ICMCTF2010 Session BP: Symposium B Poster Session

In a previous study, the effects of substrate vertical positioning for TiAlN films deposited using an unbalanced inverted cylindrical magnetron sputtering system were analyzed. Results indicated that, due to the unbalanced magnetic fields, the substrates at the different axial locations in the deposition chamber were exposed to varying ion bombardment rates. This variation created a competition among re-sputtering, amorphitization, and atom surface diffusion, and the results of this competition affected the final film properties. Preliminary evidence also shows that the substrate’s radial location at a given axial position also affects the film’s composition. The TiAlN films for this study were deposited on glass and silicon substrates. The substrates were positioned on a vertical platform between the two targets at three different radial distances (0, 50, and 120 mm from the central axis of the targets). In addition, at each distance the substrates were positioned at three different angles (0, 45, and 60˚ measured from the vertical platform). Titanium and Aluminum cylindrical targets were used and the sputtering power during deposition was maintained at 2 kW for each target. The argon and nitrogen gas flow rates were kept at 75 and 40 sccm, respectively. No biasing voltage was applied during deposition. The films’ elemental compositions at the different radial distance were analyzed using energy dispersive X-ray spectroscopy. The X-ray diffraction measurements were used to determine the crystal structure of the films. Scanning electron microscope images were used to indicate the morphology for all samples.

Hard coatings based on Ti_1-xAl_xN and Cr_1-xAl_xN are well established and routinely used for various industrial applications due to their outstanding properties like high hardness, wear and corrosion resistance. While TiN and CrN crystallize in the cubic B1 structure, AlN is stable in the wurtzite B4 form. Consequently, there exist cubic (low AlN mole fraction) and wurtzite (high AlN mole fraction) stability ranges. It has been shown that the desired coating properties for machining and wear protective applications are obtained for their cubic allotrope. It is therefore of great interest to understand how various parameters affect the stability range of the cubic phase.

Ab initio calculations of the total energy for the cubic and wurtzite phases allow to estimate the maximum mole fraction, x_max, of AlN while maintaining the desired cubic phase of the Ti_1-xAl_xN and Cr_1-xAl_xN systems. In this paper we investigate the influence of pressure on x_max. Both systems exhibit a strong dependence of their cubic and hexagonal phase stability ranges on the applied pressure, or the inherent build-in stresses. Under a compression of 4 GPa an increase in x_max by 0.1 AlN mole fraction is obtained for both systems, Ti_1-xAl_xN and Cr_1-xAl_xN . Consequently, stress-related effects cannot be neglected in the discussion of the wide spread of the experimental estimations of x_max.

Researches on multilayer films to extend the life of cutting tools have been widely reported and have shown distinct results. In this research, TiAlN/CrAlYN/TiAlN three-layer films were deposited by conventional cathodic arc ion plating (AIP) method from two alloyed targets of TiAl and CrAlY. The designing of three-layer film was carried out based on the following factors; a) top-layer TiAlN for improvement in hardness and abrasion, b) middle-layer CrAlYN for improvement in oxidation resistance, c) base-layer TiAlN for improvement in adhesion strength to substrate. From past researches, the advantage of yttrium(Y) addition has been proposed [1] and similar results have been observed in our laboratory. However, the Y-added films show lower hardness compared to Ti-based nitrides because of the Cr-based nitrides. Therefore, if it is possible to increase the hardness of the Y-added film further possibility will arise for these films to be used in cutting tools. The effect of layering to hardness and oxidation resistance of the film was investigated by X-ray, electron microscope, and micro-hardness analysis. For comparison, monolayer TiAlN and CrAlYN films were deposited.

The three-layer film showed a high hardness of 28.4 GPa, even with insertion of softer CrAlYN with a hardness of 22.8 GPa. As a result, this would substantially reduce the abrasion for this three-layer film. The oxidation resistance was investigated by annealing the samples in air at 700,800,900 °C for one hour. X-ray results revealed that the three-layer films showed better oxidation resistance than TiAlN film. The three-layer film even annealed at 900 °C, showed strong peaks of nitride still existing . Hence, it was indicated that TiAlN/CrAlYN/TiAlN three-layer film was able to exploit the benefits of TiAlN monolayer film and CrAlYN monolayer film. Further oxidation experiment of the three-layer film is evaluated by cross-sectional observation and in-depth elemental distribution analysis by SEM and GDOES.

