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Nanostructured carbon-based thin films: prediction and design
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-9464-5111
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbon-based thin films are a vast group of materials of great technological importance. Thanks to the different bonding options for carbon, a large variety of structures (from amorphous to nanostructured) can be achieved in the process of film synthesis. The structural diversity increases even more if carbon is combined with relatively small quantities of atoms of other elements. This results in a set of materials with many different interesting properties for a wide range of technological applications.

This doctoral thesis is about nanostructured carbon-based thin films. In particular, the focus is set on theoretical modeling, prediction of structural features and design of sulfo carbide (CSx) and carbon fluoride (CFx) thin films.

The theoretical approach follows the synthetic growth concept (SGC) which is based on the density functional theory. The SGC departure point is the fact that the nanostructured films of interest can be modeled as assemblies of low dimensional units (e.g., finite graphene-like model systems), similarly to modeling graphite as stacks of graphene sheets. Moreover, the SGC includes a description of the groups of atoms that act as building blocks (i.e., precursors) during film deposition, as well as their interaction with the growing film.

This thesis consists of two main parts:

Prediction: In this work, I show that nanostructured CSx thin films can be expected for sulfur contents up to 20 atomic % with structural characteristics that go from graphite-like to fullerene-like (FL). In the case of CFx thin films, a diversity of structures are predicted depending on the fluorine concentration. Short range ordered structures, such as FL structure, can be expected for low concentrations (up to 5 atomic %). For increasing fluorine concentration, diamond-like and polymeric structures should predominate. As a special case, I also studied the ternary system CSxFy. The calculations show that CSxFy thin films with nanostructured features should be possible to synthesize at low sulfur and fluorine concentrations and the structural characteristics can be described and explained in terms of the binaries CSx and CFx.

Design: The carbon-based thin films predicted in this thesis were synthesized by magnetron sputtering. The results from my calculations regarding structure and composition, and analysis of precursors (availability and role during deposition process) were successfully combined with the experimental techniques in the quest of obtaining films with desired structural features and understanding their properties.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. , 79 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1696
Keyword [en]
carbon, carbon-based, thin films, fullerene-like, modeling, dft
National Category
Condensed Matter Physics Nano Technology
Identifiers
URN: urn:nbn:se:liu:diva-121021DOI: 10.3384/diss.diva-121021ISBN: 978-91-7685-976-6 (print)OAI: oai:DiVA.org:liu-121021DiVA: diva2:850939
Public defence
2015-10-16, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2015-09-04 Created: 2015-09-02 Last updated: 2016-08-31Bibliographically approved
List of papers
1. Fullerene-like CSx: A first-principles study of synthetic growth
Open this publication in new window or tab >>Fullerene-like CSx: A first-principles study of synthetic growth
2011 (English)In: CHEMICAL PHYSICS LETTERS, ISSN 0009-2614, Vol. 506, no 1-3, 86-91 p.Article in journal (Refereed) Published
Abstract [en]

Fullerene-Like (FL) Sulpho-Carbide (CSx) compounds have been addressed by first principles calculations. Geometry optimization and cohesive energy results are presented for the relative stability of precursor species such as C2S, CS2, and C2S2 in isolated form. The energy cost for structural defects, arising from the substitution of C by S is also reported. Similar to previously synthesized FL-CNx and FL-CPx compounds, the pentagon, the double pentagon defects as well as the Stone-Wales defects are confirmed as energetically feasible in CSx compounds.

Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-67563 (URN)10.1016/j.cplett.2011.02.059 (DOI)000288987600016 ()
Note
Original Publication: Cecilia Goyenola, Gueorgui Kostov Gueorguiev, Sven Stafström and Lars Hultman, Fullerene-like CSx: A first-principles study of synthetic growth, 2011, CHEMICAL PHYSICS LETTERS, (506), 1-3, 86-91. http://dx.doi.org/10.1016/j.cplett.2011.02.059 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2011-04-18 Created: 2011-04-18 Last updated: 2017-05-05
2. Structural Patterns Arising during Synthetic Growth of Fullerene-Like Sulfocarbide
Open this publication in new window or tab >>Structural Patterns Arising during Synthetic Growth of Fullerene-Like Sulfocarbide
2012 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 39, 21124-21131 p.Article in journal (Refereed) Published
Abstract [en]

