<p>Nickel based coatings were deposited on copper substrates by two different sputtering techniques from a nickel alloy based target. The substrates used were commercially available copper based substrates for low duty electrical contacts. The coatings were analyzed and evaluated as copper diffusion barriers for electrical contact applications. In addition two types of commercially available electroplated nickel coatings (referred to as type A electroplated coatings and type B electroplated coatings) were characterized for comparison. The Technique I sputtered coatings were deposited using three different substrate bias voltages and two different working gas pressures. The Technique II coatings were deposited using two different substrate bias voltages and two different working gas pressures. All sputtered coatings were deposited at a temperature of 200° C. The quality of the barriers was investigated by analyzing their composition, microstructure, stress, mechanical properties , and surface roughness. The results show that sputtered coatings have polycrystalline structures while the two plated films had (200) orientation and (111) orientation. Both plated coatings contained impurities that originate from chemicals used in the plating baths. The surface of the sputtered coatings reflects the substrate surface, while the electroplated samples on the same substrate (type A coatings) show a smooth mirror like surface and the type B electroplated coatings show a rough surface.</p><p>Technique II sputtered coatings showed the highest hardness in the amount of 13 GPa, followed by electroplated type A coatings with a hardness of about 9 GPa while the Technique I coatings showed hardness of 6-8 GPa. All sputtered coatings exhibited compressive stress while the electroplated type A coatings exhibited tensile stress of almost twice the magnitude.</p><p>In this study it is shown that sputtered nickel based coatings sputtered nickel based coatings are a promising more environmental friendly alternative to electroplated nickel coatings.</p>

<p>A microphone has been used to measure the dynamic pressure inside a vacuum chamber during high power impulse magnetron sputtering with high enough time-resolution (~µs) to track the pressure change during the discharge pulse. An experimental measurement of the dynamic pressure is of interest since it would give information about gas depletion, which is believed to dramatically alter the plasma discharge characteristics. This investigation has shown that the magnitude of the pressure wave, which arises due to the gas depletion, corresponds to a 0.4 - 0.7Pa (3 - 5.5mTorr) pressure difference at a distance of 15cm from the target, with base pressures of 2 - 6mTorr for a peak current of 110A. It has also been shown that another pressure wave, about 250µs later, can be detected. Its explanation is suggested to be that the initial pressure wave is bouncing against the chamber walls and thereby causing another peak.</p>

<p>Alumina-Zirconia thin films were grown on a range of substrates using dual magnetron sputtering. Film growth was achieved at a relatively low temperature of 450 °C and at higher temperatures up to 810 °C. The films were grown on well-defined surfaces such as silicon (100) but also on industrially relevant substrates such as hardmetal (WC-Co). Radio frequency power supplies were used in combination with magnetron sputtering to avoid problems with target arcing. A range of film compositions were possible by varying the power on each target. The influence of sputtering target were investigated, both ceramic oxide targets and metallic targets being used.</p><p>The phase composition of the as-deposited films was investigated by x-ray diffraction. The pure zirconia films contained the monoclinic zirconia phase, while the pure alumina films appeared either amorphous or contained the gamma-alumina phase. The composite films contained a mixture of amorphous alumina, gamma-alumina and the cubic zirconia phase. In-depth high-resolution electron microscopy studies revealed that the microstructures consisted of phase-separated alumina and zirconia nanocrystals in the case of the nanocomposites. In-situ spectroscopy was also performed to characterise the nature of the bonding within the as-deposited films.</p><p>The oxygen stoichiometry in the films was investigated as a possible reason for the stabilisation of the cubic zirconia phase in the nanocomposite. Ion beam techniques such as Rutherford backscattering scattering and electron recoil detection analysis were used in these studies. The growth of films with ceramic targets led to films that may be slightly understoichiometric in oxygen, causing the phase stabilisation. The growth of films from metallic targets necessitates oxygen rich plasmas and it is not expected that such films will be oxygen deficient.</p><p>Initial attempts were also made to characterise the mechanical properties of the new material with nanoindentation. The nanocomposite appeared to have greater resistance to wear than the pure zirconia film. In doing so, some surface interactions and some material interactions have been studied.</p> / Report code: LIU-TEK-LIC-2006:41