[1] F. Rovere, P. H. Mayrhofer, A. Reinholdt, J. Mayer, J. M. Schneider, Surf. Coat. Technol., 202, (2008) 5870.

This study reports on the tribological characterization of TiAlSiN quaternary films deposited by cathodic arc evaporation PVD techniques, and the effects of the testing temperature on the wear mechanisms. The coatings have been produced in a commercial METAPLAS PVD chamber equipped with 6 arc sources. The coatings were deposited on mirror polished DIN 1.2344 hot work steels. Ti and AlSi cathodes were simultaneously evaporated at different arc currents and N₂ total pressures, in order to obtain different film properties. The micro-structure of the coatings has been evaluated using electron microscopies and x-ray diffraction techniques. All the films exhibited dense fine grained cubic fcc poly-crystalline microstructures. It was observed that the films exhibited lesser intense diffraction features as the aluminum content increased.

The plastic hardness of the coatings depends on the film chemical composition. Thus values between 39 GPa and 27 GPa were measured. The tribological tests have been conducted in a ball on disc configuration at room temperature, 200ºC, 400ºC and 600ºC using alumina balls as counter surfaces. At room temperature, the TiAlSiN films show wear rates comparable to these characteristics of TiN or TiAlN coatings, tested under the same conditions. Conversely, the wear rates of the TiAlSiN coatings measured at 200 and 400ºC are lesser than this measured at RT. In fact, the alumina balls worn off significantly during the tests, whilst the wear tracks on the coated discs were barely measurable. At 600ºC, however, a significant wear rate was observed. These results may be consistent with the formation of an oxide surface on the contact area that enhanced the wear resistance of the films when tested at high temperatures.

Finally, TiAlSiN coated hard metal curved surfaces have been tested against stainless steel (AISI316) planar counter surfaces to evaluate both, the wear of the coatings, and the adhesion of Fe on the hard metal surfaces. The rate of wear and adhesion will be compared with previous coating materials such as CrN, or gradient CrCN studied under similar experimental conditions [1].

References

[1] G.G. Fuentes, M.J. Dí­az de Cerio, J.A. García, A. Martínez, R. Bueno, R.J. Rodrí­guez, M. Rico, F. Montalá, Y. Qin. Surface and Coatings Technology, 203 (2008) 670

In this study, the superlattice CrN/AlN coating was synthesized by using unbalanced magnetron sputtering technique, using Cr (99.95wt%) and Al (99.95wt%) elemental cathodes which is improve the limit of the electroplate CrN with the ultrahigh hardness and have excellent oxidation resistance. When applied to cast Al-alloy melt into molded parts, aluminum die casting was always faced harsh conditions, such as corrosion, erosion and surface damage problem. Many of aluminum die casting dies have to bear high temperature at 600^oC. The CrN coating was replaced the hard chrome plating for the environmental. The application of the single layer was only allowed under 600^oC, which can’t effectively meet the conditions for the use of aluminum alloy die casting dies.

The microstructure and mechanical properties of the coatings were analyzed by using the transmission electron microscopy (TEM), X-ray diffraction(XRD), scanning electron microscopy (SEM) X-ray photoelectron spectroscopy (XPS), and molten Al alloy dipping test was also conducted to evaluate the performance of CrN/AlN coating by wear test.

AlN is a very well know very wide bandgap semiconductor which exhibits absorption in the far UV spectral range, while being purely transparrent in the visible spectal region. In addition, it has excellent mechanical properties and substantial chemical and metallurgical stability. The combination of its properties makes AlN a promising matrix material for multifunctional, self-monitored coatings and/or durable optical sensors based on metal nanoparticles embedded into AlN and exhibiting surface plasmon resonance (SPR).

