Plasma Beam Sputtering Research Articles

The research progress on corrosion and protection of silver layer

In this paper, the mechanism and reason of silver corrosion and discoloration are discussed. The analysis and characterization of silver corrosion layer and the cleaning method of the discoloration part of silver are described. There are two methods for silver anti-corrosion and anti-tarnish. One is to develop anti-discoloration silver alloy. The other is to treat silver layer surface, which includes: surface plating, surface passivation, surface coating (Resin Coating, RC; Plasmapolymer Coating, PC; Organic Adsorption Complex Membrane, OACM; Supramolecular Self-Assembly, SSA), and surface deposition (Megnetron Sputtering, MS; Plasma Beam Sputtering, PBS; Chemical Vapor Deposition, CVD; Atomic Layer Deposition, ALD). It has great potential for SSA and ALD technologies to be applied in the silver corrosion protection. Furthermore, the technological requirements of silver anti-corrosion are listed and the need for silver anti-corrosion to be comprehensively controlled from all aspects is also proposed.

Environmental durability of protected silver mirrors prepared by plasma beam sputtering.

Various overcoat layers have been developed to protect silver mirrors from tarnish and corrosion. However, the mechanisms by which these protective layers improve mirror durability are not fully understood. Mixed flowing gas exposure was used to investigate the corrosion behavior of plasma beam sputtered silver mirrors with different adhesion layer materials. A small amount of nickel in the adhesion layer had a significant impact on the silver-dielectric interface. Additionally, lateral transport of silver was found to be an important factor in the corrosion process. Better stability at all layer interfaces is suggested to improve mirror durability.

Study of Plasma and Ion Beam Sputtering Processes

Study of Plasma and Ion Beam Sputtering Processes

Control of stress in protected silver mirrors prepared by plasma beam sputtering

Plasma beam sputtering was used to deposit dielectric-protected silver mirrors that exhibited excellent durability and controlled stress. The durability of the mirrors was strongly dependent upon the presence of a very thin chromium adhesion layer between the silver layer and the dielectric overcoat. The stress of the five-layer mirror was balanced by controlling the compressive stress in the top dielectric layer, offsetting the net tensile stress of the combination of layers below.

XPS analysis of W xC y thin films prepared by sputter deposition

W x C y thin films with different compositions were studied in order to correlate their properties with the thin-film composition and chemical bonding of C and W atoms. Three W x C y thin films with C concentrations in the range 40–80 at% were deposited on WC–Co substrates by the plasma beam sputtering technique. The composition of the thin films and chemical states of elements were analysed by X-ray photoelectron spectroscopy (XPS) depth profiling. The C and W concentrations in the films were quantified using XPS intensities from a WC–Co substrate with a known composition. The C1s peaks in the high energy resolution XPS spectra of thin films allowed identification of the WC phase and the amorphous carbon phase as a function of the film composition. The results show that the amorphous carbon a-C phase is present in those films with composition x< y. The measured hardness of the films decreases with a decrease of the WC concentration.

A new experimental method for studying the cracking behaviour of PVD multilayer coatings

One way to improve the cracking resistance of PVD hard coatings is to prepare them in the form of a multilayer structure, where micro-cracks tend to branch and deflect at the interface between two alternating layers of different materials. However, it is still not clear how a layer structure influences the cracking resistance. One of the main reasons for the shortage of data in this field is the lack of appropriate experimental methods to prepare the samples and to observe the micro-cracks that appear through the multilayer structure. Due to the extremely small layer thicknesses, a SEM analysis on a perpendicular sample cross-section is too coarse, while a cross-sectional TEM analysis is time consuming and, therefore, expensive. In this study a new experimental method for observating the propagation of micro-cracks in different multilayer structures is presented. It is based on microscopic observations of the micro-cracks on the cross-section of a ball crater over a scratch track. The first step of this test is to prepare a scratch on the sample using a diamond stylus. Next, a ball crater must be ground over the scratch track at the position where the first cracks are observed in the scratch track. Along the edges of the scratch track the low-angle cross-section of the multilayer structure can be observed. On such a cross-section we could clearly see how the micro-cracks propagate from the coating surface through all the layers that compose the multilayer structure. For the inspection of the micro-cracks we used optical as well as SEM microscopy. The applicability of this new technique was tested on a 2.6 μm-thick TiN/CrN multilayer structure with 6, 8, 16 and 32 layers and on a 2.4 μm-thick CrN/TiAlN multilayer structure with 8 layers. The coatings were prepared by reactive sputtering in a Sputron (Balzers) plasma–beam sputtering apparatus. The coating adhesion was characterized with a conventional scratch tester (CSEM Revetest). For the ball–crater preparation we used a steel ball with a diameter of 20 mm and a diamond paste with a grain size 0.25 μm. The ball craters were prepared on the scratch track at the positions that corresponded to the different scratching loads. We discovered that the individual layer structure has a strong influence on the crack propagation as well as on the plastic deformation of multilayer coatings.

