CoPc on Ag(100): getting the most out of PEEM images
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DPG Frühjahrstagung SKM 2023
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We use photoelectron emission microscopy (PEEM) and the Anderson method to study in situ the thin-film growth of cobalt-phthalocyanine (CoPc) on Ag(100) surfaces. Based on the Fowler-DuBridge theory, we were able to correlate the evolution of the mean electron yield acquired with PEEM for coverages up to two molecular layers of CoPc to the global work function changes measured with the Anderson method. For coverages above two monolayers, the transients measured with the Anderson method and those obtained with PEEM show different trends allowing us to determine the inelastic mean free path of the low-energy electrons while passing through the third layer of CoPc. Already before (and during) the condensation of solid phases (2D islands or 3D crystallites), there is a dilute 2D gas phase consisting of individual molecules diffusing across the surface or clusters, which can not be resolved with PEEM. Therefore, we discuss, how image features below and above the resolution limit of a PEEM affect the mean electron yield and the (normalized) standard deviation.
 Th. Wagner et al., ACS Appl. Mater. Interfaces 12 (2022), 23983?23989  Th. Wagner et al., Ultramicrocopy 233 (2022), 113427