Comparison of chromium nitride coatings deposited by DC and RF magnetron sputtering

Chromium nitride coatings were deposited by DC and RF reactive magnetron sputtering on AISI 304 stainless steels without substrate heating. A Cr₂N phase was formed in the RF sputtered coatings with a low N₂ flow content ranging within 30-50%. A NaCl type CrN_x phase was obtained by DC magnetron sputtering with different N₂ flow contents. The coating hardness increased with the increase of the N₂ flow content. When the coatings deposited with the same N₂ flow content were compared, the hardness of the RF sputtered CrN_x was higher than that of the DC sputtered CrN_x, which was mainly due to the distinct difference between the dense structure (RF process) and the porous structure (DC process). The RF sputtered CrN_x coatings showed an excellent adhesion strength as compared to the DC sputtered coatings. By selecting the deposition method and optimizing the N₂ flow content, CrN_x coatings with a preferred microstructure could be obtained, which would be a candidate material for research and applications in nano-science.     

Novel coatings for unique applications

In the present article three different coatings systems are discussed based on reactive and non-reactive sputtering processes utilizing HiPIMS, pulsed DC and DC magnetron sputtering. The HiPIMS platform was used to develop a very hard TiB₂ coating with a low residual stress level. Pulsed DC magnetron sputtering was used to deposit 50 μm thick amorphous Al₂O₃ coating. Finally DC magnetron sputtering was used to deposit a Sr-Ti-O coating capable of releasing Sr facilitating accelerated bone formation and implant ingrowth.     

Comparative analysis of Cr-B coatings deposited by magnetron sputtering in DC and HIPIMS modes

Surface coatings of the Cr-B system have been obtained by magnetron sputtering in the DC and high-power impulse (HIPIMS) regimes. It is established that the passage from the DC regime to HIPIMS leads to suppression of the columnar grain growth and a twofold increase in the resistance of coatings to plastic deformation, while the plasticity index and hardness of coatings increase by 29 and 18%, respectively.     

The Structure and Properties of Ti–B–N, Ti–Si–B–N, Ti–Si–C–N, and Ti–Al–C–N Coatings Deposited by Magnetron Sputtering Using Composite Targets Produced by Self-Propagating High-Temperature Synthesis (SHS)

The microstructures and compositions of multicomponent Ti–B–N, Ti–Si–B–N, Ti–Si–C–N, and Ti–Al–C–N films deposited by reactive magnetron sputtering using composite targets and produced by self-propagating high-temperature synthesis (SHS) have been investigated by means of transmission electron microscopy. Auger spectroscopy, and X-ray diffraction. Depending on the chemical composition of the film deposited, different single-phase crystalline films were observed. The sputtering process included sputter cleaning prior to the DC magnetron sputter deposition of Ti and TiN interlayers prior to DC magnetron sputter deposition of the multicomponent films from multicomponent targets. The films produced were characterized in terms of their microhardness, wear resistance, high-temperature oxidation conducted in air. and corrosion resistance in a solution of 5NH₂SO₄ at room temperature.     

Deposition of photocatalytic titania coatings on polymeric substrates by HiPIMS

Titania coatings have been deposited onto PET substrates by reactive magnetron sputtering in the HiPIMS (high power impulse magnetron sputtering) mode and for comparison, pulsed DC mode. In the latter case, the substrate showed evidence of melting, but the HiPIMS results were dependent on the characteristics of the power supply when operating under nominally identical conditions. A coating deposited by one of the HiPIMS supplies was found to have a mixed phase structure and to demonstrate a level of photocatalytic activity comparable to conventional coatings which had been post-deposition annealed.     

Magnetron sputtered NbN films with electroplated Cr interlayer

NbN films were deposited on SS substrates by reactive DC magnetron sputtering at various N₂ flow rates and substrate biasing. Coatings were studied for their thickness, structure, hardness and adhesion aspects. Process parameters were optimized for deposition of NbN coatings. NbN coatings were then extended on to MS substrates with Cr interlayer in three different thicknesses of 2, 4 and 10 μm. Cr was deposited by electroplating. The duplex coatings have been studied for the improvement with respect to surface hardness by Knoop micro indentation, adhesion by scratch testing and corrosion performance by potentiodynamic polarization technique. Open circuit potentials were also measured.     

Application of magnetron sputtering for producing bioactive ceramic coatings on implant materials

Radio frequency (RF) magnetron sputtering is a versatile deposition technique that can produce thin, uniform, dense calcium phosphate coatings. In this paper, principle and character of magnetron sputtering is introduced, and development of the hydroxyapatite and its composite coatings application is reviewed. In addition, influence of heat treatment on magnetron sputtered coatings is discussed. The heat treated coatings have been shown to exhibit bioactive behaviour both in vivo and in vitro. At last, the future application of the bioactive ceramic coating deposited by magnetron sputtering is mentioned.     

