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Karlsson, L., Birch, J., Mockuté, A., Sigurdur Ingason, A., Ta, H. Q., Rummeli, M. H., . . . Persson, P. O. Å. (2016). Residue reduction and intersurface interaction on single graphene sheets. Carbon, 100, 345-350
Open this publication in new window or tab >>Residue reduction and intersurface interaction on single graphene sheets
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2016 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 100, p. 345-350Article in journal (Refereed) Published
Abstract [en]

Large regions of pristine graphene are essential to applications which rely on the ideal graphene properties. Common methods for transferring chemical vapour deposition grown graphene to suitable substrates leaves metal oxide particles and poly(methyl methacrylate) (PMMA) residues on opposing surfaces, which degrade the properties. A common method to reduce the residues include annealing in vacuum or in argon, however, residues remain on the graphene sheet. The present investigation reports on the metal oxide particle ripening and PMMA decomposition on a single graphene sheet during in-situ annealing up to 1300 degrees C in a transmission electron microscope. It is shown that the PMMA residues are increasingly reduced at elevated temperatures although the reduction is strongly correlated to the metal oxide particle coverage on the opposing graphene surface. This is shown to occur as a consequence of an electrostatic interaction between the residues and that this prevents the establishment of large clean areas. (C) 2016 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Pergamon Press, 2016
National Category
Physical Sciences
urn:nbn:se:liu:diva-126123 (URN)10.1016/j.carbon.2016.01.007 (DOI)000369961400040 ()

Funding Agencies|Swedish Research Council [621-2012-4359, 622-2008-405, 642-2013-8020]; Olle Engkvist foundation; Knut and Alice Wallenbergs Foundation; European Research Council [258509]; IBS Korea [IBS-RO11-D1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]

Available from: 2016-03-15 Created: 2016-03-15 Last updated: 2017-11-30Bibliographically approved
Karlsson, L. (2016). Transmission Electron Microscopy of 2D Materials: Structure and Surface Properties. (Doctoral dissertation). Linköping University Electronic Press
Open this publication in new window or tab >>Transmission Electron Microscopy of 2D Materials: Structure and Surface Properties
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During recent years, new types of materials have been discovered with unique properties. One family of such materials are two-dimensional materials, which include graphene and MXene. These materials are stronger, more flexible, and have higher conductivity than other materials. As such they are highly interesting for new applications, e.g. specialized in vivo drug delivery systems, hydrogen storage, or as replacements of common materials in e.g. batteries, bulletproof clothing, and sensors. The list of potential applications is long for these new materials.

As these materials are almost entirely made up of surfaces, their properties are strongly influenced by interaction between their surfaces, as well as with molecules or adatoms attached to the surfaces (surface groups). This interaction can change the materials and their properties, and it is therefore imperative to understand the underlying mechanisms. Surface groups on two-dimensional materials can be studied by Transmission Electron Microscopy (TEM), where high energy electrons are transmitted through a sample and the resulting image is recorded. However, the high energy needed to get enough resolution to observe single atoms damages the sample and limits the type of materials which can be analyzed. Lowering the electron energy decreases the damage, but the image resolution at such conditions is severely limited by inherent imperfections (aberrations) in the TEM. During the last years, new TEM models have been developed which employ a low acceleration voltage together with aberration correction, enabling imaging at the atomic scale without damaging the samples. These aberration-corrected TEMs are important tools in understanding the structure and chemistry of two-dimensional materials.

