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Carbon Nitride and Carbon Fluoride Thin Films Prepared by HiPIMS
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis focuses on carbon based thin films prepared by high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS). Carbon nitride (CNx: 0 < x < 0.20) as well as carbon fluoride (CFx: 0.16 < x < 0.35) thin films were synthesized in an industrial deposition chamber by reactive magnetron sputtering of graphite in Ne/N2, Ar/N2, Kr/N2, Ar/CF4, and Ar/C4F8 ambients. In order to increase the understanding of the deposition processes of C in the corresponding reactive gas mixture plasmas, ion mass spectroscopy was carried out. A detailed evaluation of target current and target voltage waveforms was performed when graphite was sputtered in HiPIMS mode. First principle calculations targeting the growth of CFx thin films revealed most probable film forming species as well as CFx film structure defining defects. In order to set different process parameters into relation with thin film properties, the synthesized carbon based thin films were characterized with regards to their chemical composition, chemical bonding, and microstructure. A further aspect was the thin film characterization for possible applications. For this, mainly nanoindentation and contact angle measurements were performed. Theoretical calculations and the results from the characterization of the deposition processes were successfully related to the thin film properties.

The reactive graphite/N2/inert gas HiPIMS discharge yielded high ion energies as well as elevated C+ and N+ abundances. Under such conditions, amorphous CNx thin films with hardnesses of up to 40 GPa were deposited. Elastic, fullerene like CNx thin films, on the other hand, were deposited at increased substrate temperatures in HiPIMS discharges exhibiting moderate ion energies. Here, a pulse assisted chemical sputtering at the target and the substrate was found to support the formation of a fullerene-like microstructure.

CFx thin films were found to have surface energies equivalent to super-hydrophobic materials for x > 0.26 while such films were polymeric in nature accounting for hardnesses below 1 GPa. Whereas, an amorphous structure for carbon-based films with fluorine contents ranging between 16 % and 23 % was observed. For those films, the hardness increased with decreasing fluorine content and ranged between 16 GPa and 4 GPa. The HiPIMS process in fluorinecontaining atmosphere was found to be a powerful tool in order to change the surface properties of carbon based thin films.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. , 82 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1512
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-90912ISBN: 978-91-7519-642-8 (print)OAI: oai:DiVA.org:liu-90912DiVA: diva2:615039
Public defence
2013-05-08, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2013-04-08 Created: 2013-04-08 Last updated: 2016-08-31Bibliographically approved
List of papers
1. 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
2. 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
3. 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
4. Ion mass spectrometry investigations of the discharge during reactive high power pulsed and direct current magnetron sputtering of carbon in Ar and Ar/N-2
Open this publication in new window or tab >>Ion mass spectrometry investigations of the discharge during reactive high power pulsed and direct current magnetron sputtering of carbon in Ar and Ar/N-2
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2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 1, 013305- p.Article in journal (Refereed) Published
Abstract [en]

Ion mass spectrometry was used to investigate discharges formed during high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) of a graphite target in Ar and Ar/N-2 ambient. Ion energy distribution functions (IEDFs) were recorded in time-averaged and time-resolved mode for Ar+, C+, N-2(+), N+, and CxNy+ ions. An increase of N-2 in the sputter gas (keeping the deposition pressure, pulse width, pulse frequency, and pulse energy constant) results for the HiPIMS discharge in a significant increase in C+, N+, and CN+ ion energies. Ar+, N-2(+), and C2N+ ion energies, in turn, did not considerably vary with the changes in working gas composition. The HiPIMS process showed higher ion energies and fluxes, particularly for C+ ions, compared to DCMS. The time evolution of the plasma species was analyzed for HiPIMS and revealed the sequential arrival of working gas ions, ions ejected from the target, and later during the pulse-on time molecular ions, in particular CN+ and C2N+. The formation of fullerene-like structured CNx thin films for both modes of magnetron sputtering is explained by ion mass-spectrometry results and demonstrated by transmission electron microscopy as well as diffraction.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-80790 (URN)10.1063/1.4733692 (DOI)000306513400018 ()
Note

