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Core levels, valence band structures and unoccupied states of biphenylene films
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Biphenylene is a cyclic hydrocarbon made of two benzene rings connected by a cyclobutadiene ring. We performed a photoemission and near-edge absorption (PES and NEXAFS) spectroscopy investigation on biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. By PES we studied the occupied core and valence levels, while NEXAFS gave us information on the unoccupied states. The obtained results have been compared to previous gas phase spectra and density functional theory (DFT) calculations on single biphenylene molecule to get insights in the film electronic structure and possible modification induces by the adsorption. Furthermore, NEXAFS results of biphenylene films of different thicknesses allowed the characterization of the molecular arrangement in the overlayer on the Cu surface and helped to clarify the substrate-molecule interactions.

National Category
Atom and Molecular Physics and Optics
URN: urn:nbn:se:uu:diva-281566OAI: oai:DiVA.org:uu-281566DiVA: diva2:914612
Available from: 2016-03-24 Created: 2016-03-24 Last updated: 2016-04-29
In thesis
1. Complex Excitations in Advanced Functional Materials
Open this publication in new window or tab >>Complex Excitations in Advanced Functional Materials
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Understanding the fundamental electronic properties of materials is a key step to develop innovations in many fields of technology. For example, this has allowed to design molecular based devices like organic field effect transistors, organic solar cells and molecular switches.

In this thesis, the properties of advanced functional materials, in particular metal-organic molecules and molecular building blocks of 2D materials, are investigated by means of Density Functional Theory (DFT), the GW approximation (GWA) and the Bethe-Salpeter equation (BSE), also in conjunction with experimental studies. The main focus is on calculations aiming to understand spectroscopic results.

In detail, the molecular architectures of lutetium-bis-phthalocyanine (LuPc2) on clean and hydrogenated vicinal Si(100)2×1, and of the biphenylene molecule on Cu(111) were analysed by means of X-ray Photoelectron spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy; DFT calculations were performed to obtain insights into the atomic and electronic structures. Furthermore, detailed information about the electronic states of the gas phase iron phthalocyanine (FePc) and of the gas phase biphenylene molecule were obtained through XPS and NEXAFS spectroscopy. I have studied by means of DFT, multiplet and GWA calculations the electronic correlation effects in these systems. Also the optical, electronic and excitonic properties of a hypothetical 2D material based on the biphenylene molecule were investigated by GWA and BSE calculations. Monolayers of metal-free phthalocyanine (H2Pc) on Au(111) and of FePc on Au(111) and Cu(100)c(2×2)-2N/Cu(111) with and without pyridine modifier were studied by XPS and final state calculations. A multiplet approach to compute L-edges employing the hybridizations function, known from dynamical mean field theory, was proposed and applied to transition metal oxides.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 90 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1365
X-ray Absorption Spectroscopy, Photoelectron Spectroscopy, Adsorption, Phthalocyanines, Biphenylene, Excitons, Functional Materials
National Category
Condensed Matter Physics
urn:nbn:se:uu:diva-282151 (URN)978-91-554-9543-5 (ISBN)
Public defence
2016-05-13, Å80101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Available from: 2016-04-22 Created: 2016-04-03 Last updated: 2016-04-29

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