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Thursday, 04 August 2016

Mechanism for self-arrangement of a 2D misfit dislocation array in complex oxide epitaxial ultrathin films

Researchers from ICN2, together with colleagues from ICMAB, MIT and the University of Belgrade, have followed the formation and self-organisation of misfit dislocations in mismatched epitaxial films. They were able to form a perfect array of parallel lines with nanometre separation. Dr José Santiso, Division Leader of the ICN2 Nanomaterials Growth Division, is the first author of the article, together with Dr Jaume Roqueta.

Strain engineering in thin epitaxial films of transition metal oxides with perovskite structure has become an important field of study in the past decade. In a work led by researchers from the ICN2, and recently published in ACS Applied Materians & Interfaces, authors have been able to follow the formation and self-organisation of misfit dislocations in mismatched epitaxial films with different thickness up to the point they form a perfect array of parallel lines with nanometre separation. 

These nanostructured films can be considered as a nanocomposite consisting of a fraction of the film volume that is either fully strained or fully relaxed, along with evenly spaced nanometre regions around the dislocation lines, which show physical properties different from the rest of the material. This can be a very general phenomenon in a wide variety of mismatched heterostructures. The control over the thickness range where this type of nanocomposite material is formed and dominates the physical properties of the films could be considered as a separate phase in the material phase diagram.

Dr José Santiso, Division Leader of the ICN2 Nanomaterials Growth Division, is the first author of the article, together with Dr Jaume Roqueta. The last author of the paper is Dr Felip Sandiumenge, from the Materials Science Institute of Barcelona (ICMAB-CSIC). The work also includes authors from the Massachusetts Institute of Technology (MIT) (Cambridge, United States) and the University of Belgrade (Belgrade, Serbia). It combined different techniques, including 2D X-ray reciprocal space mapping experiments performed on beamline BM25 at the European Synchrotron Radiation Facility (ESRF) (Grenoble, France). 

Article reference:
José Santiso, Jaume Roqueta, Núria Bagués, Carlos Frontera, Zorica Konstantinovic, Qiyang Lu, Bilge Yildiz, Benjamín Martínez, Alberto Pomar, Lluis Balcells, and Felip Sandiumenge. Self-Arranged Misfit Dislocation Network Formation upon Strain Release in La0.7Sr0.3MnO3/LaAlO3(100) Epitaxial Films under Compressive Strain. ACS Appl. Mater. Interfaces, 2016; 8 (26): 16823–16832.
http://pubsdc3.acs.org/doi/full/10.1021/acsami.6b02896