In this thesis the two-dimensional materials graphene and Ti3C2Tx MXene have been investigated by low-voltage, aberration-corrected (scanning) TEM. High temperature annealing of graphene covered by residues from the synthesis is studied, as well as the structure and surface groups on single and double Ti3C2Tx MXene. These results are important contributions to the understanding of this class of materials and how their properties can be controlled.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2016. p. 86
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1745
Transmission Electron Microscopy, Two-dimensional materials, Graphene, MXene, Ti3C2Tx, Low-voltage TEM, Aberration-corrected TEM, monchromated TEM, Scanning transmission electron microscopy, Electron energy loss spectroscopy
National Category
Condensed Matter Physics Nano Technology
urn:nbn:se:liu:diva-127526 (URN)10.3384/diss.diva-127526 (DOI)978-91-7685-832-5 (ISBN)
Public defence
2016-06-15, Planck, Fysikhuset, Campus Valla, Linköping, 09:15 (English)
Swedish Research Council, 621-2012-4359Swedish Research Council, 622-2008-405Swedish Research Council, 642-2013-8020Swedish Research Council, 621-2009-5294
Available from: 2016-05-23 Created: 2016-05-02 Last updated: 2016-05-23Bibliographically approved
Karlsson, L., Birch, J., Halim, J., Barsoum, M. W. & Persson, P. (2015). Atomically Resolved Structural and Chemical Investigation of Single MXene Sheets. Nano letters (Print), 15(8), 4955-4960
Open this publication in new window or tab >>Atomically Resolved Structural and Chemical Investigation of Single MXene Sheets
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2015 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 8, p. 4955-4960Article in journal (Refereed) Published
Abstract [en]

The properties of two-dimensional (2D) materials depend strongly on the chemical and electrochemical activity of their surfaces. MXene, one of the most recent additions to 2D materials, shows great promise as an energy storage material. In the present investigation, the chemical and structural properties of individual Ti3C2 MXene sheets with associated surface groups are investigated at the atomic level by aberration corrected STEM-EELS. The MXene sheets are shown to exhibit a nonuniform coverage of O-based surface groups which locally affect the chemistry. Additionally, native point defects which are proposed to affect the local surface chemistry, such as oxidized titanium adatoms (TiOx), are identified and found to be mobile.

MXene, Ti3C2Tx, Aberration corrected STEM, Surface Chemistry, Surface
National Category
Condensed Matter Physics
urn:nbn:se:liu:diva-120927 (URN)10.1021/acs.nanolett.5b00737 (DOI)000359613700017 ()26177010 (PubMedID)
Available from: 2015-08-31 Created: 2015-08-31 Last updated: 2017-12-04Bibliographically approved
Mendoza, A., Arreola-Jardón, G., Karlsson, L., Persson, P. & Jiménez-Sandoval, S. (2014). Optical properties of CuCdTeO thin films sputtered from CdTe-CuO composite targets. Paper presented at 6th International Conference on Spectroscopic Ellipsometry (ICSE-VI), May 26–31, 2013, Kyoto, Japan. Thin Solid Films, 571, 706-711
Open this publication in new window or tab >>Optical properties of CuCdTeO thin films sputtered from CdTe-CuO composite targets
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2014 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 571, p. 706-711Article in journal (Refereed) Published
Abstract [en]

The effective complex dielectric function (ε) of Cu and O containing CdTe thin films is reported in the spectral range of 0.05 to 6 eV. The films were fabricated by rf sputtering from targets comprised by a mixture of CdTe and CuO powders with nominal Cu and O concentrations in the range of 2–10 at.%. Low concentration levels improved the crystalline quality of the films. Spectroscopic ellipsometry and transmittance measurements were used to determine ε. The critical point energies E1, E11, and E2 of CdTe are red-shifted with the incorporation of Cu and O. Also, an absorption band is developed in the infrared range which is associated with a mixture of CdTe and low resistivity phases Cu2 − xTe according to an effective medium analysis. The elemental distribution of the films was mapped by energy dispersive X-ray spectroscopy using scanning transmission electron microscopy.

Place, publisher, year, edition, pages
Elsevier, 2014
National Category
Condensed Matter Physics
urn:nbn:se:liu:diva-112740 (URN)10.1016/j.tsf.2014.01.042 (DOI)000346055200070 ()
6th International Conference on Spectroscopic Ellipsometry (ICSE-VI), May 26–31, 2013, Kyoto, Japan
Available from: 2014-12-10 Created: 2014-12-10 Last updated: 2017-12-05Bibliographically approved

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