Bonding structure of carbon nitride films deposited by reactive plasma beam sputtering

This work is devoted to the study of the reactive plasma beam sputtering deposition of carbon nitride thin films. To investigate the variations of the bonding structure, induced by modifying the main deposition parameters, a systematic characterization of the films by X-ray photoelectron spectroscopy (XPS) is performed. With increasing the nitrogen partial pressure, the deposition rate and the nitrogen atomic fraction in the films increase, and the valence band spectrum shape is modified. The curve fitting of the C1s and N1s peak spectra shows that C and N atoms exhibit several chemical states, representative of different type of chemical bonds.

Carbon nitride thin films deposited by reactive plasma beam sputtering

Carbon nitride thin films have been deposited on silicon substrates by reactive sputtering of a pure graphite target. In this process, argon plasma, generated by a hot cathode discharge, diffuses through a diaphragm into a deposition chamber towards the target which is biased at −300V. The current density on the target is about 30mAcm−2. Nitrogen gas is injected into the deposition chamber during the sputtering. Evolution of the deposition rate is measured versus the partial N2 pressure. The films are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red spectroscopy (FTIR) and Raman spectroscopy. The atomic ratios of N and C in films are evaluated by XPS. At high N2 partial pressure, the atomic fraction saturates at a value of 38at.%. The curve fitting of the C1s and N1s XPS peak spectra indicates that C and N atoms in films exhibit two different chemical states, representative of different CN chemical bonds. These XPS results, combined with FTIR and Raman analysis, suggest the existence of two amorphous carbon nitride phases in films, one with a stoichiometry similar to C3N4 and the other with an increasing fraction of nitrogen as the total N content in the films increases. These two carbon nitride phases seem to be present as soon as nitrogen is incorporated in films, even at low atomic concentration of nitrogen.

Titanium Zirconium Nitride by XPS

Titanium zirconium nitride (Ti0.53Zr0.47N) coatings have been deposited on polished steel substrates by dc reactive sputtering in a Sputron (Balzers AG) plasma-beam sputtering apparatus at 200 °C. A thin intermediate layer of TiZr (0.08 μm) was deposited between the substrate and the 2.8 μm thick TiZrN coating. The deposition rate was 12 nm min−1. The partial pressure of nitrogen was 3 × 10−2 Pa, while the total working pressure was 2 × 10−1 Pa. Using a planetary substrate holder with double rotation, thickness and composition uniformity better than 2% were obtained. The average roughness, Ra, of the substrate was &amp;lt;0.04 μm, whereas after the deposition Ra values between 0.06 and 0.08 μm were measured for TiZrN coatings. The XPS measurements were performed in an Escalab 200-X spectrometer (VG Instruments) using nonmonochromatized Al Kα radiation from a twin Mg/Al anode operating at 300 W. The hemispherical energy analyzer was operated in the CAE mode with a constant pass energy of 20 eV. In the present paper the following spectra are presented: survey spectrum, spectra of major elements titanium, zirconium, and nitrogen (Ti 2p, Zr 3d, and N 1s), spectra of minor elements oxygen and carbon (O 1s and C 1s), and valence band spectrum. Spectra were background subtracted using a Shirley method. Peak positions and widths were determined by least squares fitting.

Oxidation behaviour of TiAlN coatings sputtered at low temperature

The basic mechanical and structural properties, as well as the oxidation behaviour of Ti 1- x Al x N coatings sputtered at low temperature are reported. Ti 1- x Al x N coatings of four different compositions were sputter deposited in a Sputron (Balzers) plasma-beam sputtering apparatus at a temperature below 200°C. Polished tool steel discs, silicon wafers and polished alumina ceramics were used as substrates. Oxidation of coatings was carried out by heating the samples at temperatures of 700–900°C in an oxygen atmosphere for selected times. The surface and fracture cross-sectional morphology of the as-deposited and oxidized films were studied by scanning electron microscopy, while the structure of the coatings was examined by the XRD and TEM techniques.

