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Combined specular and off-specular reflectometry: elucidating the complex structure of soft buried interfaces

Lookup NU author(s): Professor Mark GeogheganORCiD



This is the authors' accepted manuscript of an article that has been published in its final definitive form by Wiley-Blackwell Publishing Ltd, 2021.

For re-use rights please refer to the publisher's terms and conditions.


Neutron specular reflectometry (SR) and off-specular scattering (OSS) are non­destructive techniques which, through deuteration, give a high contrast even among chemically identical species and are therefore highly suitable for investigations of soft-matter thin films. Through a combination of these two techniques, the former yielding a density profile in the direction normal to the sample surface and the latter yielding a depth-resolved in-plane lateral structure, one can obtain quite detailed information on buried morphology on length scales ranging from the order of ångströms to ∼10 µm. This is illustrated via quantitative evaluation of data on SR and OSS collected in time-of-flight (ToF) measurements of a set of films composed of immiscible polymer layers, protonated poly(methyl methacrylate) and deuterated polystyrene, undergoing a decomposition process upon annealing. Joint SR and OSS data analysis was performed by the use of a quick and robust originally developed algorithm including a common absolute-scale normalization of both types of scattering, which are intricately linked, constraining the model to a high degree. This, particularly, makes it possible to distinguish readily between different dewetting scenarios driven either by the nucleation and growth of defects (holes, protrusions etc.) or by thermal fluctuations in the buried interface between layers. Finally, the 2D OSS maps of particular cases are presented in different spaces and qualitative differences are explained, allowing also the qualitative differentiation of the in-plane structure of long-range order, the correlated roughness and bulk defects by a simple inspection of the scattering maps prior to quantitative fits

Publication metadata

Author(s): Hafner A, Gutfreund P, Toperverg BP, Jones AOF, de Silva JP, Wildes A, Fischer HE, Geoghegan M, Sferrazza M

Publication type: Article

Publication status: Published

Journal: Journal of Applied Crystallography

Year: 2021

Volume: 54

Issue: 3

Pages: 924-948

Print publication date: 01/06/2021

Online publication date: 31/05/2021

Acceptance date: 02/04/2021

Date deposited: 05/08/2021

ISSN (print): 0021-8898

ISSN (electronic): 1600-5767

Publisher: Wiley-Blackwell Publishing Ltd


DOI: 10.1107/S1600576721003575


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