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Theoretical Investigations of Boron Related Materials Using DFT
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In the history of Chemistry, materials chemists have developed their ideas mainly by doing experiments in laboratories. The underlying motivation for this laboratory work has generally been pure curiosity or the ambition to find a solution to a specific problem. Minor changes in the composition or structure of a material can cause major changes in its properties. The development of powerful computers has now opened up the possibility to calculate properties of new materials using quantum mechanical methods.

The Chemistry of different boron-related materials has been evaluated in this thesis by Density Functional Theory (DFT). Cubic boron nitride (c-BN) is a most interesting material for the microelectronics and tool industry. During thin film deposition of c-BN, several problems arise which most often result in unwanted BN isomorphs. Chemical processes at the (110) and (111) surface of c-BN have been investigated in order to shed light upon some of these complex processes. Typically adsorption energies and surface reconstruction were found to differ significantly between the two surfaces.

Other materials investigated are layered transition-metal diborides (MeB2). Incorporation of transition-metal atoms into elemental boron in its most fundamental structure, ά-boron, has also been investigated. The calculations on MeB2 focused on the stability of the planar compared to the puckered structure of MeB2. Stability was investigated by calculating Density of States (DOS) and bond populations. Deviations in the cell parameters from their ideal values were also considered.

A separate project concerned reactivity of the TiB2(001) surface. Molecular and dissociated adsorption energies and adsorption geometries were calculated for H2, H2O and O2. It was concluded that the titanium surface was more reactive than the boron surface and that the adsorption energies were comparable to or stronger than other well known surface-active compounds like TiO2.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis , 2007. , s. 48
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 309
Nyckelord [en]
Inorganic chemistry, boron nitride, density functional theory, chemical vapour deposition, atomic layer deposition, surface reactivity, adsorption, abstraction, computational chemistry
Nyckelord [sv]
Oorganisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-7889ISBN: 978-91-554-6895-8 (tryckt)OAI: oai:DiVA.org:uu-7889DiVA, id: diva2:170275
Disputation
2007-05-16, Siegbahnsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15
Opponent
Handledare
Tillgänglig från: 2007-04-25 Skapad: 2007-04-25Bibliografiskt granskad
Delarbeten
1. Solid solutions of 3d-metal atoms in boron icosahedra, a structural and energetic investigation
Öppna denna publikation i ny flik eller fönster >>Solid solutions of 3d-metal atoms in boron icosahedra, a structural and energetic investigation
Manuskript (Övrigt vetenskapligt)
Identifikatorer
urn:nbn:se:uu:diva-95897 (URN)
Tillgänglig från: 2007-04-25 Skapad: 2007-04-25 Senast uppdaterad: 2010-01-13Bibliografiskt granskad
2. Adsorption of H, NHx, BHx and BBrx on a (110) surface of c-BN: A quantum-mechanical DFT study
Öppna denna publikation i ny flik eller fönster >>Adsorption of H, NHx, BHx and BBrx on a (110) surface of c-BN: A quantum-mechanical DFT study
2007 (Engelska)Ingår i: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 16, nr 1, s. 131-137Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The adsorption of H, NHx, BHx and BBrx (x = 1, 2 and 3) on hydrogen-terminated (110) surfaces of c-BN has been investigated theoretically. Density Functional Theory (DFT) methods were used in order to study the adsorption processes of these different species on both nitrogen and boron sites at the surfaces. With one exception, all adsorption processes were found to be exothermic and in the order; BBr·  BH2· ≈H· > BH·  NH· ≈ BBr2· > NH2·  BH3· > NH3· > BBr3· for a nitrogen site, and NH2· > NH· > BBr· > H· > BH· > BH2· ≈ BBr2·  BBr3· ≈ NH3· ≈BH3· for a boron site. The exception was NH3 being bonded to a surface N site, for which the reaction was slightly endothermic. The various modeling parameters that were used in the calculations of these adsorption energies have been chosen by performing series of extensive test calculations, in which the effect of these parameters (e.g. template size, vacuum depth, atom constraints) on bond-strength have been carefully estimated. Moreover, a semi-empirical method has been evaluated with the purpose to study the usefulness of this type of method for the polar BN compound.

Nyckelord
DFT, Boron nitride, Adsorption, ALD
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:uu:diva-95898 (URN)10.1016/j.diamond.2006.04.015 (DOI)000243618000019 ()
Tillgänglig från: 2007-04-25 Skapad: 2007-04-25 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
3. Influence of Surface Terminating H and F on Structural c-BN Collapse
Öppna denna publikation i ny flik eller fönster >>Influence of Surface Terminating H and F on Structural c-BN Collapse
Ingår i: Thin Solid FilmsArtikel i tidskrift (Refereegranskat) Submitted
Identifikatorer
urn:nbn:se:uu:diva-95899 (URN)
Tillgänglig från: 2007-04-25 Skapad: 2007-04-25Bibliografiskt granskad
4. Relative Stability Between Planar and Puckered Structures of 3d Metal Diborides: A Quantum Mechanical Study
Öppna denna publikation i ny flik eller fönster >>Relative Stability Between Planar and Puckered Structures of 3d Metal Diborides: A Quantum Mechanical Study
2007 (Engelska)Ingår i: Journal of Physical ChemistryArtikel i tidskrift (Refereegranskat) In press
Identifikatorer
urn:nbn:se:uu:diva-95900 (URN)
Tillgänglig från: 2007-04-25 Skapad: 2007-04-25 Senast uppdaterad: 2014-01-24Bibliografiskt granskad
5. Reactivity of TiB2(001); adsorption studies of H2, H2O and O2
Öppna denna publikation i ny flik eller fönster >>Reactivity of TiB2(001); adsorption studies of H2, H2O and O2
Ingår i: Surface ScienceArtikel i tidskrift (Refereegranskat) Submitted
Identifikatorer
urn:nbn:se:uu:diva-95901 (URN)
Tillgänglig från: 2007-04-25 Skapad: 2007-04-25Bibliografiskt granskad

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