Ion Plating System Research Articles

Effects of processing parameters on the microstructure and hardness of the arc ion-plated TiN on a type 304 stainless steel

Substrate bias and specimen-to-target distance are two important parameters that can be manipulated during preparation of TiN films using a cathodic arc ion plating system. Experiments were carried out to deposit TiN on a type 304 stainless steel for different cathode biases ranging from 100 to 300 V and specimen-to-target distances from 150 to 175 mm. Characterization of the microstructure of the TiN-coated steel was done both by transmission and scanning electron microscopy. The results show that the thickness of the TiN coatings increases with decreasing specimen-to-target distance. The TiN coatings exhibit a tapered columnar microstructure and the cone shape of the grains is influenced by the substrate bias. The resistance to deformation of the TiN coatings was evaluated by a Vickers microhardness indenter. It is found that the hardness of the coatings, ranging from 2200±40 to 1880±10, decreases with specimen-to-target distance for different substrate biases ranging from 100 to 300 V.

A study on the synthesis and microstructure of WC–TiN superlattice coating

WC–TiN superhard coatings are formulated to form a nanoscaled superlattice by separate arc reactive evaporation of Ti and WC. The microstructure of WC–TiN films was identified to be a superlattice of TiN and β-WC 1− x phases with modulation period (λ) of 5–13 nm and the lattice planes were continuous through the TiN and β-WC 1− x layers. The residual stress of WC–TiN films was measured to be 7.9 GPa. This high stress was reduced to 2.2 GPa by introducing Ti or Ti–WC interlayers. Ti–WC interlayer also increased the film adhesion strength. In spite of almost the same residual stress of 2.2–2.3 GPa, Ti–WC/WC–TiN film showed a higher adhesion strength of 48.5 N than that of Ti/WC–TiN film. These results are attributed to the low residual stress and higher stiffness of the Ti–WC interlayer than the soft Ti interlayer. The microhardness of Ti–WC/WC–TiN film on cemented carbide was measured to be 40 GPa and the maximum hardness was obtained as the period (λ) was approximately 7 nm. This value is approximately 1.5 times higher than that of the TiN single layer film. Other WC–TiN superlattice coatings with Ti and WC interlayers showed a hardness range of 38–40 GPa. The ratio H 3/ E 2 (plastic deformation resistance) of WC–TiN superlattice films with various interlayers was calculated to be in a range from 0.18 to 0.33. This paper reports the preparation of WC–TiN superlattice coatings on WC–Co and Si substrates using a multi-cathode arc ion-plating system. The microstructures and mechanical properties of WC–TiN superlattice films were investigated, too.

Steel coating by self-induced ion plating, a new high throughput metallization ion plating technique

Ion plating techniques present major advantages for continuous steel coating in terms of throughput and product quality when compared, respectively, to sputtering and vacuum evaporation techniques. However, the ion plating systems available on the market today are cumbersome and have technological problems that prevent immediate implementation in high throughput air-to-air continuous steel coating plants. To address these problems, we have developed a new ion plating technique, referred to as “self-induced ion plating,” in order to produce continuous coating on flat products. This technique is based on the generation of a magnetron discharge in the sputtered and evaporated vapor produced by a tin cylindrical target. Very high deposition rates were achieved (⩽220 μm/min) with moderate values of the electrical mean power density (⩽45 W cm−2) applied to the tin target. The magnetron configuration reduced material side losses by reducing the metal escape zone area on the target side. Another feature of this technique is that the control of the heat transfer between the target and its backing plate allows control of the target surface temperature, and hence control of the sputtered and evaporated material fractions.

MgO thin film formation by ion enhanced deposition processes

MgO thin films were prepared by ion plating systems and by an ion beam sputtering system with a plasma filament type ion source. Triode-type and rf ion plating processes were employed. MgO films were prepared with various oxygen partial pressures ranging from 10−3 to 10−2 Pa. In the triode-type ion plating process, the MgO(200) was the preferred growth orientation of film. In the rf ion plating process, MgO(111) and (220) reflection peaks appeared in the x-ray diffraction patterns of films. The films were transparent, and those values of transmittance of ultraviolet region were increased as increasing oxygen partial pressure. In the ion beam sputtering process, the film showed amorphous structure and low transmittance.

