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Defect formation in graphene during low-energy ion bombardment
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
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2016 (English)In: APL Materials, ISSN 2166-532X, Vol. 4, no 4, 046104Article in journal, Letter (Refereed) Published
Abstract [en]

This letter reports on a systematic investigation of sputter induced damage in graphene caused by low energy Ar+ ion bombardment. The integral numbers of ions per area (dose) as well as their energies are varied in the range of a few eV's up to 200 eV. The defects in the graphene are correlated to the dose/energy and different mechanisms for the defect formation are presented. The energetic bombardment associated with the conventional sputter deposition process is typically in the investigated energy range. However, during sputter deposition on graphene, the energetic particle bombardment potentially disrupts the crystallinity and consequently deteriorates its properties. One purpose with the present study is therefore to demonstrate the limits and possibilities with sputter deposition of thin films on graphene and to identify energy levels necessary to obtain defect free graphene during the sputter deposition process. Another purpose is to disclose the fundamental mechanisms responsible for defect formation in graphene for the studied energy range.

Place, publisher, year, edition, pages
2016. Vol. 4, no 4, 046104
National Category
Materials Chemistry Nano Technology
URN: urn:nbn:se:uu:diva-284702DOI: 10.1063/1.4945587ISI: 000375846100007OAI: diva2:920777
Knut and Alice Wallenberg Foundation, 2011.0082Swedish Research Council, 2014-5591 2014-6463
Available from: 2016-04-19 Created: 2016-04-19 Last updated: 2016-06-30Bibliographically approved
In thesis
1. Graphene Implementation Study in Semiconductor Processing
Open this publication in new window or tab >>Graphene Implementation Study in Semiconductor Processing
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Graphene, with its two-dimensional nature and unique properties, has for over a decade captured enormous interests in both industry and academia. This work tries to answer the question of what would happen to graphene when it is subjected to various processing conditions and how this would affect the graphene functionality. The focus is placed on its ability to withstand different thin-film deposition environments with regard to the implementation of graphene in two application areas: as a diffusion barrier and in electronic devices.

With single-layer graphene films grown in-house by means of chemical vapor deposition (CVD), four techniques among the well-established thin-film deposition methods are studied in detail: atomic layer deposition (ALD), evaporation, sputter-deposition and spray-deposition. And in this order, these methods span a large range of kinetic impact energies from low to high. Graphene is known to have a threshold displacement energy of 22 eV above which carbon atoms are ejected from the lattice. Thus, ALD and evaporation work with energies below this threshold, while sputtering and spraying may involve energies above. The quality of the graphene films undergone the various depositions is mainly evaluated using Raman spectroscopy.

Spray deposition of liquid alloy Ga-In-Sn is shown to require a stack of at least 4 layers of graphene in order to act as an effective barrier to the Ga diffusion after the harsh spray-processing. Sputter-deposition is found to benefit from low substrate temperature and high chamber pressure (thereby low kinetic impact energy) so as to avoid damaging the graphene. Reactive sputtering should be avoided. Evaporation is non-invasiveness with low kinetic impact energy and graphene can be subjected to repeated evaporation and removal steps without losing its integrity. With ALD, the effects on graphene are of different nature and they are investigated in the field-effect-transistor (FET) configuration. The ALD process for deposition of Al2O3 films is found to remove undesired dopants from the prior processing and the Al2O3 films are shown to protect the graphene channel from doping by oxygen. When the substrate is turned hydrophobic by chemical treatment prior to graphene transfer-deposition, a unipolar transistor behavior is obtained.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 62 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1377
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:uu:diva-285249 (URN)978-91-554-9585-5 (ISBN)
Public defence
2016-06-10, 13:15 (English)
Available from: 2016-05-19 Created: 2016-04-19 Last updated: 2016-06-01

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Ahlberg, PatrikJohansson, FredrikZhang, ZhibinJansson, UlfZhang, Shi-LiLindblad, AndreasNyberg, Tomas
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Solid State ElectronicsDepartment of Physics and AstronomyInorganic Chemistry
Materials ChemistryNano Technology

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