uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Understanding the effects of sputter damage in W–S thin films by HAXPES
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
Show others and affiliations
2014 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 305, 203-213 p.Article in journal (Refereed) Published
Abstract [en]

WS2 is an excellent solid lubricant in dry conditions, and can be applied as thin films. The analysis of WS2 and WS2-based films by x-ray photoelectron spectroscopy (XPS) can be challenging, due to contaminationand oxidized material on the surface. The investigations have traditionally therefore included sputter etching by ion bombardment, which however leads to changes of the remaining material. In this study, hard x-ray photoelectron spectroscopy (HAXPES) has been used to study W–S films deposited bymagnetron sputtering. High-resolution reference measurements for crystalline WS2 and metallic W are also presented. The W–S films were analyzed before and after sputter cleaning by Ar+ ion bombardment, using photon energies of 3 and 6 keV. The as-deposited films were found to consist mainly of a WSx phase,similar to WS2 but with a broader range of chemical states. It is shown that ion bombardment of the surface not only removes the outermost oxidized material, but also leads to preferential sputtering of sulfur and the formation of metallic tungsten. The results are of strong interest for the analysis of WS2-based materials, as they demonstrate that spectra from sputter-cleaned films include effects of sputter damage,and may not be representative of the original sample.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 305, 203-213 p.
National Category
Inorganic Chemistry Materials Chemistry Condensed Matter Physics
Research subject
Chemistry with specialization in Inorganic Chemistry; Physics with spec. in Atomic, Molecular and Condensed Matter Physics
URN: urn:nbn:se:uu:diva-224513DOI: 10.1016/j.apsusc.2014.03.038ISI: 000336525400028OAI: oai:DiVA.org:uu-224513DiVA: diva2:716971
Swedish Foundation for Strategic Research
Available from: 2014-05-13 Created: 2014-05-13 Last updated: 2014-10-22Bibliographically approved
In thesis
1. Triboactive Low-Friction Coatings Based on Sulfides and Carbides
Open this publication in new window or tab >>Triboactive Low-Friction Coatings Based on Sulfides and Carbides
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For sustainable development, it is highly important to limit the loss of energy and materials in machines used for transportation, manufacturing, and other purposes. Large improvements can be achieved by reducing friction and wear in machine elements, for example by the application of coatings. This work is focused on triboactive coatings, for which the outermost layer changes in tribological contacts to form so-called tribofilms. The coatings are deposited by magnetron sputtering (a physical vapor deposition method) and thoroughly chemically and structurally characterized, often theoretically modelled, and tribologically evaluated, to study the connection between the composition, structure and tribological performance of the coatings.

Tungsten disulfide, WS2, is a layered material with the possibility of ultra-low friction. This work presents a number of nanocomposite or amorphous coatings based on WS2, which combine the low friction with improved mechanical properties. Addition of N can give amorphous coatings consisting of a network of W, S and N with N2 molecules in nanometer-sized pockets, or lead to the formation of a metastable cubic tungsten nitride. Co-deposition with C can also give amorphous coatings, or nanocomposites with WSx grains in an amorphous C-based matrix. Further increase in coating hardness is achieved by adding both C and Ti, forming titanium carbide. All the WS2-based materials can provide very low friction (down to µ<0.02) by the formation of WS2 tribofilms, but the performance is dependent on the atmosphere as O2 and H2O can be detrimental to the tribofilm functionality.

Another possibility is to form low-friction tribofilms by tribochemical reactions between the two surfaces in contact. Addition of S to TiC/a-C nanocomposite coatings leads to the formation of a metastable S-doped carbide phase, TiCxSy, from which S can be released. This enables the formation of low-friction WS2 tribofilms when a Ti-C-S coating is run against a W counter-surface. Reduced friction, at a moderate level, also occurs for steel counter-surfaces, likely due to formation of beneficial iron sulfide tribofilms.

The studied coatings, whether based on WS2 or TiC, are thus triboactive, with the ability to form low-friction tribofilms in a sliding contact.



Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 86 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1183
coatings, thin films, tribology, tungsten disulfide, transition metal dichalcogenide, nanocomposite, TiC/a-C, tribofilms, PVD, XPS, HAXPES, XRD, SEM, TEM, Raman spectroscopy, nanoindentation
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
urn:nbn:se:uu:diva-230989 (URN)978-91-554-9041-6 (ISBN)
Public defence
2014-10-31, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Available from: 2014-10-09 Created: 2014-09-02 Last updated: 2015-01-23Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full texthttp://dx.doi.org/10.1016/j.apsusc.2014.03.038

Search in DiVA

By author/editor
Sundberg, JillLindblad, RebeckaRensmo, HåkanJansson, UlfLindblad, Andreas
By organisation
Inorganic ChemistryMolecular and condensed matter physics
In the same journal
Applied Surface Science
Inorganic ChemistryMaterials ChemistryCondensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 594 hits
ReferencesLink to record
Permanent link

Direct link