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Surface engineering of SiC via sublimation etching
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0003-1000-0437
Max Lab, Lund University.
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2016 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 390, 816-822 p.Article in journal (Refereed) Published
Abstract [en]

We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10−5 mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2016. Vol. 390, 816-822 p.
National Category
Natural Sciences Materials Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-131817DOI: 10.1016/j.apsusc.2016.08.149ISI: 000385900700098OAI: oai:DiVA.org:liu-131817DiVA: diva2:1033676
Note

Funding agencies: Swedish Research Council [621-2014-5825]; Graphene Flagship [CNECT-ICT-604391]; AForsk foundation [16-576]; Swedish Foundation for Strategic Research (SSF); Knut and Allice Wallenberg Foundation

Available from: 2016-10-08 Created: 2016-10-08 Last updated: 2017-11-30Bibliographically approved
In thesis
1. Sublimation Growth of 3C-SiC: From Thick Layers to Bulk Material
Open this publication in new window or tab >>Sublimation Growth of 3C-SiC: From Thick Layers to Bulk Material
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Silicon carbide (SiC) is a semiconductor material which holds high promises for various device applications. It can be obtained in different crystal structures called polytypes. The most common ones are hexagonal (6H- and 4H-SiC) and cubic (3C-SiC) silicon carbide. The 6H- and 4H-SiC single crystal substrates are commercially available, while technologies for the growth of 3C-SiC are still under development. The unique 3C-SiC properties like isotropy, narrower bandgap (2.4 eV)  compared to hexagonal polytypes (about 3 eV) and high electron mobility make it better over hexagonal counterparts for some semiconductor applications, for example, metal oxide semiconductor field effect transistors (MOSFETs). However, due to lack of high quality material, the full potential of 3C-SiC in device applications has not been revealed. In addition, it has properties suitable to explore new concepts in efficient photovoltaics or solar driven hydrogen generation by water splitting.

There is a need for 3C-SiC seeds to grow large 3C-SiC crystals by the widely used Physical Vapor Transport (PVT) technique. In case of hexagonal SiC polytypes such seeds were produced by the Lely method during which hexagonal SiC crystals spontaneously nucleate on the inner walls of a crucible. However, the formation of 3C-SiC using the Lely method is rarely observed. Therefore, the 3C-SiC has to be heteroepitaxially grown on silicon or hexagonal SiC substrates. Silicon is an inexpensive material with very high crystalline quality. However, due to almost 20% mismatch in lattice parameters and 8% difference in thermal expansion coefficient there is a high density of structural defects formed at the 3C-SiC/Si interface. In contrast, the 3C-SiC/hexagonal SiC material system does not encounter such problems, but there are other challenges like polytype stability or formation of structural defects called double positioning boundaries (DPBs).

This thesis work mainly focuses on the growth of 3C-SiC on hexagonal SiC substrates using sublimation epitaxy. The research covers the development of growth process for thick (~1 mm) 3C-SiC layers, advancement of the growth process to eliminate DPBs and growth of bulk material using thick 3C-SiC layers as seeds. The 3C-SiC was grown on off-oriented hexagonal SiC substrates. The surfaces of such substrates contain high density of steps. Therefore, they have mostly been used for the growth of homoepitaxial hexagonal layers or bulk crystals via step flow mechanism. However, as demonstrated in this thesis, under special conditions the 3C-SiC with high crystalline quality can also be grown on off-oriented hexagonal substrates. The stability window for the growth of hexagonal and cubic polytypes on nominally on-axis hexagonal SiC substrates is also explored. Moreover, it is demonstrated how the temperature profile inside the graphite crucible is influenced by the change in thermal insulation properties and how such change results in enhanced polytype stability during the growth of thick SiC layers. In addition, different sources for sublimation epitaxial growth of doped SiC layers were analyzed to gain further understanding of new parameter windows.

As a part of this thesis, a sublimation etching of 6H-, 4H- and 3C-SiC polytypes is presented using two different etching arrangements in vacuum (10-5 mbar) and Ar ambient. It is demonstrated that this technique can be used to remove residual scratches on the surface as well as to obtain various surface step structures which could be used for the growth of graphene nanostructures.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 45 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1760
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127802 (URN)978-91-7685-778-6 (ISBN)
Public defence
2016-06-09, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
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Available from: 2016-05-13 Created: 2016-05-13 Last updated: 2016-11-23Bibliographically approved

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Jokubavicius, ValdasYazdi, GholamrezaIvanov, Ivan G.Lakimov, TihomirSyväjärvi, MikaelYakimova, Rositsa
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