Funding Agencies|Hungarian Academy of Sciences||

Available from: 2012-08-30 Created: 2012-08-30 Last updated: 2017-12-07
5. Influence of inert gases on the reactive high power pulsed magnetron sputtering process of carbon-nitride thin films
Open this publication in new window or tab >>Influence of inert gases on the reactive high power pulsed magnetron sputtering process of carbon-nitride thin films
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2013 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 31, no 1, 011503- p.Article in journal (Refereed) Published
Abstract [en]

The influence of inert gases (Ne, Ar, Kr) on the sputter process of carbon and carbon-nitride (CNx) thin films was studied using reactive high power pulsed magnetron sputtering (HiPIMS). Thin solid films were synthesized in an industrial deposition chamber from a graphite target. The peak target current during HiPIMS processing was found to decrease with increasing inert gas mass. Time averaged and time resolved ion mass spectroscopy showed that the addition of nitrogen, as reactive gas, resulted in less energetic ion species for processes employing Ne, whereas the opposite was noticed when Ar or Kr were employed as inert gas. Processes in nonreactive ambient showed generally lower total ion fluxes for the three different inert gases. As soon as N-2 was introduced into the process, the deposition rates for Ne and Ar-containing processes increased significantly. The reactive Kr-process, in contrast, showed slightly lower deposition rates than the nonreactive. The resulting thin films were characterized regarding their bonding and microstructure by x-ray photoelectron spectroscopy and transmission electron microscopy. Reactively deposited CNx thin films in Ar and Kr ambient exhibited an ordering toward a fullerene-like structure, whereas carbon and CNx films deposited in Ne atmosphere were found to be amorphous. This is attributed to an elevated amount of highly energetic particles observed during ion mass spectrometry and indicated by high peak target currents in Ne-containing processes. These results are discussed with respect to the current understanding of the structural evolution of a-C and CNx thin films.

Place, publisher, year, edition, pages
American Vacuum Society, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-89755 (URN)10.1116/1.4769725 (DOI)000313931300007 ()
Note

Funding Agencies|ERC||Hungarian Academy of Sciences||

Available from: 2013-03-05 Created: 2013-03-05 Last updated: 2017-12-06
6. The Influence of Inert Gases on the a-C and CNx Thin Film Deposition: A Comparison between DCMS and HiPIMS Processes
Open this publication in new window or tab >>The Influence of Inert Gases on the a-C and CNx Thin Film Deposition: A Comparison between DCMS and HiPIMS Processes
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

DCMS and HiPIMS discharges of C in Ne, Ar, and Kr as well as their reactive counterparts (N2/Ne, N2/Ar, and N2/Kr) were investigated for the growth of carbon and carbon-nitride (CNx) thin films. The thin films were synthesized in an industrial deposition chamber from a pure graphite target. Time averaged plasma mass spectroscopy showed that the energies of the most abundant plasma cations depend on the inert gas and the amount of N2 in the sputter gas rather than the sputter modes. The ion species population in the plasma, on the other hand, was found to depend heavily on the sputter mode; HiPIMS processes yield approximately ten times higher flux ratios of ions originating from the target to ions originating from the process gas. Exceptional cases are the discharges in Ne or N2/Ne mixtures containing up to 20% N2. Here, no influence of the sputter mode on cation energies and population was found. CNx and a-C thin films deposited in 14% N2/inert gas mixture and pure inert gas, respectively, were characterized regarding the chemical composition, chemical bonding and microstructure as well as their mechanical properties using elastic recoil detection analysis, X-ray photoelectron spectroscopy, transmission electron microscopy in combination with selected area electron diffraction, and nanoindentation, respectively. The thin film characteristics showed strong correlations to the energies of abundant plasma cations (namely C+, Ar+, Ar++, Ne+,22Ne+, Ne++, 82Kr+, 84Kr+, 86Kr+, Kr++, N+, N2+, CN+ as well as C2N2+)and cation population of the corresponding deposition process. High amounts of C bond in sp3 hybridization state were found for thin films sputtered in Ne, accounting for their elevated hardness and amorphous microstructure. With increasing inert gas atomic number the a-C and CNx thin films show an increasingly distinct near range ordered microstructural evolution. This effect is more pronounced for HiPIMS processes and accompanied by a lowered hardness, but elevated elastic properties.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-90910 (URN)
Available from: 2013-04-08 Created: 2013-04-08 Last updated: 2016-08-31Bibliographically approved

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