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Energetic stability, STM fingerprints and electronic transport properties of defects in graphene and silicene
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.ORCID iD: 0000-0002-3161-4326
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
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2016 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 8, 6702-6708 p.Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

Novel two-dimensional materials such as graphene and silicene have been heralded as possibly revolutionary in future nanoelectronics. High mobilities, and in the case of silicene, its seemingly natural integration with current electronics could make them the materials of next-generation devices. Defects in these systems, however, are unavoidable particularly in large-scale fabrication. Here we combine density functional theory and the non-equilibrium Green’s function method to simulate the structural, electronic and transport properties of different defects in graphene and silicene. We show that defects are much more easily formed in silicene, compared to graphene. We also show that, although qualitatively similar, the effects of different defects occur closer to the Dirac point in silicene, and identifying them using scanning tunneling microscopy is more difficult particularly due to buckling. This could be overcome by performing direct source/drain measurements. Finally we show that the presence of defects leads to an increase in local current from which it follows that they not only contribute to scattering, but are also a source of heating.

Place, publisher, year, edition, pages
2016. Vol. 6, no 8, 6702-6708 p.
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:uu:diva-271340DOI: 10.1039/C5RA23052GISI: 000368858000083OAI: oai:DiVA.org:uu-271340DiVA: diva2:891731
Funder
Carl Tryggers foundation Swedish Research Council, 621-2009-3628Knut and Alice Wallenberg Foundation
Available from: 2016-01-07 Created: 2016-01-07 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Influence of defects and impurities on the properties of 2D materials
Open this publication in new window or tab >>Influence of defects and impurities on the properties of 2D materials
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Graphene, the thinnest material with a stable 2D structure, is a potential alternative for silicon-based electronics. However, zero band gap of graphene causes a poor on-off ratio of current thus making it unsuitable for logic operations. This problem prompted scientists to find other suitable 2D materials. Creating vacancy defects or synthesizing hybrid 2D planar interfaces with other 2D materials, is also quite promising for modifying graphene properties. Experimental productions of these materials lead to the formation of possible defects and impurities with significant influence in device properties. Hence, a detailed understanding of the effects of impurities and defects on the properties of 2D systems is quite important.

In this thesis, detailed studies have been done on the effects of impurities and defects on graphene, hybrid graphene/h-BN and graphene/graphane structures, silicene and transition metal dichalcogenides (TMDs) by ab-initio density functional theory (DFT). We have also looked into the possibilities of realizing magnetic nanostructures, trapped at the vacancy defects in graphene, at the reconstructed edges of graphene nanoribbons, at the planar hybrid h-BN graphene structures, and in graphene/graphane interfaces. A thorough investigation of diffusion of Fe adatoms and clusters by ab-initio molecular dynamics simulations have been carried out along with the study of their magnetic properties. It has been shown that the formation of Fe clusters at the vacancy sites is quite robust. We have also demonstrated that the quasiperiodic 3D heterostructures of graphene and h-BN are more stable than their regular counterpart and certain configurations can open up a band gap. Using our extensive studies on defects, we have shown that defect states occur in the gap region of TMDs and they have a strong signature in optical absorption spectra. Defects in silicene and graphene cause an increase in scattering and hence an increase in local currents, which may be detrimental for electronic devices. Last but not the least, defects in graphene can also be used to facilitate gas sensing of molecules as well as and local site selective fluorination.  

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 100 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1432
Keyword
2D Materials, Defects on 2D materials, Impurities on 2D materials
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-300970 (URN)978-91-554-9699-9 (ISBN)
Public defence
2016-11-11, Polhemsalen Ång/10134, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
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Supervisors
Available from: 2016-10-19 Created: 2016-08-16 Last updated: 2016-11-03

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Haldar, SoumyajyotiSanyal, BiplabScheicher, Ralph.H

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