In this work we deal with the growth of AlN nanocomposite films with Ag inclusions (AlN:Ag) on Si(100) and polycrystalline sapphire by Pulsed Laser Deposition (PLD) and dual-cathode confocal magnetron sputtering. The films' structural properties, such as nanoparticle size and distribution, were studied in relation to the growth method and the used parameters. High resolution transmission electron microscopy, x-ray diffraction, and optical reflection spectroscopy (ORS) were employed in order to determine the film composition, inclusions' crystal structure and the optical properties, respectively. In-situ Auger Electron Spectroscopy (AES) has been used for the chemical analysis of the grown films.

We investigate the thermodynamic and the kinetic factors that determine the phase separation and the formation of nanocomposites or the dilution of Ag into the AlN matrix. Especially in the case of sputter-deposited films we investigate two growth approaches: (a) co-deposition of Ag and AlN using two magnetron sources, and (b) multilayer sequential growth of AlN and ultra-thin Ag layers (as thin as to approach the island coalescence threshold) and post-growth annealing.

The employed Ag nanoclusters had average sizes ranging between 3-10 nm. The critical parameters determining the nanoparticle size and distribution and the decisive role of the latter on the optical performance of AlN:Ag nanocomposite films are established. Thus, ORS has revealed that strong SPR exist in films with well defined metal inclusions of narrow size distribution.

Chromium incorporated amorphous carbon (a-C:Cr) coatings were deposited onto silicon substrates by cathodic vacuum arc deposition using a Cr target in an Ar/C₂H₂ gas mixture atmosphere. A linear magnetic shield was employed to reduce the macroparticle density in the films. Various negative bias voltages ranging from 50 to 450 V were applied to the substrates. The effectiveness of the magnetic shield was studied by atomic force microscopy (AFM). X-ray diffraction (XRD) analysis showed that amorphous structures are formed in all cases. High resolution transmission electron microscopy (HRTEM) revealed a nanocomposite structure with chromium carbide particles embedded in a carbon matrix. X‑ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to determine the carbon bonding and to study the presence of different forms of free amorphous carbon. The Raman spectra were decomposed into four single Gaussians and the results are discussed in terms of the ratio of the areas of the two D bands to the areas of the two G bands, I(D)/I(G). The results showed that the I(D)/I(G) ratio is proportional to the negative bias voltage.

Acknowledgements

This work has been supported by the Programa Nacional de Materiales of the Spanish Ministry of Education under proyect: MAT2006-13006-C02-02

Ceramic hard coatings are commonly applied as protective overcoats on tools and components to enhance their performance. Although most nitride coatings deposited by physical vapour deposition (PVD) are chemically inert, one of the main obstacles for wider application has been the sensitivity to crevice corrosion and higher costs compared with electrochemically deposited coatings. Regardless the various applications of CrN-based systems, their decomposition routes and oxidation behavior is still not well resolved in literature.

In the present study the thermal stability and corrosion performance of arc-evaporated nanocomposite Cr-B-N coatings deposited from CrB_0.2 compound targets at 500°C in a commercial Oerlikon Balzers RCS system are explored. During synthesis the total pressure (Ar+N₂) was kept constant at 2 Pa, while the N₂ fraction was varied between 0 and 1 (0, 0.15, 0.25, 0.5 and 1). Differential scanning calorimetry (DSC) studies in Ar up to 1500^oC using different heating rates give a deeper understanding of the decomposition kinetics for the materials under study as a function of nitrogen content. In the as-deposited state, coatings are nanocrystalline with Cr and Cr₂B phases without nitrogen addition, with a Cr(N) solid solution, Cr₂B and Cr₂N at 0.15 N₂, and finally with CrN and an amorphous BN phase at N₂ fractions above 0.5, respectively. Coatings deposited at low N₂, namely 0.15 N₂ and 0.25 N₂, revealed exothermic DSC peaks at 750^oC, corresponding to film recovery and recrystallization processes. The decomposition for coatings deposited at 0.5 and 1 N₂ starts at 1000^oC with a phase transformation of fcc-CrN to hcp-Cr₂N. These results corroborate with thermogravimetric analysis (TGA) mass losses observed. For studying the oxidation behaviour, DSC/TGA studies up to 1500^oC were conducted in an O₂/Ar atmosphere. The differences observed, attributable to different structure, morphology and composition among the coatings investigated, are discussed.