Characterization of (Cr,Ta)N hard coatings reactively sputtered at low temperature

Two (Cr,Ta)N coatings with different composition were deposited in a Sputron plasma beam sputtering apparatus at a temperature below 200°C on polished tool steel disks, polished alumina substrates and silicon wafers. Microhardness, adhesion and internal stress were measured by Vickers microindentation, the scratch test and sample deflection, respectively. The mechanical and electrical properties were compared to the values of CrN and TaN binary nitride coatings prepared in the same device under similar conditions. Like CrN and TaN, (Cr,Ta)N crystallizes in a cubic (NaCl) structure. Oxidation resistance was tested in the temperature range 550–850°C. We observed that a chromium-rich protective oxide layer developed on the Cr 0.58Ta 0.42N coating, while on the Cr 0.17Ta 0.83N coating the oxidation was more rapid, with cracks appearing at temperatures as low as 600°C.

Oxidation of ternary TiZrN hard coatings studied by XPS

Electrochemical and thermal oxidation of TiZrN hard coatings deposited by the plasma beam sputtering technique are investigated using x-ray photoelectron spectroscopy (XPS). Ternary TiZrN coatings are found to be more susceptible towards oxidation compared to binary TiN and ZrN coatings. Electrochemical oxidation results in the formation of a mixed Ti(N,O)+Zr(N,O) oxynitride layer in the lower potential range (up to 1.1 V), whereas at higher potentials a mixed TiO2+ZrO2 oxide layer is formed. This layer still incorporates a certain amount of nitrogen released during transformation of nitride to oxide. A similar is observed in the case of thermal oxidation at 350–600°C, where the main product is a mixed TiO2+ZrO2 layer. Nitrogen, which should normally be evolved during oxidation, remains incorporated in the growing oxide layer. No tendency towards alternate layer formation, i.e. ZrO2/TiO2, was observed under the experimental conditions investigated. © 1998 John Wiley & Sons, Ltd.

Zirconium Nitride by XPS

Zirconium nitride (ZrN) coatings have been deposited on polished steel substrates by a plasma-beam sputtering technique in a Sputron apparatus (Balzers A. G.) at 200 °C. A thin intermediate layer of Zr (0.08 μm) was deposited between the substrate and the 2.8 μm thick ZrN coating. The average roughness, Ra, of the substrate was &amp;lt;0.04 μm, whereas after the deposition Ra values between 0.06 and 0.08 μm were measured for ZrN coatings. Coatings exhibit a fine grain structure of the grain size &amp;lt;100 nm. The XPS measurements were performed in an Escalab 200-X spectrometer (VG Instruments) using non-monochromatized Al Kα radiation from a twin Mg/Al anode operating at 300 W. The hemispherical energy analyzer was operated in the CAE mode with a constant pass energy of 20 eV. In the present paper the following spectra are presented: survey spectrum, spectra of major elements zirconium and nitrogen (Zr 3d and N 1s), spectra of minor elements oxygen and carbon (O 1s and C 1s), and valence band spectrum. Spectra were background subtracted using a Shirley method. Peak positions and widths were determined from a least squares fitting procedure.

Chromium Nitride by XPS

Chromium nitride (CrN) coatings have been deposited on polished steel substrates by a plasma-beam sputtering technique in a Sputron apparatus (Balzers A. G.) at 200 °C. A thin intermediate layer of Cr (0.08 μm) was deposited between the substrate and the 2.8 μm thick CrN coating. The average roughness, Ra, of the substrate was &amp;lt;0.04 μm, whereas after the deposition Ra values between 0.06 and 0.08 μm were measured for CrN coatings. Coatings exhibit a fine grain structure of the grain size &amp;lt;100 nm. The XPS measurements were performed in an Escalab 200-X spectrometer (VG Instruments) using non-monochromatized Al Kα radiation from a twin Mg/Al anode operating at 300 W. The hemispherical energy analyzer was operated in the CAE mode with a constant pass energy of 20 eV. In the present paper the following spectra are presented: survey spectrum, spectra of major elements chromium and nitrogen (Cr 2p and N 1s), spectra of minor elements oxygen and carbon (O 1s and C 1s), and valence band spectrum. Spectra were background subtracted using a Shirley method. Peak positions and widths were determined from a least squares fitting procedure.

