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Effect by Doping and Surface Termination on c-BN Surface Reactivity; A Theoretical DFT Approach
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. (Oorganisk kemi)
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 19, 10061-10075 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2014. Vol. 118, no 19, 10061-10075 p.
Keyword [en]
c-BN, DFT, CVD
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-218389DOI: 10.1021/jp412695qISI: 000336198900024OAI: oai:DiVA.org:uu-218389DiVA: diva2:695532
Available from: 2014-02-11 Created: 2014-02-11 Last updated: 2017-12-06Bibliographically approved
In thesis
1. The Effect of Boron in Metal Borides and BN – A Theoretical Approach
Open this publication in new window or tab >>The Effect of Boron in Metal Borides and BN – A Theoretical Approach
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Boron, B, has many interesting electronic and structural properties, which makes it an ideal material for technical and industrial needs. The different binary materials that have been in focus in the present thesis, do all include B; metal diborides (MB2), cubic boron nitride (c-BN) forming an interface with diamond, and various phases of BN [cubic (c-BN), hexagonal (h-BN), wurtzitic (w-BN), and rhombohedral (r-BN)]. Density Functional Theory (DFT) methods have been used in studying structural geometries, energetical stabilities, electronic properties, and surface reactivity.

A structural and electronic comparison has been made for various MB2 compounds in planar and puckered structural forms. The resulting MB2 structure was found to correlate to the degree of electron transfer from the metal atom to B. A transfer of more than one electron was observed to induce a planar B structure. This is to be compared with the planar MgB2 structure, for which an electron transfer of two electrons was observed.

The initial nucleation of c-BN onto a diamond substrate has also been focused in the present thesis. This step has experimentally been found to be critical for a phase-pure c-BN thin film growth to occur. The evolution of an interfacial diamond//BN structure was investigated, with the purpose to simulate a layer-by-layer growth of c-BN. The obtained results were found to strongly support the experimental findings, in that there is a need for an extra energy in order to avoid non-cubic phases in the closest vicinity to the substrate. However, the simulations showed that it is possible to diminish this need of extra energy by completely terminating the surface by species like H or F. These calculations also showed that terminated diamond//BN generally show a stronger interfacial bond energy, thereby improving the adhesion to the diamond substrate. The importance with surface termination was not found crucial for thicker BN adlayers.

A combined effect of doping and surface termination was investigated for the various BN allotropes, (using O, C, and Si). The electron induced in c-BN by the O (or C) dopant was observed to move towards the surface B atoms, and thereby creating a more reactive surface. For the upper surface N atoms, doping was observed to create a less reactive N surface. The Si dopants did only show a positive effect on surface reactivity at the B surface sites on both h-BN (001) and r-BN (001) surfaces.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1124
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-218393 (URN)978-91-554-8879-6 (ISBN)
Public defence
2014-04-01, Häggsalen, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2014-03-10 Created: 2014-02-11 Last updated: 2014-04-29

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Pallas, AnnaLarsson, Karin

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