The corrosion resistance of CrB_xN_y coatings, studied using potentiodynamic corrosion tests in 3.5% NaCl aqueous solution, is higher than the uncoated steel substrate, with passive behaviour over a large voltage range (−200 to +700 mV). Nanocomposite CrB_xN_y coatings deposited at 0.5 N₂, and consisting of nc-CrN+a-BN phases show the lowest passive current density of 7×10−6 A cm⁻² (8×10⁻⁵A cm⁻² for CrN).

The CrN top layer with NiP-based interlayer was deposited on AISI 420 stainless steel with magnetron sputtering system. The variation in microstructure of the CrN, NiP-based, and dual coatings were controlled by process and post-annealing temperatures. The corrosion behavior the CrN/NiP-based composite coating in 3.5M NaCl solution was investigated by electrochemical impedance spectroscopy (EIS). The results of Nyquist and Bodes curves showed that there was a correlation between the electrochemical properties and corrosion mechanism of CrN/NiP-based composite coatings. In particular, the amorphous and crystallized structure of the NiP interlayer was significantly different. The interfacal reactions between the solution and CrN top layer or the CrN top layer and NiP-based interlayer could be explained with the equivalent circuit models. The corrosion resistance of the dual CrN/NiP-based coating could be enhanced through microstructure control on the NiP-based interlayer.

In order to protect structural steels (SS) used in fast neutron high temperature reactors from radiation induced defects and improve their resistance to irradiation-induced embrittlement, ceramic-based protective coatings are investigated as potential candidates. Among other materials, transition metal nitride coatings exhibit large hardness (> 20 GPa), chemical inertness, structural and thermal stability and may therefore be envisaged as a material of choice to surround the fuel. Preliminary measurements have been performed on Ti-Zr-N coatings to study their resistance to Xe ion irradiation at relatively low energy (360 keV), as Xe is a main product of reaction fissions in nuclear reactors.

In this study we investigate the resistance of Ti-Zr-N and Ti-Cr-N coatings to harsh environnements, including exposure to corrosive media and ion irradiation. Ti-Zr-N films, with thickness of~ 1 μm, were deposited by either dc reactive magnetron sputtering or vacuum cathodic arc deposition on SS and stainless steel substrates. The composition and crystalline structure of the as-deposited coatings was analyzed by energy dispersive analysis of X-rays (EDX) and X-ray diffraction (XRD), respectively. Ion irradiation with He, Kr and Xe ions in the range 20 keV-200 MeV was performed at the Nuclear Center of Kazakhstan. The effect of the ion fluence on the resulting structure, surface morphology and mechanical properties is reported. Electrochemical potentiodynamic polarization method was used to test the corrosion resistance of these coatings in acidic and basic media.

Crystallographic texture in thin films, i. e. the preferred orientation of particular crystal planes relative to the film substrate, is a common feature in thin films. Since many of the materials properties (dielectric constant, elastic modulus, etc) are typically anisotropic, the properties obtained for thin films depend on the preferred orientation (PO). For metal nitrides, such as niobium nitride (NbN), it has been shown that the preferred orientation results as a combination of different deposition parameters; thickness, plasma density and ion energy [1]. These parameters affect the overall free energy of the film, i. e,. the balance between surface and strain energy defining one PO and in consequence the film properties are modified. Most of the studies reporting the change in the PO of hard metal nitride thin films use cross-section transmission electron images to demonstrate that the PO changes from [100] to [111] as the thickness increases. In this work, we have deposited 2 μm NbN thin films by magnetron sputtering and by doing grazing angle X-ray diffraction (XRD) at different incidence angles (1 to 16°), it was possible to observe the variation in the preferred orientation. The spectrum at very low incidence angle shows that the 2 μm film has a mixture PO [111] plus [100] with a intensity ratio close to 1:1. As the incidence angle increased, the intensity of the [100] increased, while the [111] decreased, so the ratio was 10 to 1. This result suggest that for the deposition conditions used, 2 microns is close to the critical thickness where the PO changed from [100] to [111]. Similar studies were done for NbN films of different thickness to show that using grazing angle XRD as a function of the incidence angle, it is possible to study the evolution of the preferred orientation in thin films. The mechanical properties of the NbN films were also studied by nanoindentation and correlated to the XRD data.