Titanium Nitride by XPS

Titanium nitride (TiN) coatings have been deposited on polished steel substrates by a plasma-beam sputtering technique in a Sputron apparatus (Balzers A. G.) at 200 °C. A thin intermediate layer of Ti (0.08 μm) was deposited between the substrate and the 2.8 μm thick TiN coating. The average roughness, Ra, of the substrate was &amp;lt;0.04 μm, whereas after the deposition Ra values between 0.06 and 0.08 μm were measured for TiN coatings. Coatings exhibit a fine grain structure of the grain size &amp;lt;100 nm. The XPS measurements were performed in an Escalab 200-X spectrometer (VG Instruments) using non-monochromated Al Kα radiation from a twin Mg/Al anode operating at 300 W. The hemispherical energy analyzer was operated in the CAE mode with a constant pass energy of 20 eV. In the present paper the following spectra are presented: survey spectrum, spectra of major elements titanium and nitrogen (Ti 2p and N 1s), spectra of minor elements oxygen and carbon (O 1s and C 1s), and valence band spectrum. Spectra were background subtracted using a Shirley method. Peak positions and widths were determined from least squares fitting procedure.

Hard coatings on soft metallic substrates

The application of PVD CrN coatings onto soft, electropolished nickel moulds and PVD TiN, CrN and double-coating (TiN + CrN) onto copper welding contact tips is reported. Both studies and tests were made in practical conditions, i.e. in industrial manufacturing. The first case study was on protection of the surface of a precision mould with a complicated shape and used for artificial tooth production. The substrate was 4 mm thick Ni, electrodeposited and electropolished. Such a sensitive surface is used together with polymethylmethacrylate paste in a tooth production pressure process at 150°C. We found that in this case, the only feasible deposition technique was DC reactive sputtering of Cr and CrN at 140°C in the SPUTRON plasma beam sputtering equipment of Balzers. A 3 μm thick CrN coating with high microhardness (1400 HV, 0.25 N on the Ni substrate), good adhesion ( L c AE= 12-16 N) and excellent corrosion and oxidation resistance, successfully protected the nickel mould from mechanical damage occuring during production cycles, even after its use for 18 months. The second case was improvement of copper welding contact tips used in the MIG welding technique. TiN and CrN coatings were used both as single and double coatings, directly deposited on the copper substrate and also using 5 and 16 urn thick Ni galvanic coatings as an intermediate layer. Good adhesion ( L c AE=15–22 N), low scratching coefficient, high microhardness (1400–2500 HV, 0.10 N) and temperature resistance up to 600°C (TiN) or 800°C (CrN and TiN + CrN) provided an improvement in welding contact tip life from the standard value of 10–16 h of interrupted work to 85–210 h. The best results were obtained with the “hard” tip substrate made of CuZnZr alloy. For all substrate-coating combinations — various substrate quality and applied coatings — the abrasion wear of the electrode wire was predominant, while any welding material stuck onto the coated contact tip was easy to clean off.

High-temperature oxidation of TiN/CrN multilayers reactively sputtered at low temperatures

The high-temperature (600–850°C) oxidation of multilayer hard TiN/CrN coatings was investigated. TiN/CrN multilayer coatings (2.6 μm thick) with modulation periods in the range 83–425 nm were deposited at low temperatures (150°C) onto polished tool steel discs and polished alumina ceramic substrates ( R a = 25 nm) using the plasma-beam sputtering technique. The oxidation rate was obtained from the weight gain as a function of the oxidation time. The activation energy for oxidation of TiN/CrN multilayers was determined and compared with that for CrN, TiN and CrTiN coatings. The depth profiles of samples oxidized at various temperatures were examined by Auger electron spectrometry (AES) and glow discharge optical spectrometry (GDOS) to determine the thickness and the composition of the oxide layer. The morphology of the oxidized coatings was investigated by scanning electron microscopy (SEM). Continuous in-situ electrical resistivity measurements were performed on the same coatings to detect grain-boundary oxidation. The adhesion and microhardness of the multilayers were also determined.

