Direct experimental evidence for substrate adatom incorporation into a molecular overlayer

While the phenomenon of metal substrate adatom incorporation into molecular overlayers is generally believed to occur in several systems, the experimental evidence for this relies on the interpretation of scanning tunnelling microscopy (STM) images, which can be ambiguous and provides no quantitativ...

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Published inarXiv.org
Main Authors Mousley, Philip J, Rochford, Luke A, Ryan, Paul T P, Blowey, Phil J, Lawrence, James, Duncan, David A, Hussain, Hadeel, Billal Sohail, Tien-Lin, Lee, Bell, Gavin R, Costantini, Giovanni, Maurer, Reinhard J, Nicklin, Chris, Woodruff, D Phil
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 19.04.2022
Subjects
Adatoms
Density functional theory
Low energy electron diffraction
Mathematical analysis
Photoelectrons
Scanning tunneling microscopy
Soft x rays
Standing waves
Substrates
Surface properties
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Summary:While the phenomenon of metal substrate adatom incorporation into molecular overlayers is generally believed to occur in several systems, the experimental evidence for this relies on the interpretation of scanning tunnelling microscopy (STM) images, which can be ambiguous and provides no quantitative structural information. We show that surface X-ray diffraction (SXRD) uniquely provides unambiguous identification of these metal adatoms. We present the results of a detailed structural study of the Au(111)-F4TCNQ system, combining surface characterisation by STM, low energy electron diffraction and soft X-ray photoelectron spectroscopy with quantitative experimental structural information from normal incidence X-ray standing waves (NIXSW) and SXRD, together with dispersion corrected density functional theory (DFT) calculations. Excellent agreement is found between the NIXSW data and the DFT calculations regarding the height and conformation of the adsorbed molecule, which has a twisted geometry rather than the previously supposed inverted bowl shape. SXRD measurements provide unequivocal evidence for the presence and location of Au adatoms, while the DFT calculations show this reconstruction to be strongly energetically favoured.
ISSN:2331-8422