[1] S.E. Rodil, J.J. Olaya, S. Muhl, B. Bhushan, G. Wei. Surface & Coatings Technology 201 (2007) 6117–6121

In this work we propose the simultaneous ablation of two different targets in a reactive atmosphere in order to prepare thin films of a ternary compound. Particularly, titanium carbonitride (TiCN ) thin films were deposited combining two crossed plasmas, produced ablating titanium and graphite simultaneously, in an Ar/N₂ atmosphere. Films were deposited at room temperature onto Si (100) and AISI 4140 steel substrates. Individual and combined plasmas were characterized, in the substrate position, by the Optical Emission Spectroscopy and Langmuir probe techniques in order to determine the plasma parameters, that is to say, the excited species present in the plasmas, the mean kinetic ion energy and the plasma density. In these experiments, the parameters of the titanium plasma were kept constant, meanwhile the parameters of the carbon plasma were varied in order to study their influence, on the char acteristics of the deposited films . The structure and composition of the films have been analyzed by X-ray Diffraction, Raman Spectroscopy and Elastic Forward Analysis. Mechanical properties, such as nanohardness, and adhesion of the films were also measured. The experimental results showed that the TiCN films can be deposited in the form of a composite of small TiN crystallites inmersed in a amorphous CN matrix, or it can form the TiCN compound, depending on the plasma parameters used in the experiment. It was found that the hardness increases with the carbon ion energy and plasma density, reaching a maximum hardness of about 33 GPa.

Various thermal managements of HB LEDs have been reported; however, the study in regard to the machinery tools for MCPCB is relatively less. This work prepares the tungsten carbide (WC) cement cutters coated with TiAlN, ZrCN, CrCN or their nanocomposite layers via the filtered cathodic arc ion plating (FCAIP) process and the cutters are subsequently applied to the machining of Al-core MCPCBs using a computer-programmable router. Physical properties and microstructures of cutters were also investigated by the pin-on-disc tribometer, grazing incidence x-ray diffraction (GIXRD), transmission electron microscopy (TEM), energy dispersive x-ray spectrometer (EDS) and nanoindentation so as to elucidate the performance of cutters. Poor results were observed in traditional TiAlN- and ZrCN-coated cutters that a built-up edge in the cutters occurred due to the high friction feature of Al core of MCPCB and coating layers. Though the CrCN coating with low friction coefficient benefited the cutter life, good cutting quality was hardly obtained due to its low hardness. As to the multilayer-coated cutter, up to 5-time improvement of tool life was achieved by the CrCN/ZrCN/CrCN-coated cutter in comparison with the coating-free cutter. This is ascribed to the low friction coefficient and high hardness features of the CrCN/ZrCN/CrCN nanocomposite layer which effectively improves the performance and tool life of cutter.

Due to the consideration on carbon reduction to protect environment, in this study, CO₂ gas and titanium target were adopted to synthesize Ti-C-O composite coatings on AISI 304 stainless steel by a cathodic arc deposition system with various CO₂ gas pressures. Coating morphology and properties such as coating structure, adhesion strength, hardness/elastic modulus (H/E) ratio, and abrasion behaviors were analyzed to evaluate the effect of CO₂ pressure on the coating performances for the surface modification on AISI 304 stainless steel. The results showed that the composite coatings mainly consist of TiO and DLC mixed phases. Moreover, when the pressure of CO₂ was controlled at 5 mtorr, the coatings had a lower Ra value, higher adhesion strength (HF1), and higher H/E ratio. Sequentially, the optimum coated specimen produced with the CO₂ pressure of 5 mtorr showed an outstanding wear resistance as compared to the uncoated and the other coated ones.