Industrial applications of CrN (PVD) coatings, deposited at high and low temperatures

Abstract Industrial applications of CrN (PVD) coatings are entering an expanding but selective range of mass manufactured goods. They may be prepared as single, low and high temperature CrN coatings and double TiN+CrN coatings. In this work, depositions of CrN at high temperatures were performed by a low voltage thermionic arc in a BAI 730M apparatus, while at low temperatures (below 250 °C), the plasma-beam sputtering process in a SPUTRON apparatus was used. We studied the following critical parameters that influence the quality of the coatings and applied the performance tests used in industrial practice: adhesion and scratching coefficient, microhardness, surface topography, oxidation and corrosion resistance. The performance tests were made with the assistance of technicians as well as in 12 Slovenian factories. CrN coatings were deposited at 480 °C for wear and corrosion protection in cold forming and cutting of copper in commutator manufacturing, in forming of aluminium components in automotive production and for surface improvement of moulds (made of H11 steel) in Al-Si die casting under pressure. Deposition temperatures of 180–220 °C, obtained in the SPUTRON apparatus, were required to improve cold forming tools made of alloyed tool steels (e.g. D2 and D3). The lowest obtainable temperature of 140 °C in the SPUTRON gave a CrN coating of high quality for practical use. These coatings were used to protect electrodeposited and electropolished nickel moulds (models) in artificial teeth production. Double TiN+CrN coatings were used as a highly abrasive resistant coating in the production of rotors (in the electromotor industry), and in cold forming and forging in mass manufacturing of screws. The results and performance tests were compared with the available data, mostly published on forming, milling, deep drawing of copper, nickel and titanium and their alloys, and on die casting of aluminium and Al-alloys.

High temperature oxidation of thin CrN coatings deposited on steel

Chromium nitride coatings were deposited on steel substrates by the tetrode plasma-beam sputtering technique at 200 °C. The coatings exhibit a dense, smooth, and homogeneous structure with the appearance of occasional pinhole defects, as shown by scanning electron microscopy (SEM) and atomic force microscopy. The thickness of the coatings was sufficiently small (0.34 μm) to allow the study of the compositional changes induced by the high temperature oxidation throughout the oxide and nitride phases, as well as at the inner interface between the nitride coating and the substrate. The CrN coatings were oxidized in an oxygen flow at temperatures up to 750 °C. After oxidation at temperatures higher than 450 °C the formation of a Cr2O3 layer as a separate phase on the top of the nitride coating is observed. It is suggested that the mechanism of CrN oxidation proceeds by the progressive replacement of nitrogen by oxygen. As the temperature is raised the thickness of the Cr2O3 layer increases and its grain structure becomes more pronounced. Besides oxidation of CrN to Cr2O3 another parallel process is taking place, namely the oxidation of iron from the substrate. This process leads to the formation of FeO islands, which represent defect spots on the surrounding Cr2O3 surface. The number of these defects depends on the temperature and time of oxidation. In order to study the failure mechanism, various surface analytical techniques were applied, i.e., x-ray photoelectron-spectroscopy, Auger electron spectroscopy, energy dispersive x-ray spectroscopy, and SEM. It is suggested that the penetration of iron through the coating starts at the pinholes present in the coating. At higher temperatures, however, this is not the dominating mechanism, and the diffusion process is further facilitated by the mismatch in the thermal expansion coefficients between the substrate and the nitride coating. Thermal stress thus established leads to the loss of adhesion at the inner substrate/coating interface and therefore creates additional paths for the diffusion of iron.

Novel applications of CrN (PVD) coatings deposited at 200 °C

CrN (PVD) coatings, deposited at 200 °C in plasma beam sputtering apparatus, were used for selected applications in industry. Using CrN coating, we improved two types of tool: moulds for Al alloy die casting (made of AISI H11 tool steel) and cold forming tools (made of AISI D2 and D3 tool steel). For the first group of tools, it was important that the CrN coating could be successfully used as a hard, oxidation- and corrosion-resistant coating at working temperatures of up to 800 °C; for the second group of tools, the low tempering temperature dictates deposition at 200 °C. The tool life, surface quality of the products and wear mechanisms were studied for the following polished tools (max. diameter, 210 mm): a mould for Al-Si12 die casting of small components of compressors; a combined cold forming and cutting die for mass production of covers for the heating plate of an electric stove; a cold forming deep drawing die for the production of a halogen lamp housing in the electric light industry; a tool set for automatic gradual deep drawing of fancy goods for the shoe and leather industry; a deep drawing die for mass production of the covers of electric motors. All the results show that a CrN coating 4.5–5.5 μm thick with a Cr intermediate layer 0.2 μm thick between the substrate and the coating improved the technological processes and resulted in a noticeable improvement in performance tests. Increased tool life, a higher quality of surface finish of the products and high reliability of CrN coated tools in production were regularly observed during long-term performance tests.