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Photoelectron spectroscopy studies of PTCDI on Ag/Si(111)-root 3 x root 3
Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).ORCID-id: 0000-0003-1583-1731
Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).ORCID-id: 0000-0003-4165-1515
2018 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 149, nr 4, artikel-id 044702Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

3,4,9,10-perylene tetracarboxylic diimide molecules were evaporated onto a Ag/Si(111)-root 3 x root 3 surface and studied using photoelectron spectroscopy and near edge X-ray absorption fine structure (NEXAFS). All core levels related to the imide group of the molecules showed a partial shift to lower binding energies at low coverages. In NEXAFS spectra, the first transitions to the unoccupied states were weaker at low coverages compared to thicker films. Also, extra states in the valence band between the regular highest occupied molecular orbital and the Fermi level were found at low coverages. These changes were explained by two types of molecules. Due to charge transfer from the surface, these two types have different interactions between the imide group and the substrate. As a result, one type has a partially filled lowest unoccupied molecular orbital while the other type does not. Published by AIP Publishing.

Ort, förlag, år, upplaga, sidor
American Institute of Physics (AIP), 2018. Vol. 149, nr 4, artikel-id 044702
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Forskningsämne
Fysik
Identifikatorer
URN: urn:nbn:se:kau:diva-69377DOI: 10.1063/1.5038721ISI: 000440586200047PubMedID: 30068162OAI: oai:DiVA.org:kau-69377DiVA, id: diva2:1250183
Tillgänglig från: 2018-09-21 Skapad: 2018-09-21 Senast uppdaterad: 2019-08-15Bibliografiskt granskad
Ingår i avhandling
1. Electronic Structure and Film Morphology Studies of PTCDI on Metal/Semiconductor Surfaces
Öppna denna publikation i ny flik eller fönster >>Electronic Structure and Film Morphology Studies of PTCDI on Metal/Semiconductor Surfaces
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Organic semiconductors have received increasing attention over the last decades as potential alternatives for inorganic semiconductors. The properties of these films are highly dependent on their structural order. Of special interest is the interface between the film and its substrate, since the structure of the interface and the first few layers decide the growth of the rest of the film. The interface structure is determined by the substrate/molecule interactions, the intermolecular interactions and the growth conditions.

In this thesis, thin films of the organic semiconductor PTCDI have been studied using complementary microscopy and spectroscopy techniques on two metal-induced surface reconstructions, Ag/Si(111)-√3×√3 and Sn/Si(111)-2√3×2√3. These surfaces were chosen because they have different reactivities and surface periodicities. On the weakly interacting Ag-terminated surface, the film growth is mainly governed by the intermolecular interactions. This leads to well-ordered films that grow layer-by-layer. The interaction with the substrate is through electron charge transfer to the molecules from the substrate. This results in two different types of molecules with different electronic structure, which are identified using both STM images and PES spectra. On the more strongly interacting Sn-terminated surface the molecules adsorb in specific adsorption geometries and form 1D rows. At around 0.5 ML coverage the rows also interact with each other and form a 4√3×2√3 reconstruction and beyond one ML coverage the growth is characterized as island growth. The interaction with the substrate is mainly due to heavy electron charge transfer from the Sn atoms in the substrate to the C atoms in the imide group, but also the N atoms and the perylene core in PTCDI are involved. In these systems, the interactions with the surfaces result in new states inside the HOMO-LUMO gap, and the intermolecular interactions are dominated by O···H and O···H-N hydrogen bondings.

Abstract [en]

In our modern world we are surrounded by electronic devices that have become integral to how we live our lives. Central to most electrical devices are semiconductors such as silicon. The last decades a new type of materials, organic semiconductors, have received increasing attention. There exists a wide variety of these materials with a wide range of properties, so an organic molecule can be selected or even tailored for specific applications. Their tunable electronic properties have made it possible to use them in devices such as solar cells and light emitting diodes. Organic semiconductors have additional benefits, such as low weight and mechanical flexibility, which opens the horizon for new potential novel applications. A common device architecture involves layers of organic semiconductors sandwiched between metallic or semiconducting electrodes.

The thesis presents the use of complementary microscopy and spectroscopy methods to study thin films of the organic semiconductor PTCDI on two different semiconductor surfaces with different interaction strengths. The morphology of the film and its interface with the substrates are investigated. Additionally, the molecular interaction with these substrates are studied in detail.

Ort, förlag, år, upplaga, sidor
Karlstad: Karlstads universitet, 2018. s. 55
Serie
Karlstad University Studies, ISSN 1403-8099 ; 2018:57
Nyckelord
PTCDI, STM, LEED, XPS, UPS, NEXAFS, Organic Films, Semicondcutor Surfaces, Electronic Structure, Molecular Interactions, Film Morphology
Nationell ämneskategori
Den kondenserade materiens fysik
Forskningsämne
Fysik
Identifikatorer
urn:nbn:se:kau:diva-70262 (URN)978-91-7063-898-5 (ISBN)978-91-7063-993-7 (ISBN)
Disputation
2019-01-25, Eva Eriksson-salen, 21A 342, 651 88 Karlstad, Karlstad, 13:15 (Engelska)
Opponent
Handledare
Anmärkning

Paper 4 published in the thesis as manuscript. Now published.

Tillgänglig från: 2018-12-20 Skapad: 2018-11-22 Senast uppdaterad: 2019-02-14Bibliografiskt granskad

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Emanuelsson, ChristianJohansson, LarsZhang, Hanmin

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Journal of Chemical Physics
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