Carbon-based fullerene-like (FL) solid compounds are a new class of materials with extraordinary mechanical properties, which can be tuned by the dopant choice and its concentration. In this work, FL sulfocarbide (CSx) was studied by DFT simulations during synthetic growth with CmSn (m, n andlt;= 2). The energetic and structural effects of S atoms at C sites in a graphene-like network were addressed by geometry optimizations and cohesive energy calculations. Results showed that for S concentrations lower than 10 at. %, smoothly bent pure hexagonal networks predominate. For higher S concentrations, the higher defect concentration leads to stronger deformation of the graphene-like sheets. It was determined that FL-CSx is well-structured (not amorphous) for S contents between 10 and 20 at. %. In contrast to other FL materials, bond rotation mechanisms are not expected to play any significant role during FL-CSx formation, and cross-linking sites are less frequent and may be assimilated in the planar structure during growth. Both quasi-planar networks and cage-like conformations were found to form during the synthetic growth of CSx. The detailed analysis of how CSx structural patterns form during its synthetic growth provides a realistic picture for the deposition of this novel compound by magnetron sputtering.

Place, publisher, year, edition, pages
American Chemical Society, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-84738 (URN)10.1021/jp307347t (DOI)000309375700061 ()
Note

Funding Agencies|Swedish Research Council (VR)||VR||

Available from: 2012-10-19 Created: 2012-10-19 Last updated: 2017-12-07
3. CF(x): A first-principles study of structural patterns arising during synthetic growth
Open this publication in new window or tab >>CF(x): A first-principles study of structural patterns arising during synthetic growth
2011 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 516, no 1-3, 62-67 p.Article in journal (Refereed) Published
Abstract [en]

Structural and bonding patterns arising from the incorporation of fluorine atoms in a graphene-like network relevant to the deposition of carbon fluoride (CF(x)) films were addressed by first-principles calculations. We find that large N-member (N = 8-12) rings, defects by sheet branching, and defects associated with bond rotation pertain to CF(x). The cohesive energy gains associated with these patterns are similar to 0.2-0.4 eV/at., which is similar to those for a wide range of defects in other C-based nanostructured solids. Fullerene-like CF(x) is predicted for F concentrations below similar to 10 at.%, while CF(x) compounds with higher F content are predominantly amorphous or polymeric.

Place, publisher, year, edition, pages
Elsevier, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-72251 (URN)10.1016/j.cplett.2011.09.045 (DOI)000296582400011 ()
Note

Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA)||European Research Council (ERC)||

Available from: 2011-11-24 Created: 2011-11-24 Last updated: 2017-12-08
4. CF(x) thin solid films deposited by high power impulse magnetron sputtering: Synthesis and characterization
Open this publication in new window or tab >>CF(x) thin solid films deposited by high power impulse magnetron sputtering: Synthesis and characterization
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2011 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 4, 646-653 p.Article in journal (Refereed) Published
Abstract [en]

Fluorine containing amorphous carbon films (CF(x), 0.16 andlt;= x andlt;= 0.35) have been synthesized by reactive high power impulse magnetron sputtering (HiPIMS) in an Ar/CF(4) atmosphere. The fluorine content of the films was controlled by varying the CF(4) partial pressure from 0 mPa to 110 mPa at a constant deposition pressure of 400 mPa and a substrate temperature of 110 degrees C. The films were characterized regarding their composition, chemical bonding and microstructure as well as mechanical properties by applying elastic recoil detection analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and nanoindentation. First-principles calculations were carried out to predict and explain F-containing carbon thin film synthesis and properties. By geometry optimizations and cohesive energy calculations the relative stability of precursor species including C(2), F(2) and radicals, resulting from dissociation of CF4, were established. Furthermore, structural defects, arising from the incorporation of F atoms in a graphene-like network, were evaluated. All as-deposited CF(x) films are amorphous. Results from X-ray photoelectron spectroscopy and Raman spectroscopy indicate a graphitic nature of CF(x) films with x andlt;= 0.23 and a polymeric structure for films with x andgt;= 0.26. Nanoindentation reveals hardnesses between similar to 1 GPa and similar to 16 GPa and an elastic recovery of up to 98%.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
Fluorine containing carbon thin films, HiPIMS, CF(x), First principle calculations, XPS, TEM
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-72809 (URN)10.1016/j.surfcoat.2011.06.055 (DOI)000297086700011 ()
Note