A study of the structural and mechanical properties of Ti=MoS2 coatings deposited by closed field unbalanced magnetron sputter ion plating

The closed field unbalanced magnetron sputter ion plating system has been used to produce MoS2 coatings by co-deposition of Ti and MoS2. Previous results have shown that the coatings are harder than pure MoS2 coatings and that they show very low coefficient of friction and longer lifetimes. These Ti=MoS2 coatings show excellent wear resistance at high loads. The coefficient of friction is as low as 0.02 at a relative humidity of 40%, and conventional adhesion scratch tests indicate critical loads in excess of 120 N. This paper presents a study of the composition, structure and mechanical properties of these metal=MoS2 composite coatings using several analytical techniques (RBS, ERDA, XRD, scratch test, SEM and EDS). The analytical results are discussed and related to the mechanical properties of the coatings.

Ion beam analysis and Raman characterisation of coatings deposited by cosputtering carbon and chromium in a closed field unbalanced magnetron sputter ion plating system

A novel non-hydrogenated a-C coating has been deposited by sputtering carbon and chromium targets in a closed field unbalanced magnetron sputter ion plating system, with a metallic adhesion layer between the substrate and the cosputtered layer. The properties of these new carbon coatings have been previously compared with those of more conventional hydrogenated metal-containing DLC. Reciprocating and pin-on-disk friction and wear tests have shown that the new carbon coatings have a lower friction coefficient and that their wear resistance is more than one order of magnitude higher than metal-containing hydrogenated DLC coatings.This paper presents an initial study of the composition and structure of these new coatings. Rutherford and Non-Rutherford backscattering of alpha particles and protons are used for studying the stoichiometry and for the determination of impurities. Elastic recoil detection analysis (ERDA) is used for depth profiling of hydrogen. Raman spectroscopy is used to investigate the structure of the different carbonaceous layers.

Plasma diagnostics of triode ion-plating systems by energy-resolved mass spectroscopy and comparison of TiN film properties

Plasma properties related to TiN deposition are compared in two triode ion-plating systems (System A and System B) using a low-voltage arc discharge. System A employs a magnetic field, confining the arc and the plasma, while System B does not. The systems also differ in the configuration of the chamber.TiN coatings are deposited in both systems over a range of negative bias voltages from 25 to 150 V. A correlation is established between the coating properties and the plasma parameters determined by energy-resolved mass spectrometry.The plasma potential in System B is between +15 and +35 V, featuring a spatial inhomogeneity. System A exhibits a higher plasma potential (about +55 V), resulting in higher energies of ions at substrates and a narrower energy distribution of ions. Unlike in System B, the population of Ti2+ in System A is even higher than that of Ti+. The presence of high-energy neutral Ti is observed.The texture coefficients and the stress-free lattice parameters measured by X-ray diffraction on TiN films deposited at negative substrate bias in the range from 25 to 150 V behave similarly in both deposition systems but with a shift in bias necessary for similar properties. The appropriate bias in System B is about 75 V higher than in System A. This shift corresponds to the difference between the systems in the plasma potential and the degree of ionisation found by energy-resolved mass spectrometry.Other film properties, especially the film compressive stress, microhardness, critical load in scratch tests and the surface roughness, remain almost constant over the whole range of bias values in both systems. This means that these properties are less sensitive to ion bombardment in the triode ion-plating systems under the conditions studied.

Energy and mass spectroscopy studies during triode ion plating of TiN films in two different layouts

Abstract Plasma properties are compared in two triode ion-plating systems using a low-voltage arc discharge. The systems differ in the configuration of the chamber and magnetic field. Mass and energy distributions of positive ions during deposition of TiN films were measured by an energy-resolved mass spectrometer. Plasma parameters were determined also by Langmuir probe diagnostics. In both systems, single and multiple charged ions of Ar and N2 gas and the evaporated Ti were detected. The system with a strong magnetic field confinement exhibits a higher plasma potential (Up=55 V) under standard deposition conditions, the peak ion energy is higher and the energy distribution is narrower than in the system without magnetic confinement (Up=12 to 35 V). The probability for the multiple charged ions in this system is much higher than in the system without the magnetic confinement, so the population of Ti++ in this system is even higher than that of Ti+. The presence of high-energy neutral Ti is also observed.

