Industrial Deposition System Research Articles

Stoichiometric Cr2AlC MAX phase coatings deposited by HPPMS from composite targets using industrial deposition technology

Compositionally-graded Cr2AlC coatings were deposited from composite targets with Al concentration gradients along the long-axis of the targets, ranging from 20.0 to 30.0 at.%, in an industrial plant. Stoichiometric Cr2AlC coatings deposited by HPPMS with a peak-power density of 217 W/cm2 and at substrate bias potential of −100 V require an Al concentration in the target of 30.0 at.% to compensate for the Al-loss induced by preferential re-sputtering and thermally induced desorption at these deposition conditions. The HPPMS deposition of a stoichiometric Cr2AlC coating at floating potential can be attained from a target segment containing 26.4 at.% of Al. Hence, during synthesis at 560 °C in an industrial deposition system with two-fold rotation significant deviations between target and coating composition were observed. It was demonstrated that these ion energy and power density induced reductions in Al concentration can be compensated for by utilizing Al-rich composite targets.

Microstructural, Corrosion Resistance, and Tribological Properties of Al2O3 Coatings Prepared by Atmospheric Plasma Spraying

An usual material, EN-GJL-250 cast iron, used for automotive braking systems, was covered with a ceramic material (105NS-1 aluminium oxide) using an industrial deposition system (Sulzer Metco). The main reason was to improve the corrosion and wear (friction) resistance properties of the cast-iron. Samples were prepared by mechanical grinding and sandblasting before the deposition. We applied two and four passes (around 12-15 µm by layer) each at 90° obtaining ceramic coatings of 30 respectively 60 µm. The surface of the samples (with ceramic coatings) was investigated using scanning electron microscopy (SEM), dispersive energy spectroscopy (EDS) and X-ray diffraction (XRD). Scratch and micro-hardness tests were performed using CETR-UMT-2 micro-tribometer equipment. The better corrosion resistance of the base material was obtained by applying the ceramic coating. The results present a better corrosion resistance and a higher coefficient of friction of the coated samples.

Contamination of Substrate-Coating Interface Caused by Ion Etching

In–situ cleaning of the substrate surface by ion etching is an integral part of all physical vapor deposition (PVD) processes. However, in industrial deposition systems, some side effects occur during the ion etching process that can cause re-contamination. For example, in a magnetron sputtering system with several sputter sources and with a substrate holder located centered between them, the ion etching causes the contamination of the unshielded target surfaces with the batching material. In the initial stage of deposition, this material is redeposited back on the substrate surface. The identification of the contamination layer at the substrate–coating interface is difficult because it contains both substrate and coating elements. To avoid this problem, we prepared a TiAlN double coating in two separate production batches on the same substrate. In such a double-layer TiAlN hard coating, the contamination layer, formed during the ion etching before the second deposition, is readily identifiable, and analysis of its chemical composition is easy. Contamination of the batching material was observed also on seed particles that caused the formation of nodular defects. We explain the origin of these particles and the mechanism of their transfer from the target surface to the substrate surface. By comparison of the same coating surface area after deposition of the first and second TiAlN layers, the changes in coating topography were analyzed. We also found that after the deposition of the second TiAlN coating, the surface roughness slightly decreased, which we explain by the planarization effect.

TiAlN tribological coatings prepared in industrial deposition system with different rotations

Efficiency and lifetime of manufacturing tools and mechanica l components may be successfully improved by application of thin ceramic coatings. When it comes to tools for machining of hard materials such as machining of hardened steel, TiAlN is one of the most usually applied coatings. This material is of high hardness, high oxidation resistance and high temperature stability. In this research, surface morphology, mechanical and tribological properties of TiAlN coatings prepared in industrial deposition unit were studied. Three different coatings were prepared by selecting different rotational types in a magnetron sputtering deposition chamber. Surface morphology was characterized by stylus profilometry and atomic force microscopy, mechanical properties by nanoindentation technique and Rockwell indentation test, while pin-on-plate test was used to study tribological behavior. It was found that coatings prepared by higher number of rotations are smoother, harder, and more resistant to cracking and wear. These differences are attributed to differences in coating microstructure which refines with increased number of rotations.

Corrosion Resistance of a Cast-Iron Material Coated With a Ceramic Layer Using Thermal Spray Method

Cast-iron 250 used for breake systems present many corrosion signs after a mean usage time based on the environment conditions they work. In order to improve them corrosion resistance we propose to cover the active part of the material using a ceramic material. The deposition process is an industrial deposition system based on thermal spraying that can cover high surfaces in low time. In this articol we analyze the influence of a ceramic layer (40-50 µm) on the corrosion resistance of FC250 cast iron. The results were analyzed using scanning electron microscopy (SEM), X-ray energy dispersive (EDS) and linear and cyclic potentiometry.

