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O: Fachverband Oberflächenphysik

O 32: Poster Session - Organic Molecules on Inorganic Substrates: Adsorption and Growth

O 32.4: Poster

Montag, 16. März 2020, 18:15–20:00, P1C

Structure of tetracene films on hydrogen-passivated Si(111) and amorphous Si — •Hazem Aldahhak¹, Jens Niederhausen², Rowan W. MacQueen², Wolf Gero Schmidt¹, Klaus Lips², and Uwe Gerstmann¹ — ¹Lehrstuhl für Theoretische Materialphysik, Universität Paderborn, 33095 Paderborn, Germany — ²Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialen und Energie GmbH, Berlin, Germany

The properties of the Tetracene (Tc)-Silicon (Si) interfaces are of particular interest when trying to augment the Si solar cells by singlet fission in Tc. Here, we combine Near-edge X-ray absorption fine structure (NEXAFS), x-ray photoelectron spectroscopy (XPS) as well as density functional theory (DFT) calculations to elucidate the structure of the first Tc monolayer on hydrogen-passivated Si(111) and amorphous Si (H:a-Si). Typically, the first monolayer is hampered by the significant dewetting tendency of Tc at room temperature. Here, we present a selective study using cooling to limit the thermal energy of the Tc molecules during growth and measurements. We find that the first Tc monolayer on cooled substrates exhibits a mixture of the bulk-like Tc (Tc I) and the surface-induced thin film (Tc II) phases. The DFT calculated total-energies and angle-dependent NEXAFS fingerprints support the measurements. Further heating of the cool Tc/H:Si(111) film to room temperature indicates structural changes towards lower Tc inclination, rendering the appearance of this phase to rely on sufficient amount of thermal energy being available.