MoS2/metal composite coatings deposited by closed-field unbalanced magnetron sputtering: tribological properties and industrial uses

Abstract In the past, MoS 2 coatings deposited by sputtering have consisted of a first few layers with a dense coherent structure followed by an open columnar structure, with only the first few layers providing any wear resistance. The high ion-current densities at low substrate bias voltages, characteristic of the closed-field unbalanced magnetron sputter ion-plating system, produce MoS 2 coatings that are dense, coherent and adherent with very good tribological properties. The tribological properties of these coatings have been tested by using reciprocating and pin-on-disc friction and wear machines, and the results are presented. The properties of the coatings were improved by optimising the deposition parameters, in particular by reducing the amount of water vapour present in the atmosphere of the coating system. It has been found that the properties can be further improved by the co-deposition of small amounts of metal with the MoS 2 . The equipment and deposition methods are described. The MoS 2 /metal composite coatings were harder, much more wear-resistant and also less sensitive to water vapour in the testing atmosphere. They gave excellent wear resistance at loads as high as 140 N on the reciprocating wear tester using a 6 mm diameter WC pin. The coefficient of friction was as low as 0.02 at a humidity of 40%, and the coatings and adhesion scratch tests indicated critical loads of >120 N. The composite coatings have been studied by micro hardness testing, scratch adhesion testing, pin-on-disc and reciprocating friction and wear tests. The structure of the coatings was studied by optical microscopy and scanning electron microscopy of normal sections and taper sections produced by ball cratering techniques. Some applications, including the coating of cutting and forming tools, are described.

Plasma diagnostics in a triode ion plating system*

Langmuir probes combined with an energy resolved mass analyzer make satisfying contributions to the characterization of plasmas. The probes provide spatially resolved information on the well known plasma parameters, while the mass analyzer gives information on the energy distribution functions for ions/neutrals originating from some point in the plasma volume. These diagnostic tools have been used to investigate the glow discharge of the triode ion plating system of Balzers (BAI 640), a physical vapor deposition installation for the production of hard coatings. Two identical, planar Langmuir probes, positioned in the main argon plasma body, and an energy-resolved mass analyzer (Balzers PPM 421), directed to the crucible, were used to investigate the influence of the four most important process parameters, i.e., (1) the low voltage (LV) arc current, (2) the high voltage (HV) electron gun current, (3) the total pressure, and (4) the substrate voltage on the plasma parameters and on the energy spectra of ions and neutrals, during the evaporation of titanium without reactive gases. The substrate bias had no significant influence on the plasma parameters and on the energy spectra, but is very important for the microstructure of the thin film. The HV electron gun, used to melt the titanium, changed the plasma parameters only at high current values, but the energy spectra of the Ti ions changed drastically. The LV arc current and the total pressure are the process parameters that do affect both the probe characteristics and the energy spectra of ions and neutrals.

Mechanical and microstructural changes of magnetron sputtered TiN films with various magnetic field configurations

TiN coatings were deposited in a single magnetron sputter ion plating system in “balanced” and unbalanced mode with a closed magnetic field configuration. The film microhardness, thickness, adhesion, microstructure, preferred orientation and topography were analyzed as a function of the substrate position inside the deposition volume. In the static deposition mode and under the limitations of the experimental set-up used, no real homogeneous deposition conditions were achieved, but a significant possibility of controlling the spatial distribution of deposition conditions was demonstrated. The variation of the coating microhardness over the target-to-substrate distance, d S–T, ranging from about 80 to 210 mm was acceptable for practical applications, while the critical load for adhesive failure was found to decrease significantly with increasing d S–T in a balanced magnetron configuration. The variation of magnetic field configuration provided a relatively homogeneous distribution of the bias current density over the deposition volume, but the preferred orientation of the coating was changed from (200) to (111) with increasing d S–T. The energy delivered per unit volume of growing film, S E, and bombarding ion to deposited metal atom flux ratio j i/ j m were considered. It was found that j i/ j m can be used to describe qualitatively the change of preferred crystalline orientation of coatings.

Properties of diamond-like carbon films deposited by ion plating with a pulsed substrate bias

Diamond-like carbon films of high quality were deposited using CH4 by a magnetically enhanced ion plating system with a bipolar pulsed substrate bias (0–1000 V, 0–33 kHz). The flux and energy distribution of impinging ions could be individually controlled by the bias voltage and the duty cycle, defined as the percentage of ion acceleration time in the total pulse period. The effects of bias voltage and duty cycle on the structure and properties of film were studied. Owing to charge accumulation on the surface, ion bombardment energy increases with decreasing the duty cycle. The film's hydrogen content decreases with decreasing the duty cycle. The film having the highest growth rate and the lowest internal stress can be obtained at a duty cycle of 88%, suggesting possible charge neutralization on the surface. In addition, the hydrogen content decreases with increasing the substrate bias and the film having the highest growth rate and high hardness can be deposited at a substrate bias of 600 V. A lower bias reduces the ion flux and ion energy forming a softer hydrogen-containing film, and a higher bias induces the re-sputtering effect and the formation of sp2 carbon bonding in the film. Hardness and adhesion increase with increasing the substrate bias, except that hardness slightly decreases at the highest bias of 800 V, owing to the extremely high ion energy bombardment enhancing the formation of sp2 bonding. Ion energy is concluded to be crucial in determining the structure and properties of diamond-like carbon films.

