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Chemical Vapour Deposition of sp2 Hybridised Boron Nitride
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this work was to develop a chemical vapour deposition process and understand the growth of sp2 hybridised Boron Nitride (sp2-BN). Thus, the growth on different substrates together with the variation of growth parameters was investigated in details and is presented in the papers included in this thesis. Deposited films of sp2-BN were characterised with the purpose to determine optimal deposition process parameters for the growth of high crystal quality thin films with further investigations of chemical composition, morphology and other properties important for the implementation of this material towards electronic, optoelectronic devices and devices based on graphene/BN heterostructures.

For the growth of sp2-BN triethyl boron and ammonia were employed as B and N precursors, respectively. Pure H2 as carrier gas is found to be necessary for the growth of crystalline sp2-BN. Addition of small amount of silane to the gas mixture improves the crystalline quality of the growing sp2-BN film.

It was observed that for the growth of crystalline sp2-BN on c-axis oriented α-Al2O3 a thin and strained AlN buffer layer is needed to support epitaxial growth of sp2-BN, while it was possible to deposit rhombohedral BN (r-BN) on various polytypes of SiC without the need for a buffer layer. The growth temperature suitable for the growth of  crystalline sp2-BN is 1500 °C. Nevertheless, the growth of crystalline sp2-BN was also observed on α-Al2O3 with an AlN buffer layer at a lower temperature of 1200 °C. Growth at this low temperature was found to be hardly controllable due to the low amount of Si that is necessary at this temperature and its accumulation in the reaction cell. When SiC was used as a substrate at the growth temperature of 1200 °C, no crystalline sp2-BN was formed, according to X-ray diffraction.

Crystalline structure investigations of the deposited films showed formation of twinned r-BN on both substrates used. Additionally, it was found that the growth on α-Al2O3 with an AlN buffer layer starts with the formation of hexagonal BN (h-BN) for a thickness of around 4 nm. The formation of h-BN was observed at growth temperatures of 1200 °C and 1500 °C on α-Al2O3 with AlN buffer layer while there were no traces of h-BN found in the films deposited on SiC substrates in the temperature range between 1200 °C and 1700 °C. As an explanation for such growth behaviour, reproduction of the substrate crystal stacking is suggested.  Nucleation and growth mechanism are investigated and presented in the papers included in this thesis.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 54 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1632
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-112580DOI: 10.3384/diss.diva-112580ISBN: 978-91-7519-193-5 (print)OAI: oai:DiVA.org:liu-112580DiVA: diva2:768471
Public defence
2015-02-10, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2015-03-11Bibliographically approved
List of papers
1. Epitaxial CVD growthof sp2-hybridized boron nitrideusing aluminum nitride as buffer layer
Open this publication in new window or tab >>Epitaxial CVD growthof sp2-hybridized boron nitrideusing aluminum nitride as buffer layer
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2011 (English)In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 5, no 10-11, 397-399 p.Article in journal (Refereed) Published
Abstract [en]

Epitaxial growth of sp2-hybridized boron nitride (BN) using chemical vapour deposition, with ammonia and triethyl boron as precursors, is enabled on sapphire by introducing an aluminium nitride (AlN) buffer layer. This buffer layer is formed by initial nitridation of the substrate. Epitaxial growth is verified by X-ray diffraction measurements in Bragg–Brentano configuration, pole figure measurements and transmission electron microscopy. The in-plane stretching vibration of sp2-hybridized BN is observed at 1366 cm–1 from Raman spectroscopy. Time-of-flight elastic recoil detection analysis confirms almost perfect stoichiometric BN with low concentration of carbon, oxygen and hydrogen contaminations.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2011
Keyword
chemical vapor deposition;BN;epitaxy;X-ray diffraction
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-73160 (URN)10.1002/pssr.201105410 (DOI)000297747600014 ()
Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2017-12-08
2. Growth of High Quality Epitaxial Rhombohedral Boron Nitride
Open this publication in new window or tab >>Growth of High Quality Epitaxial Rhombohedral Boron Nitride
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2012 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 12, no 6, 3215-3220 p.Article in journal (Refereed) Published
Abstract [en]

Epitaxial growth of sp(2)-hybridized boron nitride (sp(2) BN) films on sapphire substrates is demonstrated in a hot wall chemical vapor deposition reactor at the temperature of 1500 degrees C, using triethyl boron and ammonia as precursors. The influence of the main important process parameters, temperature, N/B ratio, B/H-2 ratio, and carrier gas composition on the quality of the grown layers is investigated in detail. X-ray diffraction shows that epitaxial rhombohedral BN (r-BN) film can be deposited only in a narrow process parameter window; outside this window either turbostratic-BN or amorphous BN is favored if BN is formed. In addition, a thin strained AlN buffer layer is needed to support epitaxial growth of r-BN film on sapphire since only turbostratic BN is formed on sapphire substrate. The quality of the grown film is also affected by the B/H-2 ratio as seen from a change of the spacing between the basal planes as revealed by X-ray diffraction. Time-of-flight elastic recoil detection analysis shows an enhancement of the C and O impurities incorporation at lower growth temperatures. The gas phase chemistry for the deposition is discussed as well as the impact of the growth rate on the quality of the BN film.