Oxidation processes in vanadium-based single-layer and nanolayer hard coatings

We studied the oxidation resistance of CrVN single-layer, CrN/(Cr,V)N nanolayer and CrN/(Cr,V)N/VN nanolayer hard coatings with respect to the Cr:V atomic ratio. All the coatings were deposited by DC magnetron sputtering in an industrial deposition system. Using different target configurations we were able to prepare a series of samples with various Cr:V ratios. The following target arrangements were used: a) two sources with triangle-like, segmental Cr/V targets for depositing a single-layer CrVN coating with different Cr:V atomic ratios; b) two triangle-like, segmental Cr/V targets and two chromium targets for depositing the nanolayer CrN/(Cr,V)N coating; and c) two triangle-like, segmental Cr/V targets, one chromium and one vanadium target for depositing the nanolayer CrN/(Cr,V)N/VN coating.The analysis of the oxidation mechanisms for all three types of coatings showed that the formation of a thin chromium oxide layer slows down the diffusion of vanadium towards the surface. However, at the locations where the growth defects were present the vanadium kept diffusing at high rates and formed V2O5 dendritic structures at the surface. Vanadium oxide is known to have good lubricating properties at elevated temperatures, thus (Cr,V)N-based hard coatings could potentially be useful for the protection of hot-forging tools operating at high temperatures.

Substrate rotation-induced chemical modulation in Ti-Al-O-N coatings synthesized by cathodic arc in an industrial deposition plant

Reactive cathodic arc evaporation of Ti-Al-O-N was carried out in an industrial deposition system with two-fold substrate rotation. The structural and compositional evolution of the coatings was st ...

Designing the color of AlTiN hard coating through interference effect

Hard coatings are commonly used in decorative applications due to their attractive colors and high wear resistance. In most cases only intrinsic colors of the coatings are exploited. Such colors are determined by the stoichiometry of the coating and can be varied only in a limited range. We demonstrate a more flexible concept of color design by utilizing the interference effect in semi-transparent and reflective materials. In this design a thin film of partially transparent hard coating material is deposited over a material with specific reflectivity. Such construction enables wider color control since the interference-based colors can be tuned by the thickness of the interference layer and by the optical constants of the thin film and the reflective substrate. In this work such principle is demonstrated with AlTiN. A single-layer of AlTiN was deposited by DC magnetron sputtering on substrates with different reflectivities. Colors of high saturation, ranging from yellow, pink, violet to blue, were prepared by varying the thickness of AlTiN in the range of 20–55nm. Optical properties were studied by spectrophotometry and ellipsometry. Only small color shifts were measured with the angle of observation. Interference-based color design is further demonstrated on the tools with complex geometry combining protective and decorative functionality of the coating. A uniform blue color was prepared in an industrial deposition system on drills of different sizes.

Influence of substrate rotation and target arrangement on the periodicity and uniformity of layered coatings

In physical vapor deposition, the material is vaporized from a target and deposited on the areas of substrate that are in the line-of-sight of a vaporization source. To ensure uniform deposition, substrates are positioned on a turntable and rotated in a manner similar to the planetary rotation. In industrial deposition systems the turntable rotates around several axes and moves substrates along different targets. The substrate rotation and the target arrangement therefore determine the uniformity of the deposited material. When different target materials are used coatings can be prepared in a layered structure; in such a case, the rotation and the target arrangement also determine the layer structure of the coatings. In the present paper a computer simulation of coating growth in an industrial deposition system with a planetary type of rotation has been used to analyze the influence of the rotation and the target arrangement on the uniformity and the periodicity of layered coatings. Results of simulations show that highly periodic modes of rotation, which are determined by the turntable gear ratio and the switch angle, cause large non-uniformities both in the thickness and the composition of layered coatings. On the other hand, less periodic modes of rotation produce better coating uniformity although for certain rotation parameters significant non-uniformities may also occur. Exact periodicity of layered coatings can be calculated from the least common multiple of revolution times around individual axes. Calculations of coating thickness and composition on the perimeter of a round tool show that the uniformity also depends on the deposition time. Configuration with maximally separated targets produces better coating uniformity than configuration with closely positioned targets.

ZrB2 thin films grown by high power impulse magnetron sputtering from a compound target

ZrB2 thin films were grown on Si by high power impulse magnetron sputtering (HiPIMS) from a compound target in an industrial deposition system. By keeping a constant average power while modifying the HiPIMS pulse repetition frequency, the pulse peak current and thereby the degree of ionisation was varied. The films were characterised using X-ray diffraction techniques, scanning electron microscopy, time-of-flight elastic recoil detection analysis, and four-point probe measurements. It was found that the composition of the films matched closely that of the target material, and the films were low in contamination. The films were crystalline with a strong (000n) preferred orientation, and that the residual stress could be adjusted, from tensile to compressive, by increasing the degree of ionisation. The film morphology appeared dense, with a smooth surface, and the resistivity was found to range from 180 to 250μΩcm with no clear dependence on frequency in the investigated parameter range.