Preparation of a new tetragonal copper oxynitride phase by reactive magnetron sputtering

Cu–O–N layers were deposited on Si-〈100〉 wafers at a temperature of 90°C in a reactive magnetron sputtering ion plating system (R-MSIP). For this, a Cu-target was sputtered by a nitrogen/oxygen plasma, and the influence of the oxygen partial pressure on composition, structure, and texture of the Cu–O–N layers was investigated. The analyses of the films with EPMA, XRD, and HEED yielded the following results: with an appropriate setting of the oxygen partial pressure, the oxygen content of the Cu–O–N layers could be controlled between 2.4 and about 50 at. %. Structure analyses have shown changes in the crystal structure of the films with increasing oxygen and decreasing nitrogen content from the simple cubic (sc) structure of Cu 3N, followed by a two phase region, where the sc structures of Cu 3N and Cu 2O appear, to a single phase film with the sc structure of Cu 2O. With an oxygen content of 43.6 at. % a new Cu–O–N phase with the tetragonal structure of paramelaconite (≈Cu 12 2+Cu 4 +O 14) and the composition Cu 27O 22N was grown. The film with an oxygen content of about 50 at. % consists of monoclinic CuO.

TiN hard coating prepared by sputter ion plating system with facing target sputtering source and RF discharge

A new type sputter ion plating system with facing target sputtering source and RF discharge has been developed for hard coating of metals and various compound materials. In this system, the plasma density of 10★–10★ cm is obtained in the discharge space, and the electron temperature is in the range of 3–6 eV. Moreover, the incident ion energy on the substrate can be controlled by the sheath potential of the de bias applied to the substrate. The adhesive force of the TiN thin film prepared by this system on the stainless steel substrate is in the range of 20–50 N at the scratch test. The adhesive force, Vickers hardness, preferred oriemation and resistivity of the TiN thin film are influenced significantly by the dc substrate bias voltage. Moreover, by controlling the RF power the concentration ratio for Ti and N can be controlled.

Influence of the plasma current to Ti-melt on the plasma parameters and microstructure of TiN coatings in the triode ion plating system

TiN coatings have been deposited by triode ion plating in a mixture of Ar and N 2 with a varying total current through the melt. The observed energy spectra of ions and neutrals are discussed with respect to the plasma parameters measured with Langmuir probes. The current I Pm from the plasma to the Ti-melt in the crucible was modified from 0 A up to 100 A. As I pm is increased, major effects on the plasma and on the film microstructure (preferred orientation, stress-free lattice parameter, residual stress, thickness and microhardness) were observed. The positive voltage of the melt UR with respect to the ground increased from 0.1 to 29 V. The plasma potential (positive voltage with respect to ground) of the main plasma body increased from 4 to 16 V, while the electron temperature ranged from 2.5 to 4 eV. Plasma density and floating potential is also discussed. A high energy tail appeared in the energy distribution function of some neutral and ionic species, especially for neutral and ionized evaporated Ti. At high values of I pm the energy distribution of both highly energetic Ti + and neutral Ti goes up to 25 eV and 30 eV. At low values of I pm the majority of the Ti + ions are thermalized. The microstructure of the deposited TiN films develops from porous structures, with low compressive or even tensile stresses at I pm =0 A, up to dense structures, with high compressive stresses of more than 15 GPa at the highest value of I pm . Possible explanations of the observed effects are discussed, based on plasma ionization processes close to the melt and in the plasma body.

