Transmission electron microscopy and energy dispersive X-ray spectroscopy on the worn surface of nano-structured TiAlN/VN multilayer coating

Nano-structured TiAIN/VN multilayer hard coatings grown by cathodic arc metal ion etching and unbalanced magnetron sputtering deposition have repeatedly shown low coefficients of friction and wear. In this paper, we employed the combined methods of cross-sectional ion beam milling sample preparation, conventional transmission electron microscopy, energy dispersive X-ray spectroscopy and quantitative spectrum analysis to give a comprehensive characterization of wear induced tribofilm, worn TiAIN/VN surface as well as wear debris. The major wear mechanism operating in the TiAIN/VN coating is the tribo-oxidation wear. A 20-50 nm thick tribofilm was observed on the TiAIN/VN worn surface, having inhomogeneous density, amorphous structure and multicomponent V-Al-Ti-O composition. Therefore the real sliding contact during the ball-on-disk test was a three-body sliding system including the tribofilm, in which the self-sintering and shearing deformation of the multicomponent oxide film played a significant role in determining the low friction coefficient. Owing to the low friction and high hardness, the TiAIN/VN worn surface retained good structural integrity without any crack, delamination or detectable deformation, resulting in minimized mechanical wear. (c) 2005 Elsevier B.V. All rights reserved

Novel techniques for the control of the properties of reactively-sputtered thin films

Precise control techniques are of fundamental importance in the accurate deposition of optical, mechanical, electrical and magnetic thin films. The objective of this work was twofold: to devise and evaluate novel control systems for reactive sputtering primarily oxide films, and investigate the effects of these processes on resultant film properties. [Continues.

Control of the properties of semiconducting thin films deposited using magnetron sputtering

The objective of the work was to deposit semiconducting thin films with controlled properties using unbalanced reactive magnetron sputtering. It was decided to utilise this technique because it offers high deposition rate and controllable in-situ ion bombardment of the growing film, desirable attributes from both research and production perspectives. Sputtering from a metal cathode in a reactive gas atmosphere introduces process instabilities which can result in a low degree of control over the stoichiometry, optical, electrical and structural properties of the films. Whilst the focus of the study was to achieve repeatable control over semiconducting film properties, additional areas of interest associated with the reactive sputtering process were investigated as the project developed. Improvements in magnetron design have been made to remove iron contamination from the extended poles, at the same time improving cathode utilisation. A new technique of bonding polycrystalline silicon cathodes to cooling shims has been developed using a sputtered threemetal multilayer process. DC sputtering of silicon in the presence of oxygen, nitrogen, nitrogen and oxygen, and nitrogen and air has been used to produce films of refractive index between 2.27 and 1.45 at rates between 0.5 and 2 nms-1 depending on composition. Refractive index and optical transmittance of the films have been closely controlled by varying gas flow and composition, and substitution of air for oxygen increased the sensitivity so that indices of oxy-nitride films could be tailored to one decimal place. The deposition of Indium-tin-oxide (ITO) onto glass substrates has been investigated, using a feedback control loop to control the otherwise unstable process...cont'

In-situ X-ray diffraction studies during growth of Ni-Ti shape memory alloy films and their complementary ex-situ characterization

Shape Memory Alloy (SMA) Ni-Ti films have attracted much interest as functional and smart materials due to their unique properties. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. Thus, the main challenge is not only the control of the microstructure, including stoichiometry and precipitates, but also the identification and control of the preferential orientation since it is a crucial factor in determining the shape memory behaviour. The aim of this PhD thesis is to study the optimisation of the deposition conditions of films of Ni-Ti in order to obtain the material fully crystallized at the end of the deposition, and to establish a clear relationship between the substrates and texture development. In order to achieve this objective, a two-magnetron sputter deposition chamber has been used allowing to heat and to apply a bias voltage to the substrate. It can be mounted into the six-circle diffractometer of the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility (ESRF), Grenoble, France, enabling an in-situ characterization by X-ray diffraction(XRD) of the films during their growth and annealing. The in-situ studies enable us to identify the different steps of the structural evolution during deposition with a set of parameters as well as to evaluate the effect of changing parameters on the structural characteristics of the deposited film. Besides the in-situ studies, other complementary ex-situ characterization techniques such as XRD at a laboratory source, Rutherford backscattering spectroscopy(RBS), Auger electron spectroscopy (AES), cross-sectional transmission electron microscopy (X-TEM), scanning electron microscopy (SEM), and electrical resistivity (ER) measurements during temperature cycling have been used for a fine structural characterization. In this study, mainly naturally and thermally oxidized Si(100) substrates, TiN buffer layers with different thicknesses (i.e. the TiN topmost layer crystallographic orientation is thickness dependent) and MgO(100) single crystals were used as substrates. The chosen experimental procedure led to a controlled composition and preferential orientation of the films. The type of substrate plays an important role for the texture of the sputtered Ni-Ti films and according to the ER results, the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation characteristics