<p>The aim of this thesis was to develop wear resistant physical vapour deposited coatings of TiB₂ as well as multilayers of Cr/CrN. The correlation between deposition parameters and fundamental coating properties such as microstructure, composition, residual stress and hardness has been investigated. Finally, the influence of these properties on the coating behaviour in tribological applications has been evaluated.</p><p>It is shown that the use of electron bombardment of the growing coating during d.c. magnetron sputtering is beneficial for the growth of superhard TiB₂ coatings. Furthermore, electron bombardment results in TiB₂ coatings with significantly lower residual stresses than coatings deposited using ion bombardment. The low stresses in these coatings open up the possibility to deposit thicker PVD coatings, as confirmed in this thesis.</p><p>In addition, the use of TiB₂ coatings in tribological contacts against aluminium proved to be superior to many other commercial coatings used today, with respect to wear resistance, anti galling properties and a low friction.</p><p>Finally, a model is proposed which explains the observation that the abrasive wear resistance of multilayered Cr/CrN coatings can outperform that of the individual constituents. The model was found to satisfactory predict experimental data.</p>

<p>Spectrally selective solar absorber using composite Ni-NiO as coating materials was studied. Samples were prepared by dc magnetron sputtering unit named <i>Rulle</i>, which is a miniature copy of an industrial roll-coater unit. Using asymmetric location of the oxygen nozzele, it is possible to form the desired metallic concentration distribution along the sputtering zone under optimized conditions. This distribution can be transferred into a graded film profile by moving the substrate, obtaining good spectral selectivity. For specified mechanical settings (such as locations of gas sprays, target and pump positions etc.), the ratio of used oxygen flow to the corresponding critical oxygen flow, <b>RO</b>, is a dimensionless parameter to control the zone specification. The optimal value is around 0.80 for the <i>Rulle</i>. Optimized zone shows properties with two main parts: the metallic composite part of varied nickel volume fraction and the dielectric part. Two parts of the sputtering zone can form a graded absorbing layer with the right ratio of base and middle layer by the moving substrate technique. Distribution of normalized conductivity, <i>NC</i>, along the absorbing sputtering zone is a simple and good specification of zone property. Profile of graded film prepared by the moving substrate technique can be tailored according to <i>NC</i> distribution. XRD and XPS study confirms the <i>NC</i> results. Simulation reveals that absorption should mainly rely on the intrinsic, but less on the interference mechanism. Used metallic volume fraction of Ni-NiO is 0.3 for main absorbing layer. The front surface reflection loss due to high refractive index can be reduced by adding a layer with low refractive index on the top. Simulation shows that three-layer coatings are a good and simple coating structure. High solar absorptance of 0.97 has been achieved with low thermal emittance of 0.05 by theoretical simulation as well as experimentally prepared samples.</p>

Le but de ce travail est d’étudier l’effet de la vapeur d’eau contenue dans le plasma sur la composition et la vitesse de dépôt des couches minces d’oxynitrures de chrome déposées par pulvérisation cathodique magnétron réactive avec l’air contenant différentes teneurs en vapeur d’eau (humidité relative). Les techniques d’analyses par faisceau d’ions énergétiques : RBS et réactions nucléaires nous ont permis de déterminer les concentrations relatives des éléments déposés. Les profils d’hydrogène et d’azote ont été déterminés par RNRA et Tof- SIMS. La liaison chimique a été identifiée par LEEIXS et XPS. Les mesures XPS ont dévoilé la présence d’une phase autre que Cr, CrN, Cr2O3 et CrO2 ; cette nouvelle phase possède une stoechiométrie (CrO2)3-N. La teneur en Cr et ses composés varie en fonction du flux et de l’humidité relative de l’air. En mode métallique de la pulvérisation cathodique, la stoechiométrie Cr2O3 est majoritaire en coexistence avec de faibles teneurs et CrN, CrO2 et (CrO2)3-N alors qu’en mode composé, c’est la stoechiométrie CrO2 qui prédomine./ The aim of this work is to study the stoichiometry of chromium oxynitride thin films deposited by reactive magnetron sputtering in presence of air with various relative humidities. Ion Beam Analysis methods: RBS (Rutherford Backscattering Spectroscopy) and resonant nuclear reaction (RNRA) were used to determine the thickness and the composition of the films. Hydrogen and nitrogen profiles were obtained by RNRA and Tof-SIMS. The chemical bonds were investigated by XPS and LEEIXS. The chromium metallic and chromium compounds concentrations were measured versus the flow and relative humidity of the air. During sputtering in metallic mode, Cr2O3 stoichiometry is observed with low contents of CrN, CrO2 and (CrO2)3-N whereas in compound mode the CrO2 stoichiometry predominates.

