Void-mediated coherency-strain relaxation and impediment of cubic-to-hexagonal transformation in epitaxial metastable metal/semiconductor TiN/Al0.72Sc0.28N multilayers

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dc.contributor.authorGarbrecht, Magnusen
dc.contributor.authorHultman, Larsen
dc.contributor.authorFawey, Mohammed H.en
dc.contributor.authorSands, Timothy D.en
dc.contributor.authorSaha, Bivasen
dc.contributor.departmentElectrical and Computer Engineeringen
dc.contributor.departmentMaterials Science and Engineering (MSE)en
dc.date.accessioned2019-10-03T12:37:21Zen
dc.date.available2019-10-03T12:37:21Zen
dc.date.issued2017-08-17en
dc.description.abstractBulk metastable phases can be stabilized during thin-film growth by employing substrates with similar crystal structure and lattice parameter, albeit over a thickness range limited by coherency-strain relaxation. Expanding that strategy, growth of superlattices comprising one stable and another metastable compound with similar crystal structure and lattice parameters are known to yield epitaxial stabilization over a few nanometers of thickness. In this work, the high-pressure rocksalt (B1) phase of Al0.72Sc0.28N was stabilized epitaxially in a multilayer with TiN with thicknesses of up to 26 nm. In order to investigate the microstructural changes leading to the phase transformation of the metastable B1 phase to its wurtzite allomorph, we demonstrate a design based on a multilayer architecture with systematically varying thicknesses of the metastable compound within a constant-thickness lattice of stable metallic TiN with the cubic rocksalt structure. The multilayer films show an increasing hardness and elastic modulus for decreasing period thickness, in correspondence with both coherency-strain and Koehler hardening. The phase transition is accompanied by an increase of lattice strain with increasing multilayer periods, and resulting ultimately in coherency-strain relaxation upon phase transformation. Further, we show that the phase transformation is mediated by voids decorating the {130} planes that separate regions of different growth rates and act as additional growth fronts for wurtzite growth during the phase transformation. The TiN/(Al, Sc) N interfaces themselves remain atomically sharp and smooth until the interface structure roughens along with the epitaxial rocksalt to wurtzite transition of (Al, Sc) N. These results show the strong influence of the voids on controlling the target thickness of epitaxially stabilized thin-film growth to the range relevant for applications, such as coatings, plasmonic materials, and electronic device technology, where the mechanical integrity of the material is critical.en
dc.description.notesThe Knut and Alice Wallenberg (KAW) Foundation is acknowledged for the Electron Microscope Laboratory in Linkoping. M.G. and L.H. acknowledge financial support from the Swedish Research Council [RAC Frame Program (2011-6505), Project Grant No. 2013-4018, and a Linnaeus Grant (LiLi-NFM)] as well as the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU 2009-00971). B.S. and T.D.S. acknowledge financial support from the National Science Foundation and US Department of Energy (Award No. CBET-1048616). M.G. and B.S. acknowledge support from the Swedish Foundation for International Cooperation in Research and Higher Education (STINT). M.G. acknowledges support in specialized TEM sample preparation at the Karlsruhe Nano Micro Facility (Project ID 2015-015-010151) via V.S.K. Chakravadhanula.en
dc.description.sponsorshipSwedish Research Council [2011-6505, 2013-4018]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; National Science Foundation; US Department of Energy [CBET-1048616]; Swedish Foundation for International Cooperation in Research and Higher Education (STINT); Karlsruhe Nano Micro Facility [2015-015-010151]en
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1103/PhysRevMaterials.1.033402en
dc.identifier.issn2475-9953en
dc.identifier.issue3en
dc.identifier.other33402en
dc.identifier.urihttp://hdl.handle.net/10919/94335en
dc.identifier.volume1en
dc.language.isoenen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.titleVoid-mediated coherency-strain relaxation and impediment of cubic-to-hexagonal transformation in epitaxial metastable metal/semiconductor TiN/Al0.72Sc0.28N multilayersen
dc.title.serialPhysical Review Materialsen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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