Excess of boron in TiB2 superhard thin films: A combined experimental and ab initio study

Kalfagiannis, N; Volonakis, G; Tsetseris, L; Logothetidis, S

dc.contributor.author	Kalfagiannis, N	en
dc.contributor.author	Volonakis, G	en
dc.contributor.author	Tsetseris, L	en
dc.contributor.author	Logothetidis, S	en
dc.date.accessioned	2014-03-01T01:35:39Z
dc.date.available	2014-03-01T01:35:39Z
dc.date.issued	2011	en
dc.identifier.issn	0022-3727	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/21151
dc.subject.classification	Physics, Applied	en
dc.subject.other	Ab initio study	en
dc.subject.other	Atomic scale	en
dc.subject.other	B atoms	en
dc.subject.other	B incorporation	en
dc.subject.other	Controlled growth	en
dc.subject.other	First-principles calculation	en
dc.subject.other	Grain surface	en
dc.subject.other	Hexagonal structures	en
dc.subject.other	High hardness	en
dc.subject.other	Interstitials	en
dc.subject.other	Nano grains	en
dc.subject.other	Nanocrystallines	en
dc.subject.other	Over-stoichiometric	en
dc.subject.other	Structural feature	en
dc.subject.other	Substrate voltage	en
dc.subject.other	Superhard	en
dc.subject.other	Superhardness	en
dc.subject.other	Technological applications	en
dc.subject.other	Theoretical approach	en
dc.subject.other	Boron	en
dc.subject.other	Boron compounds	en
dc.subject.other	Lattice constants	en
dc.subject.other	Stoichiometry	en
dc.subject.other	Calculations	en
dc.title	Excess of boron in TiB2 superhard thin films: A combined experimental and ab initio study	en
heal.type	journalArticle	en
heal.identifier.primary	10.1088/0022-3727/44/38/385402	en
heal.identifier.secondary	http://dx.doi.org/10.1088/0022-3727/44/38/385402	en
heal.identifier.secondary	385402	en
heal.language	English	en
heal.publicationDate	2011	en
heal.abstract	Deviations from the nominal stoichiometry are known to affect those properties of TiB2, such as high hardness and metallic character that favour its employment in various technological applications. Here we use a combination of experimental and theoretical approaches to elucidate the dependence of B concentration on controlled growth conditions and the atomic-scale details of excess B incorporation. We find a monotonic increase in B/Ti ratio with the increase in substrate voltage during magnetron sputtering growth of nanocrystalline TiB2 films. Even for large B/Ti ratios, however, the films retain the AlB2 hexagonal structure, albeit with increased lattice constants. Using first-principles calculations we attribute these structural features to incorporation of a portion of excess B as bulk interstitials, while the remaining overstoichiometric B atoms agglomerate on B-rich surfaces of the TiB2 nanograins. The results suggest a link between observed superhardness and B presence on grain surfaces. © 2011 IOP Publishing Ltd.	en
heal.publisher	IOP PUBLISHING LTD	en
heal.journalName	Journal of Physics D: Applied Physics	en
dc.identifier.doi	10.1088/0022-3727/44/38/385402	en
dc.identifier.isi	ISI:000294772500014	en
dc.identifier.volume	44	en
dc.identifier.issue	38	en