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Alkyl chain assisted thin film growth of 2,7-dioctyloxy-benzothienobenzothiophene
Authors:
Harald
Spreitzer
(Technische Universität Graz)
,
Benjamin
Kaufmann
(Institut für Physik, Montanuniversität Leoben)
,
Christian
Ruzié
(Université Libre de Bruxelles (ULB))
,
Christian
Rothel
(Technische Universität Graz)
,
Thomas
Arnold
(University Bath; ISIS Neutron and Muon Source; Diamond Light Source; European Spallation Source ERIC)
,
Yves H.
Geerts
(Université Libre de Bruxelles (ULB))
,
Christian
Teichert
(Institut für Physik, Montanuniversität Leoben)
,
Roland
Resel
(Technische Universität Graz)
,
Andrew O. F.
Jones
(Technische Universität Graz; Anton Paar GmbH)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Journal Of Materials Chemistry C
, VOL 26
State:
Published (Approved)
Published:
June 2019
Diamond Proposal Number(s):
13569

Abstract: An understanding of the thin film growth modes of substrate-induced polymorphs allows a deeper insight into the origin of this class of materials. Their onset of crystallisation, the subsequent crystal growth, the evolution of the thin film morphology and the transfer to the equilibrium bulk structure are still not fully understood. This work investigates the thin film formation of a conjugated molecule with terminal alkyl chains. Thin films of 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene were grown by physical vapor deposition on silicon oxide surfaces with varying the film thicknesses from the sub-monolayer regime up to 33 layer thick films. Additionally, the substrate temperature and deposition rate were varied. The films were investigated by atomic force microscopy, X-ray reflectivity and grazing incidence X-ray diffraction. The first growth stage is a closed monolayer with a thickness of 3 nm formed by upright-standing molecules. It is found that the substrate-induced crystal structure is already formed within the first monolayer and continues its growth up to the largest investigated film thickness. The characteristic morphology is terraced islands over the whole thickness range. On top of the first monolayer a morphology with several terrace levels appears, which is associated with a rapid increase of the surface roughness. At larger film thicknesses (≥13 nm) the number of terrace steps does not increase significantly, so that the surface roughness only increases slowly. This work shows that molecules with terminal alkyl chains can form a substrate-induced phase up to large film thicknesses without the appearance of the equilibrium bulk phase.
Diamond Keywords: Semiconductors
Subject Areas:
Materials,
Chemistry,
Physics
Instruments:
I07-Surface & interface diffraction
Added On:
04/07/2019 13:59
Documents:
fhfh4b4b4.pdf
Discipline Tags:
Surfaces
Physics
Physical Chemistry
Chemistry
Materials Science
interfaces and thin films
Technical Tags:
Diffraction
Grazing Incidence X-ray Diffraction (GIXD)