Growth of WC-Cr-N and WC-Al-N coatings in a RF-magnetron sputtering process

Tungsten carbide-based coatings have been used in a wide variety of industrial applications such as high speed cutting tools, extrusion dies, drills, aerospace industries, and more. A few reports on ternary and quaternary coatings of WC with other elements indicate good prospects for these material systems. The present study focuses on the formation of quaternary WCeCreN and WCeAleN coatings during the simultaneous reactive RF-magnetron sputtering of tungsten carbide and Al or Cr targets in an argon/nitrogen gas mixture. The resulting coatings, with thicknesses of 3.5 mme8.2 mm, were characterized by using several analytical techniques including X-ray diffraction, SEM/EDS, AFM, and X-ray photoelectron spectroscopy. WCeCreN and WCeAleN coatings with high levels of tungsten (i.e. more than 50 at.% of the total metal content) demonstrated dense microstructure. Coatings with lower tungsten content formed columnar grain microstructure, with different surface morphologies depending on the process parameters. It was proposed that crystalline tungsten carbide (with partial N-substitution of C atoms) and chromium (or aluminum) nitride phases coexist in the coatings when the amount of tungsten was greater than 50 at.% of the total metal content; while at lower tungsten content, the dominating crystalline phase is either W-doped CrN1 y or AlN1 y solid solution, with WC1 x and small amounts of free sp2-bonded carbon present as X-ray amorphous phases.U.S. National Science Foundation under the awards DMR-0806521, DRM-0922910 Regional Council of Burgundy, Franc

Electron energy loss spectroscopy determination of Ti oxidation state at the (001) LaAlO3/SrTiO3 interface as a function of LaAlO3 growth conditions

At the (001) interface between the two band-insulators LaAlO3 and SrTiO3, a high-mobility electron gas may appear, which has been the object of numerous works over the last four years. Its origin is a subject of debate between the interface polarity and unintended doping. Here we use electron energy loss 'spectrum images', recorded in cross-section in a scanning transmission electron microscope, to analyse the Ti3+ ratio, characteristic of extra electrons. We find an interface concentration of Ti3+ that depends on growth conditions.Comment: 6 page

Curvature radius measurement by optical profiler and determination of the residual stress in thin films

The Stoney formula, based on the measurement of the substrate curvature, is often used for the determination of the thin films' residual stress. In this study, titanium nitride coatings were deposited by DC reactive magnetron sputtering on silicon substrates. An optical profiler was used to determine the curvature of the surface before and after coating. Two radii were then obtained, along the principal perpendicular directions of the surface curvature. A simple and efficient method to determine the experimental error on the stress calculation was developed taking into account the film thickness dispersion and the radii dispersion. Using constant deposition parameters, some samples' characteristics were tested: film and substrate thickness, size, shape and crystallographic orientations of the substrates. With the help of the developed error method, we analyzed what can be conclude about the influence of these characteristics on the calculated stress values, obtained from the experimental measurements

Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition

Many of today’s demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2–20 m and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.US National Science Foundation grants (DMR-08606521 and DMR-0922910) and the Regional Council of Burgundy, Franc

Structuration of nanometric tungsten/tungsten oxide periodic films combining gas pulsing and glancing angle deposition

POSTER - EMRS 2013 - 27-31 mai 2013Structuration of nanometric tungsten/tungsten oxide periodic films combining gas pulsing and glancing angle depositio

Chemical and structural characterization of periodic metal/oxide nanometric layers using STEM-EELS

POSTER - International Electron Energy Loss Spectroscopy Meeting - EDGE 2013, Saint-Maxime, 26 - 31 May 2013Chemical and structural characterization of periodic metal/oxide nanometric layers using STEM-EEL

Etude de systèmes ternaires à base de Cr et N pour applications mécaniques sur outils de coupe destinés à la transformation du bois

Les actes de ce colloque francophone ont été mis sur un CD-Rom, pas en version papier.Le présent travail se propose d'étudier les propriétés physico-chimiques et mécaniques de revêtements PVD nanocristallins ou nanocomposites (CrAlN, CrSiN) obtenus sur différents substrats et destinés à la première et seconde transformation du bois une fois leur optimisation effectuée. Pour cela, les couches de CrAlN obtenues par magnétron RF ont subit des observations au MEB afin de déterminer la morphologie des couches alors que de la microanalyse EDS a défini leur composition. La structure des couches a été déterminée par diffraction de rayons X. Nous avons alors mesuré l’épaisseur des couches par profilométrie et par interférométrie puis on en a déduit les contraintes internes de celles-ci. L’adhérence et la dureté des couches ont été obtenues par scratch-tests et nanoindentation. Enfin, des analyses plus fines telles que de l’XPS et du SIMS ont été réalisées afin de déterminer les phases en présence dans ces couches. La co-pulvérisation réactive des cibles de Cr et Si en position confocale, est un procedé séduisant pour l’élaboration de films de CrSiN avec une structure nanocomposite du type nc-CrN/a-SiNx. Les analyses EDS et les caractérisations par DRX et nanoindentation confirment dans ces films la présence de phase cristallisée de type CrN et la possibilité de faire varier leur teneur en silicium corrélée avec des changements de dureté.Conseil Régional de Bourgogne ainsi que le Conseil Régional de Franche-Comté dans le cadre de ce projet transrégional intitulé « ROBUS », CTBA cofinanceur de la thèse de C. Labid

Structural and electrical properties in tungsten/tungsten oxide multilayers

International audienceTungsten and tungsten oxide periodic nanometric multilayers have been deposited by DC reactive sputtering using the reactive gas pulsing process. Different pulsing periods have been used for each deposition to produce metal-oxide periodic alternations ranging from 3.3 to 71.5 nm. The morphology, crystallinity and chemical composition of these films have been investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy techniques. The produced multilayers exhibited an amorphous structure and the composition stability of WO3 sub-layers has been pointed out. Moreover, electrical properties have also been studied by the van der Pauw technique. It revealed a clear stability of resistivity versus temperature for almost all samples and an influence of the multilayered structure on the resistivity behavio

Architectured columns with a metal-dielectric periodic nanostructure

International audienceWe engineer a sputter deposited metal/oxide periodic structure based on W and Ta,and correspondingoxides with tuneable alternations from a few nanometers to a few tens nanometers,combined with thepreparation of inclined, zigzag and spiral columns. This work shows how bi-component periodic mul-tilayers can be produced within some inclined nano-columns exhibiting oriented, zigzag and helixstructures. This unique combination of controlled columnar structure and periodic multilayers enablesnew opportunities to create some unusual structural designs for functional materials

Influence of flash annealing on structure and electrical properties of multilayered TiO2/TiO/Ti thin films

POSTER - European Materials Research Symposium - EMRS2013, Strasbourg, 27 - 31 May 2013Influence of flash annealing on structure and electrical properties of multilayered TiO2/TiO/Ti thin film