The outstanding properties of ZrO₂ as a 'tough' ceramics are based on its martensitic phase transformation from tetragonal to monoclinic. The ability to control phase formation during synthesis is therefore a prerequisite to exploit the full potential of this material. This has been investigated in detail for bulk synthesis of ZrO₂ and a similar attempt is made here for deposition of ZrO₂ coatings by reactive magnetron sputtering. Using metallic Zr targets in an argon/oxygen atmosphere and sapphire substrates, coatings showing the stable monoclinic ZrO₂ can be synthesized. Formation of the monoclinic phase occurs independent of substrate heating (up to 500°C) and/or application of a pulsed bias voltage at the substrate (up to -100 V at 250 kHz). To synthesize coatings of the high temperature tetragonal and cubic phases of ZrO₂ two different approaches have been investigated: doping with yttria and reactive sputtering in the presence of nitrogen.

For bulk synthesis doping with rare earth metal oxides is a well known method to produce fully stabilized ZrO₂ in its cubic modification and also partially stabilized ZrO₂, which contains a mixture of the cubic and tetragonal phase. Here, a series of coatings with varying yttria content are deposited by magnetron co-sputtering from two metallic targets and one yttria-stabilised ZrO₂ target in an argon/oxygen atmosphere. With this deposition setup the whole range of phase compositions from monoclinic to tetragonal/cubic coatings via phase mixtures can be synthesized and the necessary yttria content to partially or fully stabilise the sputtered ZrO₂ coatings is determined by elastic recoil detection analysis.

An alternative method for tailoring the structure formation in reactively sputtered ZrO₂ films is the use of nitrogen as an additional reactive gas. It is not the incorporation of nitrogen into the coatings, but the target surface coverage with nitrogen that affects the structure formation. This allows for deposition of mainly tetragonal/cubic ZrO₂ coatings without significant amounts of additional elements in the coatings. Reported for the first time by Severin et al. in 2008 this is a new and exciting way not only to control the structure formation but also to stabilise the reactive sputtering process. This is shown to work effectively and coatings produced via this route and via the classical dopant route are compared with respect to structure, chemical composition, intrinsic stresses and grain size.

ZrO₂ coatings are often used for thermal barrier coatings due to their high oxidation resistance and good thermal stability. Previous X-ray diffraction (XRD) analysis indicated that there are two major phases (monoclinic and tetragonal phase) in ZrO₂ coatings, and the compressive residual stress caused by ion-peening effect during deposition processes may control phase transition. Previous literatures reported that corrosion resistance is strongly related to microstructure, phase transition, thickness and packing density of the ZrO₂ coatings. By adjusting O/N ratio, the structure and phase transition of ZrO₂ thin films can be controlled. The goal of this research is to perform a systematic study of the microstructure, packing density and the phase transition of ZrO₂ film and correlate the structure of the coatings to the corrosion resistance. In this study, ZrO₂ thin films were deposited on AISI 304 stainless steel substrate by hollow cathode discharge ion plating (HCD-IP) method. The coatings showed high packing density, good adhesion and high corrosion resistance. The preferred orientation and phase fraction were measured by XRD. The microstructure and thickness were examined by scanning electron microscopy (SEM). The residual stress was determined by modified sin²ψ X-ray diffraction method. The packing density was obtained from the data by Rutherford backscattering spectroscopy (RBS). The corrosion resistance was evaluated using potentiodynamic polarization scan and salt spray test. In addition, the results in this study were compared with ZrO₂ coatings deposited by unbalanced magnetron sputtering (UBMS).