In this work the roughness and topography evolution of optical materials sputtered with low energy ion beam (≤1 keV) has been investigated. These materials (bulk or thin layer) are used in the manufacturing of mirrors for scientific (ground or space) instruments or for other optical applications. In the first part of the work, the roughness evolution of optical surfaces under sputtering has been investigated in the frame of the industrial process known as Ion Beam Figuring. This technique consists in removing shape errors on optical surfaces with a low energy ion beam (≤1 keV). One disadvantage of this process is a potential increase of roughness for surfaces under treatment. The roughness evolution of some materials relevant to the optical industry has been accurately characterized as function of etching depth down to 5 µm. These sputtering experiments have been carried out at normal incidence, mainly with argon ions (but also in a lesser extent with krypton and xenon ions), ion current density of ~1 mA/cm2 and ion beam energy ranging from 200 eV to 1000 eV. The roughness evolution under sputtering is low for materials with amorphous (glass, electroless nickel), monocrystalline (silicon) or even polycrystalline structure (CVD silicon carbide, PVD gold or nickel film), whereas it is considerably more important for some other metallic materials such as electroplated nickel and aluminium. This work has shown small differences in the roughness evolution of CVD silicon carbide as function of the ion beam energy. The roughness increase is faster at low ion energy (<500 eV) than at higher ion energy (650-1000 eV). The grain structure of this material is less revealed at higher energy, which is supposed to be due to a larger amorphization of the sputtered layer in this case. The influence of the ion mass on CVD silicon carbide and gold films on nickel substrates has been also illustrated. Our measurements have been also compared to scaling laws. Various growth and roughness exponents have been found, sometimes rather different from those foreseen by the KPZ equation. In the second part, we focus on periodically modulated structures (ripples) which developed on many solids when sputtered by an off-normal ion bombardment. In this work, we first observed these ripples on gold films deposited on electroplated nickel (materials used as reflective surfaces for X-ray space telescope) sputtered at grazing incidence. We studied the influence of sputtering parameters (ion beam incidence angle, energy and flux) on the characteristics of ripples induced on gold and silver thin film (~0.2 µm). Ion-induced ripples have also been observed on CdS, an interesting semiconductor crystal for optical applications. The ripples orientation and dimensions (spatial wavelengths from 0.13 µm to 0.29 µm) have been confronted to the Bradley-Harper (B-H) linear model. We used the SRIM software to evaluate the deposited energy and the surface tension coefficient distributions. Our results can be in great part explained by the current theories (Bradley-Harper, Makeev) on morphology of ion-sputtered surfaces. These results can be summarized hereunder: Clear development of ripples for angle of incidence equal or higher than 60° on gold film and 70° on silver film. In this work the ripples wave vector is always perpendicular to the ion beam direction for all angles, whereas the change in ripple orientation beyond a critical angle is usually reported in literature. This is a due to the different shape of the energy distribution function for our sputtering conditions. Different regimes for roughness and topography evolution (grains, ripples) have been observed in function of the angle of incidence. 3 different areas can be distinguished, as predicted by Makeev non-linear model. The diminution of ripple wavelength with ion energy shows that thermal diffusion is the main relaxation mechanism.