Estimation of density of charge species in a triode discharge system

Triode discharges are widely used in plasma assisted physical vapour deposition techniques to enhance ionisation even under low pressures. In addition to this, the triode discharges enable independent control of substrate bias currents irrespective of bias voltage and pressure, compared to magnetron discharges. One of the problems associated with triode discharge is non-uniform distribution of plasma density. The extent of non-uniformity depends on the size of the chamber, characteristics of the thermionic filament, location of the electrodes with respect to one another, operating potentials at the electrodes, and pressure. Hence it is necessary to carry out the discharge studies to study space charge distribution in the chamber. A Langmuir probe is used in the present study, to estimate the density of ions and electrons for different triode discharge currents, substrate bias voltages, pressures and at different locations in the plasma in a triode ion plating system. It has been observed that the uniformity of the density of the charge carriers depends on the operating conditions.

Influence of magnetic field configuration on the deposition conditions in an unbalanced magnetron system

Three configurations of a magnetron sputter ion plating system were considered: the double magnetron open field configuration, single magnetron multipole open field configuration and single magnetron multipole closed field configuration. The (Ti,Al)N coating was deposited in the double magnetron system onto substrates oscillating in and out of high ionization degree plasma obtained by overlapping two magnetron discharges. A strong influence of plasma “density” on the coating growth was found. The experiments were also performed in two single magnetron systems in order to find approximately the region in which a plasma suitable for coating deposition is generated. A rough estimation of high density plasma pattern was given based on voltage-current characteristics of the magnetron discharge. Both single magnetron systems were found suitable for hard coating deposition, but the higher bias current density at the substrate surface had been measured in closed field configuration under similar deposition conditions.

The processing and testing of new and advanced materials for wear resistant surface coatings

In the search of wear resistant coatings for applications such as cutting tools and turbine refurbishing, we have produced and tested a wide range of coatings including nanocrystalline metals (At, Ti, Cu), nanolaminated composites, containing alternating layers of metal-ceramic (Al 2O 3 and Ti/TiN) or metal-metal (Ti/Cu), and monolithic coatings (TiN). These coatings were produced using an r.f. magnetron sputtering system except for the monolithic TiN which was commercially produced using an ion plating system. All these coatings were tested for their tribological (friction and wear) and mechanical (hardness) properties using a pin-on-disc type wear rig and an ultra-microindentation system, respectively. The tribological properties that were used to compare the relative performance of these materials were the coefficients of friction (both peak and steady-state) and the wear rates (volume loss per unit sliding distance) in both the severe and mild wear regimes. The optimum combination of a low coefficient of friction and low wear rate in the steady-state regime was exhibited by Ti/TiN nanolaminated composite coating with a 150 nm Ti layer thickness and a 20 nm TiN layer thickness. This material also exhibited the highest hardness of the composite coatings. The micromechanisms responsible for the differences in hardness and wear resistance of these materials are discussed and recommendations are made on future directions for producing improved wear resistant coatings.

Effects of oblique energetic bombardment on the morphology and microstructure of triode ion plated titanium films

The effect of angle of incidence of ions, varied between 45° and 90°, generated in a triode ion plating system on the morphology and microstructure of titanium films, has been investigated. It has been found that intensity of reflections, lattice parameters, stress, and grain size are strong functions of the angle of incidence of the ions. The same properties were studied for their variation with bias voltage between 0 and 2 kV at a constant substrate bias current of 10 mA. It was found that the intensity of the (002) reflection increases with an increase in angle of ion incidence up to 60°. The lattice parameter and stress reach a minimum while the grain size goes through a maximum at this value. All the films show a tensile stress independent of deposition parameters. To isolate the effects due to ion bombardment the films have been coated in high vacuum, in a diode mode, and finally the triode configuration. It has been conclusively found that the angle of incidence of ions is very important in controlling properties and growth of the films.

Relative importance of bombardment energy and intensity in ion plating

For ion plating and similar plasma assisted physical vapor deposition processes, the relative significance of bombardment energy and intensity during film growth is poorly understood in relation to their effects on certain coating properties. In this article, we report on the results of a study on the microstructural properties of copper coatings deposited by a thermionically supported ion plating system with an electon beam evaporation source. By carefully selecting the deposition conditions, analysis of the coatings has provided the following conclusions: First, provided that a critical bombardment energy is exceeded, increasing bombardment intensity is more important than increasing the energy at the growing coating surface to attain maximum coating densification for minimum bombardment power. For copper coatings, the critical energy is approximately 200 eV. Second, we have identified sputtering as the main mechanism responsible for material redistribution during coating growth. We suggest that coating densification resulting from energetic bombardment may be characterized in a structure zone model by a parameter representing the proportion of arriving material which is sputtered during deposition.