Consistent with previous work in the literature, preliminary results indicate that lower pulse frequencies produced higher deposition rates and more dense films. In addition, films produced with the DC power supply were more dense than those produced with the AC power supply. X-Ray Diffraction (XRD) results indicated the presence of alpha alumina in most films as a mixed phase, with little dependence on power supply or pulse frequency. Scanning Electron Microscope (SEM) results showed increasing surface roughness with increasing pulse frequency.

Alpha alumina has many chemical and mechanical properties that make it an ideal candidate for cutting tool coatings and bio-medical applications. In previous work, we have deposited low-temperature (480C) alpha-alumina with a chrome template layer, and low-temperature (480C) mixed-phase alumina coatings without a chrome template layer using an AC inverted cylindrical magnetron sputtering system.

In this work we report on the systematic deposition of alumina films as a function of power (4-6kW), pressure (2-8mTorr), substrate bias (DC and pulsed), and oxygen partial pressure (35-75%). 39 total runs were performed and several substrates were used (glass, silicon, stainless steel, and a titanium alloy). Analysis of each film included XRD, SEM and TEM. Results indicate strong presence of the alpha phase at 5-6kW, 50% oxygen partial pressure, pulsed bias, and 2mTorr. The presence of alpha alumina has been indicated by TEM and corroborated by XRD. Both characterization methods show mixed-phase films with substantial amounts of alpha alumina. In general, pure aluminum films are observed at lower oxygen partial pressures. At lower powers, little alpha alumina is observed as the energy at the substrate is too low. Indicating noticeable pressure dependence, films deposited at lower pressure (2mTorr) tend to exhibit phases fairly independent of power and oxygen partial pressure. Initial evidence suggests that the deposited films have a weak dependence on substrate bias.

α alumina (Al₂O₃) possesses exceptional mechanical properties, chemical inertness and oxidation resistance, and therefore extensively serve as protective coating. Among the metastable Al₂O₃ polymorphs, γ-Al₂O₃ exhibits wear performance comparable to that of thermodynamically stable α-Al₂O₃ phase and therefore, it is often considered as an alternative to α-Al₂O₃, when low deposition temperatures are required. However, the metastable nature of γ-Al₂O₃ limits the applicability at high temperatures.

In order to design γ-Al₂O₃ films with improved stability, the identification of atomistic mechanisms that determine the phase stability is of importance. Here, we investigate the effects of composition and microstructure on the thermal stability of γ-Al₂O₃ films grown by filtered cathodic arc (FCA) and plasma assisted chemical vapor deposition (PACVD) on TiAlN coated WC cutting inserts.

The as deposited PACVD films have a porous microstructure. 2at.% Cl that originates from the incomplete disassociation of the AlCl₃ precursor used for the growth is detected. The FCA films exhibit a fully dense microstructure. Combining the Differential Scanning Calorimetry (DSC) and X-ray diffraction analysis, we have determined a direct γ to α Al₂O₃ transformation for FCA films at a temperature of 1074°C and for PACVD films at 1023°C. Thermogravimetric analysis and desorption measurements suggest that mobilization of Cl and further release of Cl₂ gas from the PACVD films happen at ~1020°C.

TEM analyses at the interface between PACVD γ alumina and TiAlN interlayer indicates that, after annealing in air, the Al₂O₃/TiAlN film architecture is maintained at the transformation temperature.

On the other hand, in FCA films, the decomposition and further oxidation of the TiAlN interlayer occurs prior to the γ to α transformation, Based on these results, we suggest that Cl desorption in PACVD films may enhance the bulk diffusivity and therefore facilitate the γ to α phase transformation．In the case of FCA films, the γ to α transformation is promoted by the decomposition of the TiAlN into the cubic TiN and hexagonal AlN phases

Highly wear resistant alumina coatings are of significant interest for the application as a metal cutting tool. Motivation for depositing a film in the ternary system Al-Cr-O is to obtain the thermo dynamical most stable alpha phase by alloying with chromium.