Place, publisher, year, edition, pages
American Chemical Society, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-79095 (URN)10.1021/cg300364y (DOI)000304838000062 ()
Note

Funding Agencies|Swedish Research Council|VR 621-2009-5264VR 622-2008-1247|

Available from: 2012-06-29 Created: 2012-06-29 Last updated: 2017-12-07
3. On the effect of silicon in CVD of sp2 hybridized boron nitride thin films
Open this publication in new window or tab >>On the effect of silicon in CVD of sp2 hybridized boron nitride thin films
2013 (English)In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 15, no 3, 455-458 p.Article in journal (Refereed) Published
Abstract [en]

The influence of silicon on the growth of epitaxial rhombohedral boron nitride (r-BN) films deposited on sapphire (0001) by chemical vapor deposition is investigated. X-ray diffraction measurements and secondary ion mass spectrometry show that silicon favors the formation of r-BN and is incorporated into the film.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-87243 (URN)10.1039/c2ce26423d (DOI)000312197600006 ()
Note

Funding Agencies|Swedish Research Council|VR 621-2009-5264VR 622-2008-1247|

Available from: 2013-01-14 Created: 2013-01-14 Last updated: 2017-12-06
4. Chemical vapour deposition of epitaxial rhombohedral BN thin films on SiC substrates
Open this publication in new window or tab >>Chemical vapour deposition of epitaxial rhombohedral BN thin films on SiC substrates
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2014 (English)In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 16, no 24, 5430-5436 p.Article in journal (Refereed) Published
Abstract [en]

Epitaxial growth of rhombohedral boron nitride (r-BN) on different polytypes of silicon carbide (SiC) is demonstrated using thermally activated hot-wall chemical vapour deposition and triethyl boron and ammonia as precursors. With respect to the crystalline quality of the r-BN films, we investigate the influence of the deposition temperature, the precursor ratio (N/B) and the addition of a minute amount of silicon to the gas mixture. From X-ray diffraction and transmission electron microscopy, we find that the optimal growth temperature for epitaxial r-BN on the Si-face of the SiC substrates is 1500 degrees C at a N/B ratio of 642 and silicon needs to be present not only in the gas mixture during deposition but also on the substrate surface. Such conditions result in the growth of films with a c-axis identical to that of the bulk material and a thickness of 200 nm, which is promising for the development of BN films for electronic applications.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2014
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-108816 (URN)10.1039/c4ce00381k (DOI)000336839900032 ()
Available from: 2014-07-07 Created: 2014-07-06 Last updated: 2017-12-05
5. Polytype pure sp2-BN thin films as dictated by the substrate crystal structure
Open this publication in new window or tab >>Polytype pure sp2-BN thin films as dictated by the substrate crystal structure
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2015 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 27, no 5, 1640-1645 p.Article in journal (Refereed) Published
Abstract [en]

Boron nitride (BN) is a promising semiconductor material, but its current exploration is hampered by difficulties in growth of single crystalline phase-pure thin films. We compare the growth of sp2-BN by chemical vapor deposition on (0001) 6H-SiC and on (0001) α-Al2O3 substrates with an AlN buffer layer. Polytype-pure rhombohedral BN (r-BN) with a thickness of 200 nm is observed on SiC whereas hexagonal BN (h-BN) nucleates and grows on the AlN buffer layer. For the latter case after a thickness of 4 nm, the h-BN growth is followed by r-BN growth to a total thickness of 200 nm. We find that the polytype of the sp2-BN films is determined by the ordering of Si-C or Al-N atomic pairs in the underlying crystalline structure (SiC or AlN). In the latter case the change from h-BN to r-BN is triggered by stress relaxation. This is important for the development of BN semiconductor device technology.

Place, publisher, year, edition, pages
Washington: American Chemical Society (ACS), 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112577 (URN)10.1021/cm5043815 (DOI)000350919000025 ()
Note

This work was supported by the Swedish Research Council (VR, Grant 621-2013-5585), Carl Tryggers Foundation (No. 12:175), and the CeNano program at Linkoping University. H.H. acknowledges support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU No. 2009-00971). Z.C. acknowledges the support of the Bolyai Janos research scholarship of the Hungarian Academy of Sciences. The Knut and Alice Wallenberg (KAW) Foundation is acknowledged for the Electron Microscope Laboratory in Linkoping. Sven G. Andersson is gratefully acknowledged for his technical support of the growth activities.

Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2017-12-05Bibliographically approved
6. Nucleation and initial growth of sp2-BNon α-Al2O3 and SiC by chemical vapour deposition
Open this publication in new window or tab >>Nucleation and initial growth of sp2-BNon α-Al2O3 and SiC by chemical vapour deposition
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2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Knowledge on thin films evolution from the early stages of growth is important for the control of quality and properties of the film. Here we present study of the early growth stages and evolution of the crystalline structure of sp2 hybridised Boron Nitride (BN) thin films deposited by chemical vapour deposition from triethyl boron and ammonia. Nucleation of hexagonal BN (h-BN) is observed already at 1200 °C on α-Al2O3 substrate with an AlN buffer layer (AlN/α-Al2O3) while no formation of h-BN is detected when the growth is done on 6H-SiC in a growth temperature range between 1200 °C and 1700 °C. We demonstrate that h-BN grows on AlN/α-Al2O3 exhibiting a layer-by-layer growth mode up to ca. 4 nm followed by a transition to r-BN growth when grown at 1500 °C. The following r-BN growth is suggested to proceed with mixed layer-by-layer and island growth mode; after a thin continuous layer of r-BN, islands formation is favoured leading to a twinned r-BN structure of the film. We find that h-BN does not grow on 6H-SiC substrates instead r-BN nucleates and grows directly as a twinned crystal. The twinning is found to be suppressed by a surface preparation of the SiC substrate with SiH4 prior to BN growth. These results open up for a more controlled epitaxial growth of sp2-BN for future electronic applications.

National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112578 (URN)
Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2015-03-11Bibliographically approved

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