Annealing of sputter-deposited nanocrystalline Cr-Ta coatings in a low-oxygen-containing atmosphere

As a protective hard coating on glass molding dies, Cr-Ta coatings were fabricated on binderless tungsten carbide substrates with a Ti interlayer by RF magnetron sputtering. The nanocrystalline Cr-Ta coatings were deposited at 550 °C, which revealed one nanocrystalline phase for the Ta-rich coating and two nanocrystalline phases for the Cr-rich coating. Annealing treatment was conducted at 600 °C in a 12 ppm O₂-N₂ atmosphere to evaluate the coating performance in a realistic glass molding environment. Both Auger electron spectroscopy and X-ray photoelectron spectroscopy depth profiles verified the outward diffusion of Cr, which formed a protective coating for the Cr-rich coatings. A scale of Cr₂O₃ and a Cr-depleted transition zone near the surface were identified by conducting a transmission electron microscopy investigation on the annealed Cr_0.71Ta_0.29 coating. The Cr-rich coating absorbed a smaller amount of oxygen, exhibited greater hardness, and maintained nanoscale surface roughness after annealing in the glass molding atmosphere, thus making it an appropriate protective coating for the die material.     

Novel, nanoporous silica and titania layers fabricated by magnetron sputtering

Composite asymmetric membranes are fabricated through the deposition of submicrometer thick (100 nm) silica (SiO(2)) and titania (TiO(2)) films onto flat nanoporous silica and zirconia substrates by magnetron sputtering. The deposition conditions for both coating types were systematically altered to determine their influence on the deposited coating morphology and thickness. Ideal He/N(2) gas selectivity was measured for all of the membranes. The TiO(2) coatings, when deposited onto a ZrO(2) support layer with a pore size of 3 nm, formed a long columnar grain structure with average column diameter of 38 nm. A similar columnar structure was observed for TiO(2) coatings deposited onto a SiO(2) support layer with a pore size of 1 nm. Under the same conditions, SiO(2) coatings, deposited onto the same SiO(2) supports, formed a closely packed spherical grain structure whereas, when deposited onto ZrO(2) supports, the SiO(2) coatings formed an open grain structure. The average SiO(2) grain diameter was 36 nm in both cases. This preliminary investigation was aimed at studying the effect of sputtering parameters on the density and morphology of the deposited coatings. For the depositions carried out, the coating material was found to be very dense. However, the presence of grain boundaries resulted in poor ideal He/N(2) separation efficiencies.     

磁控溅射制备硅铝阻隔膜的研究

采用磁控溅射技术以10%Si～90%Al合金为靶材,通入O2将Si氧化成SiO2,Al氧化成Al2O3,在普通PET薄膜表面制备具有高阻隔性无机阻隔薄膜层,以增加其阻隔性.传统的磁控溅射法制备SiO2膜工艺,大多采用射频溅射法,但其成本较高,效率较低,无法充分满足大面积工业化镀膜生产的需要.而采用10%Si～90%Al合金不仅可以实现直流溅射工艺,而且测量结果表明,薄膜的阻隔性得到大幅度提高.     

Investigation of microstructure and mechanical properties of multi-layer Cr/Cr2O3 coatings

Single and multi-layer Cr/Cr₂O₃ coatings were deposited by reactive magnetron sputtering with the total thickness of 7 μm on steel substrates. X-ray diffraction analysis showed that single and multi-layer Cr/Cr₂O₃ coatings have different preferred crystal orientations. Columnar microstructure was detected by transmission electron microscopy both in metal chromium and ceramic chromium oxide layers. Grain size increased with the coating thickness. The value of single and multi-layer coating's fracture toughness is between 4 and 6 MPa·m^1/2 measured with the Berkovich tip indentation, and it is between 2.8 and 3.9 MPa·m^1/2 when measured with the Vickers indenter. The adhesion is about 192.1 and 246.7 J/m² for single and multi-layer coatings, respectively.     

