Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 38: Organic Molecules on Inorganic Substrates II: Electronic Properties and Charge Transfer

O 38.2: Vortrag

Dienstag, 2. April 2019, 14:15–14:30, H24

Molecular Orbital Imaging Beyond the First Monolayer — •Christian Metzger¹, Manuel Grimm¹, Martin Graus¹, Kiana Baumgärtner¹, Matteo Jugovac², Giovanni Zamborlini², Vitaliy Feyer², Achim Schöll¹, and Friedrich Reinert¹ — ¹Julius-Maximilians-Universität Würzburg, Experimental Physics VII, 97074 Würzburg, Germany — ²Forschungszentrum Jülich GmbH, Paul Grünberg Institute (PGI-6), 52425 Jülich, Germany

We present a method to determine the geometric alignment of molecular compounds within evaporated thin films by a combination of experimental orbital imaging combined with photoemission matrix element calculations on the example of pentacene bilayers on Ag(110). The technique utilizes angle-resolved photoemission spectroscopy (ARPES) measurements at a photoemission electron microscope in Fourier-space imaging mode (kPEEM), which enables the efficient detection of photoelectrons emitted into the entire hemisphere above the sample. By simulating different tilt angles of isolated pentacene molecules and comparing the resulting photoemission intensity distribution with momentum maps measured on molecular multilayers, one is able to determine the molecules' tilt angles for each separate layer independently from one another. We determine that the flat-lying molecules of the first monolayer on the metal substrate exhibit a noticable tilt angle upon adsorption of a second molecular layer. The molecules in the second layer above the substrate feature a larger inclination, which is evidence of the gradual relaxation into the pentacene bulk structure with increasing film thickness.