Funding Agencies|Hungarian Academy of Sciences||

Available from: 2011-12-09 Created: 2011-12-08 Last updated: 2017-12-08
5. Reactive High Power Impulse Magnetron Sputtering of CFx Thin Films in Mixed Ar/CF4 and Ar/C4F8 Discharges
Open this publication in new window or tab >>Reactive High Power Impulse Magnetron Sputtering of CFx Thin Films in Mixed Ar/CF4 and Ar/C4F8 Discharges
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The reactive high power impulse magnetron sputtering (HiPIMS) processes of C in Ar/tetrafluoromethane CF4 and Ar/octafluorocyclobutane (c-C4F8) have been characterized. Amorphous carbon fluoride (CFx) films were synthesized at deposition pressure and substrate temperature of 400 mPa and 110 oC, respectively. The CFx film composition was controlled in the range of 0.15 < x < 0.35 by varying the partial pressure of the F-containing gases from 0 mPa to 110 mPa. The reactive plasma was studied employing time averaged positive ion mass spectrometry and the resulting thin films were characterized regarding their composition, chemical bonding and microstructure as well as mechanical properties by elastic recoil detection analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation, and water droplet contact angle measurements, respectively. The experimental results were compared to results obtained by first-principles calculations based on density functional theory.

The modeling of the most abundant precursor fragment from the dissociation of CF4 and C4F8 provided their relative stability, abundance, and reactivity, thus permitting to evaluate the role of each precursor during film growth. Positive ion mass spectrometry of both F plasmas show an abundance of CF+, C+, CF⁺₂, and CF⁺₃ (in this order) as corroborated by first-principles calculations. Only CF⁺₃ exceeded the Ar+ signal in a CF4 plasma. Two deposition regimes are found depending on the partial pressure of the F-containing reactive gas, where films with fluorine contents below 24 at% exhibit a graphitic nature, whereas a polymeric structure applies to films with fluorine contents exceeding 27 at%. Moreover, abundant precursors in the plasma are correlated to the mechanical response of the different CFx thin films. The decreasing hardness with increasing F content can be attributed to the abundance of CF⁺₃ precursor species, weakening the C matrix.

Keyword
c-C4F8, CF4, fluorine containing carbon thin films, HiPIMS, CFx, first principle calculations, XPS, TEM, positive ion mass spectrometry
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-90908 (URN)
Available from: 2013-04-08 Created: 2013-04-08 Last updated: 2017-05-05Bibliographically approved
6. Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles
Open this publication in new window or tab >>Carbon Fluoride, CFx: Structural Diversity as Predicted by First Principles
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2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 12, 6514-6521 p.Article in journal (Refereed) Published
Abstract [en]

Fluorinated carbon-based thin films offer a wide range of properties for many technological applications that depend on the microstructure of the films. To gain a better understanding of the role of fluorine in the structural formation of these films, CFx systems based on graphene-like fragments were studied by first-principles calculations. Generally, the F concentration determines the type of film that can be obtained. For low F concentrations (up to similar to 5 at. %), films with fullerene-like as well as graphite-like features are expected. Larger F concentrations (greater than= 10 at. %) give rise to increasingly amorphous carbon films. Further increasing the F concentration in the films leads to formation of a polymer-like microstructure. To aid the characterization of CFx systems generated by computational methods, a statistical approach is developed.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-106285 (URN)10.1021/jp500653c (DOI)000333578300060 ()
Available from: 2014-05-06 Created: 2014-05-05 Last updated: 2017-12-05Bibliographically approved
7. Theoretical prediction and synthesis of CSxFy thin films
Open this publication in new window or tab >>Theoretical prediction and synthesis of CSxFy thin films
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 17, 9527-9534 p.Article in journal (Refereed) Published
Abstract [en]

A new carbon-based compound: CSxFy was addressed by density functional theory calculations and synthesized by reactive magnetron sputtering. Geometry optimizations and energy calculations were performed on graphene-like model systems containing sulfur and fluorine atoms. It is shown that [S+F] concentrations in the range of 0−10 at.%, structural ordered characteristics similar to graphene pieces containing ring defects are energetically feasible. The modeling predicts that CSxFy thin films with graphite and fullerene-like characteristics may be obtained for the mentioned concentration range. Accordingly, thin films were synthesized from a graphite solid target and sulfur hexafluoride as reactive gas. In agreement with the theoretical prediction, transmission electron microscopy characterization and selected area electron diffraction confirmed the presence of small ordered clusters with graphitic features in a sample containing 0.4 at.% of S and 3.4 at.% of F.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-121470 (URN)10.1021/acs.jpcc.6b02718 (DOI)000375631100060 ()
Note

funding agencies: Swedish Foundation for Strategic Research (SSF) [RMA11-0029]; Carl Trygger Foundation for Scientific Research; Swedish Research Council [642-2013-8020]; ERC [258509]; Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials at Linkoping University 

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Available from: 2015-09-21 Created: 2015-09-21 Last updated: 2017-12-04Bibliographically approved

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