Alumina-Zirconia thin films were grown on a range of substrates using dual magnetron sputtering. Film growth was achieved at a relatively low temperature of 450 °C and at higher temperatures up to 810 °C. The films were grown on well-defined surfaces such as silicon (100) but also on industrially relevant substrates such as hardmetal (WC-Co). Radio frequency power supplies were used in combination with magnetron sputtering to avoid problems with target arcing. A range of film compositions were possible by varying the power on each target. The influence of sputtering target were investigated, both ceramic oxide targets and metallic targets being used. The phase composition of the as-deposited films was investigated by x-ray diffraction. The pure zirconia films contained the monoclinic zirconia phase, while the pure alumina films appeared either amorphous or contained the gamma-alumina phase. The composite films contained a mixture of amorphous alumina, gamma-alumina and the cubic zirconia phase. In-depth high-resolution electron microscopy studies revealed that the microstructures consisted of phase-separated alumina and zirconia nanocrystals in the case of the nanocomposites. In-situ spectroscopy was also performed to characterise the nature of the bonding within the as-deposited films. The oxygen stoichiometry in the films was investigated as a possible reason for the stabilisation of the cubic zirconia phase in the nanocomposite. Ion beam techniques such as Rutherford backscattering scattering and electron recoil detection analysis were used in these studies. The growth of films with ceramic targets led to films that may be slightly understoichiometric in oxygen, causing the phase stabilisation. The growth of films from metallic targets necessitates oxygen rich plasmas and it is not expected that such films will be oxygen deficient. Initial attempts were also made to characterise the mechanical properties of the new material with nanoindentation. The nanocomposite appeared to have greater resistance to wear than the pure zirconia film. In doing so, some surface interactions and some material interactions have been studied. / Report code: LIU-TEK-LIC-2006:41

The aim of this thesis was to develop wear resistant physical vapour deposited coatings of TiB2 as well as multilayers of Cr/CrN. The correlation between deposition parameters and fundamental coating properties such as microstructure, composition, residual stress and hardness has been investigated. Finally, the influence of these properties on the coating behaviour in tribological applications has been evaluated. It is shown that the use of electron bombardment of the growing coating during d.c. magnetron sputtering is beneficial for the growth of superhard TiB2 coatings. Furthermore, electron bombardment results in TiB2 coatings with significantly lower residual stresses than coatings deposited using ion bombardment. The low stresses in these coatings open up the possibility to deposit thicker PVD coatings, as confirmed in this thesis. In addition, the use of TiB2 coatings in tribological contacts against aluminium proved to be superior to many other commercial coatings used today, with respect to wear resistance, anti galling properties and a low friction. Finally, a model is proposed which explains the observation that the abrasive wear resistance of multilayered Cr/CrN coatings can outperform that of the individual constituents. The model was found to satisfactory predict experimental data.

Spectrally selective solar absorber using composite Ni-NiO as coating materials was studied. Samples were prepared by dc magnetron sputtering unit named Rulle, which is a miniature copy of an industrial roll-coater unit. Using asymmetric location of the oxygen nozzele, it is possible to form the desired metallic concentration distribution along the sputtering zone under optimized conditions. This distribution can be transferred into a graded film profile by moving the substrate, obtaining good spectral selectivity. For specified mechanical settings (such as locations of gas sprays, target and pump positions etc.), the ratio of used oxygen flow to the corresponding critical oxygen flow, <b>RO</b>, is a dimensionless parameter to control the zone specification. The optimal value is around 0.80 for the Rulle. Optimized zone shows properties with two main parts: the metallic composite part of varied nickel volume fraction and the dielectric part. Two parts of the sputtering zone can form a graded absorbing layer with the right ratio of base and middle layer by the moving substrate technique. Distribution of normalized conductivity, NC, along the absorbing sputtering zone is a simple and good specification of zone property. Profile of graded film prepared by the moving substrate technique can be tailored according to NC distribution. XRD and XPS study confirms the NC results. Simulation reveals that absorption should mainly rely on the intrinsic, but less on the interference mechanism. Used metallic volume fraction of Ni-NiO is 0.3 for main absorbing layer. The front surface reflection loss due to high refractive index can be reduced by adding a layer with low refractive index on the top. Simulation shows that three-layer coatings are a good and simple coating structure. High solar absorptance of 0.97 has been achieved with low thermal emittance of 0.05 by theoretical simulation as well as experimentally prepared samples.