Improved adhesion and tribological properties of altin-tisin coatings deposited by dcms and hipims on nitrided tool steels

Hard coatings, such as AlTiN-TiSiN, deposited by Physical Vapor Deposition (PVD) techniques are widely used in industrial applications to protect and increase the lifetime of industrial components, such as cutting tools, dies, and forming tools. Despite their great properties, such as high hardness and wear and oxidation resistance, they are limited in cases of severe conditions due to the poor adhesion between the coating and the substrate. Duplex treatments have commonly been used to improve the adhesive properties of PVD coatings, especially those of the cathodic arc evaporation type. The purpose of this study is to achieve coatings with the good properties of the Magnetron Sputtering processes but with higher adhesion than that achieved with these techniques, thus achieving coatings that can be used under the most severe conditions. In this work, an AlTiN-TiSiN coating was deposited by a combination of DC Magnetron Sputtering (DCMS) and High-Power Impulse Magnetron Sputtering (HiPIMS) after a gas nitriding pretreatment on 1.2379 and Vanadis 4 tool steels. Mechanical (ultra-microhardness and scratch tests) and tribological tests were carried out to study the improvement in the properties of the coating. Duplex-treated samples showed improved adhesion between the coating and the substrate, with second critical load (Lc2) values greater than 100 N. Furthermore, they showed great toughness and wear resistance. These results show that this type of coating technique could be used in the most extreme applications and that they can compete with other techniques and coatings that to date they have not been able to compete with.This research was funded in part by the Spanish Ministry of Science, Innovation and Universities through grants PGC2018-096855-B-C43 and PGC2018-096855-A-C44

The production and properties of TCO coatings prepared by pulsed magnetron sputtering from powder targets

Mith their unique transparent and conductive properties, TCO (transparent conductive oxide) coatings are becoming increasingly studied These commercially important coatings have a promising future due to their various applications as components in optoelectronic devices, photovoltaic solar cells, flat panel displays, electroluminescent devices, etc. Their high transmittance and low resistivity are generally achieved through the use of specific dopant materials, whilst adjustments are made to the deposition processes to improve the structure of the coatings. TCO coatings are commonly deposited by the magnetron sputtering process. Sputtering normally takes place from a solid plate, known as the target, of the material to be deposited. Clearly, each solid target can only be of a single composition. Thus, to change the compositions ofthe coatings, the whole target has to be replaced Furthermore, alloy, or doped targets can be very expensive and the choice ofavailable compositions is likely to be limited. In this project, instead of using solid targets, metal or ceramic powder blends were used as the targets. The powder blends were spread across the surface of a magnetron and lightly tamped down to produce a smooth surface. The benefits of this approach are that any material that is available in powderform can be considered as a target material and alloy or multi-component compositions can be readily blended The basic aim of this project, therefore, was to produce novel TCO coatings by magnetron sputteringfrom powder targets. The coatings were deposited in a specially designed rig with a number of important features, including a pulsed DC power supply and a closed magnetic field. The project concentrated on the production of commercially useful zinc oxide-based TCO coatings. Coatings were produced with different dopant materials and concentrations, and their optical and electrical properties were measured. After the coatings were annealed at 500 *Cfor 2 hours in vacuo, aluminum and gallium doped zinc oxide coatings showed their low resistivity, which were no larger than 5.19xI0-3S2cm, and the lowest resistivity was obtained from 3at% A 1-doped ZnO coating; 1.95 xI 00cm. The average transmittance in the visible range of the ZnO coatings was 90%. From this, optimal compositions were identified For comparison purposes, coatings were also produced of the TCO material most commonly used at present; namely ITO (Indium tin oxide). The results showed that ITO coatings generally had lower resistivity and visible transmittance, (4-6xlO-492cm and 80-8216), than doped ZnO coatings. Also, the electrical and optical properties of ITO coatings were very sensitive to the content of oxygen in the deposition atmosphere. Finally, theflexibility offered by this approach was exploited through the use of multi-component target compositions to produce TCO coatings with tailored optical and electrical properties.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Growth and characterization of an all solid-state high voltage Li-ion thin film battery.

238 p.All solid-state Li-ion batteries present key technological advantages that position them as a promising alternative to State-of-the-Art liquid electrolyte-based batteries, namely a wider electrochemical stability window, low toxicity, and hindered Li dentrite formation. These directly impact on the energy density, environmentally friendliness and safety, respectively. Importantly, all solid-state configurations also allow downscaling the whole battery to micrometric thin film components, paving the way towards the fabrication of compact microbatteries for low power energy supply. In this thesis, an all solid-state high voltage Li-ion thin film battery comprised of LiNi0.5Mn1.5O4 cathode, a LiPON solid electrolyte, and a metallic lithium anode has been developed, supported on high-value stainless steel current collector substrates. Growing parameters, individual film properties and issues related to the internal solid-solid interfaces are deeply analyzed