Fabricating highly active mixed phase TiO2 photocatalysts by reactive DC magnetron sputter deposition

Recent work points out the importance of the solid-solid interface in explaining the high photoactivity of mixed phase TiO₂ catalysts. The goal of this research is to probe the structural and functional relationships of the solid-solid interface created by the reactive DC magnetron sputtering of titanium dioxide. We show that sputter deposition provides excellent control of the phase and interface formation. We explored the effects of the process parameters of pressure, oxygen partial pressure, target power, substrate bias (RF), deposition incidence angle, and post annealing treatment on the structural and functional characteristics of the catalysts. We have successfully made pure and mixed phase TiO₂ films. These films were characterized with AFM, SEM, TEM, and XRD to determine surface morphology, phase distribution and phase content. The performance as photocatalytic surfaces was measured and compared (normalized for surface area) to mixed phase TiO₂ fabricated by other methods, including flame hydrolysis powders, and sol-gel deposited TiO₂ films. The sputtered mixed phase materials were far superior to the commercial standard (Degussa P25) and sol-gel TiO₂ as measured by the gas phase oxidation of the air pollutant acetaldehyde under UV illumination. These results demonstrate that reactive DC magnetron sputtering is a powerful tool for investigating the role of the solid-solid interface in influencing photocatalytic activity. In addition, our work illustrates the feasibility of reactive DC magnetron sputtering as a practical commercial technique for manufacturing highly active nanostructured TiO₂ photocatalysts.     

Residual stress in polytetrafluoroethylene-metal nanocomposite films prepared by magnetron sputtering

In the present research we have evaluated residual stress as well as thermal stability of polytetrafluoroethylene (PTFE) and PTFE-based silver (Ag) nanocomposite films fabricated by dual magnetron sputtering. We used a RF magnetron system for sputtering PTFE, and a DC magnetron sputter source for metal. We have demonstrated that thin nanocomposite films of Ag/sputtered PTFE (thickness 800 to 1100 nm, Ag concentration 3.5 to 24.5%) deposited on silicon are stressed (6.24 to 12.2 MPa). The residual stress depends on the concentration of the nanoparticles. Pure sputter deposited PTFE films are under a small tensile stress, which becomes increasingly more compressive upon increasing the filling factor of the metallic nanoparticles. Depending on the concentration of nanoparticles, the residual stress is determined by a thermal component that is sensitive to temperature variation, even in the range of room temperature. In the evaluation of the thermal response of the nanocomposite-silicon system, both the changes in the thermal expansion coefficient as well as the elastic modulus of the nanocomposite with the concentration should be taken into account.     

A wear-resistant coating—Oxidized graded multilayer TiN/W coating

Combining sputtering technology using an industrial-scale four-target DC closed-field unbalanced magnetron sputtering ion plating system (CFUBMSIPS™) with post heat treatment, a graded multilayer TiN/W coating, consisting of five layers, was synthesized and its outmost W layer was transformed to lubricious WO₃ successfully. The coatings were characterized by using GDOES, GXRD, a Rockwell C indentation tester, a nanoindentation tester, and a scratching tester. Wear behavior of coatings was evaluated by using a pin-on-disc tribometer. Through proper post heat treatment, the multilayer TiN/W coating, in spite of having a lower nano-hardness, showed good adhesion, much better wear performance and lower friction coefficient compared with the reference monolayer TiN coating.     

Novel TiAlCN/VCN nanoscale multilayer PVD coatings deposited by the combined high-power impulse magnetron sputtering/unbalanced magnetron sputtering (HIPIMS/UBM) technology

A new TiAlCN/VCN coating combining high hardness, low friction coefficient and chemical inertness has been developed for dry machining of “Sticky” (Al-, Ti- and Ni-based) alloys as well as advanced Metal-Matrix-Composite (MMC) materials used in aerospace and automotive industries. Excellent performance was achieved due to the synergy between V and C as main coating elements and the nanoscale multilayer structure of the coating. TiAlCN/VCN was deposited by the combined High-Power Impulse Magnetron Sputtering/Unbalanced Magnetron sputtering (HIPIMS/UBM) technology. Macroparticle free V⁺ ion flux generated by HIPIMS discharge was used to sputter clean the substrates prior to the coating deposition. A 0.4 μm thick TiAlN base layer followed by 3 μm thick TiAlCN/VCN nanoscale multilayer coating was deposited by unbalanced magnetron sputtering. The sputtering was carried out in a mixed CH₄, N₂ and Ar atmosphere. In dry milling of Al7010-T7651 alloy, TiAlCN/VCN nanoscale multilayer PVD coating outperformed state of the art Diamond Like Carbon (DLC, Cr/WC/a-CH) coating by factor of 4. In drilling Al-alloy enforced MMC materials, cemented carbide drills coated with TiAlCN/VCN produced 130 holes compared to 1-2 holes with uncoated drills.     