B4C thin films for neutron detection

Due to the very limited availability of 3He, new kinds of neutron detectors, not based on 3He, are urgently needed. Here, we present a method to produce thin films of 10B4C, with maximized detection efficiency, intended to be part of a new generation of large area neutron detectors. B4C thin films have been deposited onto Al-blade and Si wafer substrates by dc magnetron sputtering from natB4C and 10B4C targets in an Ar discharge, using an industrial deposition system. The films were characterized with scanning electron microscopy, elastic recoil detection analysis, x-ray reflectivity, and neutron radiography. We show that the film-substrate adhesion and film purity are improved by increased substrate temperature and deposition rate. A deposition rate of 3.8 Å/s and substrate temperature of 400 °C result in films with a density close to bulk values and good adhesion to film thickness above 3 μm. Boron-10 contents of almost 80 at. % are obtained in 6.3 m2 of 1 μm thick 10B4C thin films coated on Al-blades. Initial neutron absorption measurements agree with Monte Carlo simulations and show that the layer thickness, number of layers, neutron wavelength, and amount of impurities are determining factors. The study also shows the importance of having uniform layer thicknesses over large areas, which for a full-scale detector could be in total ∼1000 m2 of two-side coated Al-blades with ∼1 μm thick 10B4C films.

Influence of ionization degree on film properties when using high power impulse magnetron sputtering

Chromium thin films are deposited by combining direct current magnetron sputtering and high power impulse magnetron sputtering (HiPIMS) on a single cathode in an industrial deposition system. While maintaining a constant deposition rate and unchanged metal ion energy distribution function, the fraction of the total power supplied by either deposition technique is altered, and thereby also the metal ion to metal neutral ratio of the deposition flux. It is observed that the required total average power needed to be proportionally increased as the HiPIMS fraction is increased to be able to keep a constant deposition rate. The influence on microstructure, electrical, and electrochemical properties of the films is investigated and shows improvements with the use of HiPIMS. However, considerable influence of the studied properties occurs already when only some 40% of the total power is supplied by the HiPIMS technique. Further increase of the HiPIMS power fraction results in comparatively minor influence of the studied properties yet significant deposition rate efficiency reduction. The results show that the degree of ionization can be controlled separately, and that the advantages associated with using HiPIMS can be obtained while much of the deposition rate reduction, often reported for HiPIMS, can be avoided.

Optimization of the mechanical properties of magnetron sputtered diamond-like carbon coatings

Diamond-like carbon coatings containing hydrogen, a-C:H, were deposited by use of reactive DC magnetron sputtering with an industrial deposition system. The reactive gas C 2H 2 was used in combination with carbon targets. Using Raman spectroscopy, nanoindentation and Rockwell C indentation, the mechanical properties of the coatings were optimized. Excessively high compressive stresses, which were measured with Raman spectroscopy, were found in the coatings with high hardness, resulting in poor adhesion to the substrates. By thermal annealing, these compressive stresses were reduced without altering the hardness, resulting in diamond-like carbon coatings with good adhesion.

Time and energy resolved ion mass spectroscopy studies of the ion flux during high power pulsed magnetron sputtering of Cr in Ar and Ar/N 2 atmospheres

Mass spectroscopy was used to analyze the energy and composition of the ion flux during high power pulsed magnetron sputtering (HIPIMS/HPPMS) of a Cr target in an industrial deposition system. The ion energy distribution functions were recorded in the time-averaged and time-resolved mode for Ar +, Ar 2+, Cr +, Cr 2+, N 2 + and N + ions. In the metallic mode the dependence on pulse energy (equivalent of peak target current) was studied. In the case of reactive sputtering in an Ar/N 2 atmosphere, variations in ion flux composition were investigated for varying N 2-to-Ar flow ratio at constant pressure and HIPIMS power settings. The number of doubly charged Cr ions is found to increase linearly with increasing pulse energy. An intense flux of energetic N + ions was observed during deposition in the reactive mode. The time evolution of ion flux composition is analyzed in detail and related to the film growth process. The ionization of working gas mixture is hampered during the most energetic phase of discharge by a high flux of sputter-ejected species entering the plasma, causing both gas rarefaction and quenching of the electron energy distribution function. It is suggested that the properties (composition and energy) of the ion flux incident on the substrate can be intentionally adjusted not only by varying the pulse energy (discharge peak current), but also by taking advantage of the observed time variations in the composition of ion flux.

Limiting factors in the fabrication of microcrystalline silicon solar cells and microcrystalline/amorphous (‘micromorph’) tandems

This contribution presents the status of amorphous and microcrystalline silicon solar cells on glass, and discusses some material/fabrication factors that presently limit their conversion efficiency. Particular attention is focused on recent results and developments at the Institute of Microtechnology (IMT) in Neuchâtel. The performances and stability of microcrystalline silicon single-junction and amorphous/microcrystalline (‘micromorph’) tandem solar cells are discussed, as a function of material properties. Recent results on the electrical effect of cracks in microcrystalline silicon material are presented. Degradation under the effect of illumination is a well-known limiting factor for amorphous silicon solar cells. As a comparison, studies on the stability of microcrystalline silicon with respect to light-induced degradation are commented upon. The importance of transparent contacts and anti-reflection layers for achieving low electrical and optical losses is discussed. Finally, efforts towards industrialization of micromorph tandem solar cells are highlighted, specifically (i) the development and implementation of an in situ intermediate reflector in a large-area industrial deposition system, and (ii) recent achievements in increasing the growth rate of microcrystalline silicon.