi level is observed to be strongly pinned at the charge neutrality level (CNL) of the organic semiconductor. For lower thicknesses of PTCDA, this universal Fermi level pinning is perturbed and differences in the work function of up to 0.8 eV are detected, depending on the nature of the substrate and the thickness. We find near-quantitative agreement between our experimental data and electrostatic potential calculations in the framework of an expanded model of induced density of interface states (IDIS). These results provide valuable information for the design and fabrication of PTCDA-based heterostructures.