Transmission electron microscopy of nanocomposite CrB-N thin films

This paper reports on the preparation and characterization of CrBN nanocomposite coatings for low friction, low wear and high thermostability applications. Sputtered CrBN thin films were prepared in order to obtain a composite structure consisting of hard CrB₂ and CrN crystallites as well as hexagonal BN lubricant phase by unbalanced magnetron sputtering (UBM) of a CrB₂ target in an Ar/N₂ gas discharge. Coatings, with a total thickness of 4.5-5.5 μm, were deposited at 450 °C on silicon single-crystal substrates. A nanocomposite structure was obtained by increasing the nitrogen content of the sputtering gas. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy. The films were generally found to consist of crystallites of a 1-4 nm size embedded in amorphous matrix. This crystalline phase was identified by electron diffraction as hexagonal CrB₂ for low nitrogen content and cubic CrN for high nitrogen content. In the medium composition range, the structure was amorphous, still keeping the two-phase morphology. The use of high-resolution imaging mode helped to reveal the composition of the amorphous phase which seems predominantly to consist of boron nitride.     

Influence of Deposition Conditions on the Crystal Structure of MoS2 Coating

MoS2 coatings were prepared using an unbalanced bipolar pulsed DC （direct current） magnetron sputtering apparatus under different targets, cathode current densities, power modes and bias voltages. The morphology, structure and growth characteristics of MoS2 coatings were observed and identified respectively by scanning electron microscopy, X-ray diffractometry and mass spectrometry. The results show that MoS2 coatings evolve with the （002） basal plane parallel to the surface by using cold pressed target with lower density, lower cathodic current density, bipolar pulse DC power and minus bias voltage, whereas the coatings deposited under hot pressed target, higher cathodic current density, simple DC power and positive bias voltage have the （002） basal plane perpendicular to the surface. The influence of deposition conditions on the crystal structure of MoS2 coating is implemented by altering its growth rate and the energy of sputtering-deposition particles.     

Reactive deposition of Al-N coatings in Ar/N2 atmospheres using pulsed-DC or high power impulse magnetron sputtering discharges

In this paper, the metal to ceramic transition of the Al-N₂ system was investigated using classical reactive pulsed-DC magnetron sputtering and HIgh Power Impulse Magnetron Sputtering (HIPIMS) at a constant average current of 3 A. Optical emission spectroscopy measurements revealed more ionised aluminium species in the HIPIMS discharge compared to pulsed-DC sputtering. It also showed excited N⁰ and ionised N⁺ species in reactive Ar/N₂ HIPIMS discharges. The corresponding evolution of the consumed nitrogen flow as a function of the N₂ partial pressure revealed that a higher amount of reactive gas is needed to achieve stoichiometric AlN with HIPIMS. Electron probe micro-analysis and X-ray diffraction measurements confirmed that a partially poisoned aluminium target is enough to allow the deposition of stoichiometric hcp-AlN thin films via HIPIMS. To go further in the comparison of both processes, two stoichiometric hexagonal aluminium nitride thin films have been deposited. High power impulse magnetron sputtered hcp-AlN exhibits a higher nano-hardness (18 GPa) than that of the coating realised with conventional pulsed-DC sputtering (8 GPa).     

ZnO/Al2O3 coatings for the photoprotection of polycarbonate

ZnO and ZnO/Al₂O₃ thin films were deposited by r.f. magnetron sputtering on polycarbonate (PC) films in order to protect this polymer against photodegradation. The composition, structure and optical properties of the ceramic coatings were characterised. CO₂-plasma treatments were applied to PC in order to improve the coating adhesion. The PC surface energy was characterised by wettability measurements and the chemical bonds were analysed by XPS.It was found that ZnO coatings improve the stability of PC to UV radiations and that an intermediate alumina coating inhibits the photocatalytic oxidation of PC at the PC/ZnO interface. Additionally an external alumina coating brings a high hardness to the coating.     

Abscheidung von SiOxNy Sperrschichten durch Dual Magnetron Sputtering

Silicon Oxynitride Barrier Layers Deposited by Pulsed‐DC Dual Magnetron Sputtering SiO_xN_y barrier layers have been deposited using pulsed direct current (DC) and medium frequency (MF) sputtering on large area (GEN 5) glass substrates. Several process parameters, such as discharge voltage, boost voltage, and discharge frequency were varied with the goal of increasing system productivity and reducing the arc rate during SiO_xN_y deposition. The arc rate during operation with pulsed DC dual magnetron sputtering was lower than for MF sputtering; however for the same nominal discharge power, the deposition rate using pulsed DC power supplies was slightly lower than for operation with MF. The suitability for use as a barrier layer was deduced by capping the SiO_xN_y layers with DC sputtered ZnO:Al coatings and subjecting the sample stacks to anodic and cathodic degradation and subsequent storage in a damp atmosphere.