For the film deposition a dual magnetron system is used to overcome the hiding anode effect and to increase the ionization and the deposition rate. Metallic aluminum and 30at% chromium alloyed aluminum targets are used to fabricate two samples with different stoichiometric compositions. A detailed phase analyses is essential for understanding the deformation of the film. Transmission electron microscopy analysis is the method of choice for the demanding analysis of the nanocrystalline microstructure.

The mechanical properties are probed by indentation experiments and FIB prepared cross section SEM images of an indent to represent the fracture behavior of the thin films. This demonstrates the advantage of the PVD thin film in comparison to coarse grained alumina film.

As a result the combination of TEM bright and dark field images highlight a microstructure with a grain size of 30-80nm being strongly disordered. The electron diffraction pattern of the alumina and chromium alloyed alumina thin films are characterized by the same typical background signal combined with broad reflections corresponding to the same d-value. Note that only d_hkl-spacings smaller than 0.2 nm appear and that for smaller scattering angles no reflections are observed rather an intensity distribution typical for amorphous structures is found.

TEM-EDX is done locally with a spot size of 25nm showing a solid mixture chromium and alumina (AlCr)₂O₂ of the argon containing thin film. To our knowledge the disorder of the microstructure has not been described until now. However, in the literature the solid mixture of (AlCr)₂O₃ in the corundum structure is well established even at a deposition temperature within the miscibility gap of the phase diagram.

Thickness dependence of metal-insulator transition (MIT) properties was studied on vanadium dioxide for revealing epitaxial growth mechanism and the relationship between the MIT and the crystal structure. Vanadium dioxide with the thickness of 30, 60, 100 and 230 nm, respectively, were deposited on c-plane sapphire substrate by pulsed laser deposition technique. For the structural analysis, x-ray, scanning electron microscope (SEM), Transmission electron microscopy (TEM) and resistance measurement were carried out. X-ray diffraction patterns and TEM images show that b-axis of vanadium dioxide is normal to the surface of the substrate. This indicates that vanadium dioxide grows epitaxially on the sapphire substrate, even though the grain structure is observed on SEM images. Moreover, Grain size and the transition width near 68^oC increased with the thickness, and which were demonstrated that the thickness of vanadium dioxide thin films plays important role in their electrical characteristics. The film with the thickness of 230 nm has the transition width of ~ 9.3 ⅹ 10⁴ near transition temperature.

We present our recent experimental results on the formation of "off-axis texture" and crystallographic tilting of crystallites that takes place in nanocomposite and nanostructured thin films of transition metal nitrides. This appears by the inclination of preferred orientation and the formation of texture along high indices lattice planes like (113) and (115) contrary to conventional monolithic thin films that develop a preferred orientation following to low indices close-packed planes like (111) and (200).

X-ray diffraction techniques were used to characterize the state of stress and development of texture in TiAlN-based single layer and multilayer films deposited on Si (100) substrate using pulsed DC magnetron sputtering. Depositions were carried out under both normal and oblique angle of incidence. The reciprocal space maps around (200) reflections revealed a subtle oscillatory behaviour of the lattice spacing versus curves, which seems to be dependent on the magnitude of the stresses in the films. Pole figure XRD measurements showed that the preferred orientation of the crystallites exhibits cylindrical symmetry but it is inclined with respect to the sample surface. Moreover, the inclination angle of the (002) diffracting planes increases with the increase of the residual stress in the coating.

The results are analysed with respect to the classical growth theories taking into account the role of atomic shadowing, biaxial alignment, and crystallographic defects in particular nanotwin faults that develop in the lattice of growing crystal and change the stacking sequences of atom layers. Lowering the scale of structural and compositional periodicities in PVD thin films activates nanoscale mechanisms such as spinodal modulation, pseudomorphic stabilisation, compositional intermixing, and elastic aniostropies that influence nucleation and growth mechanisms and thereby film properties as measured by nanoindentation.

Refractory metal alloy coatings have been widely used as protective coatings on glass molding dies. The formation of intermetallic compounds in the coatings inhibits grain growth at high temperature environment in the mass production of optical components. In this study, Ta-Ru binary alloy coatings with Cr interlayer were deposited on silicon wafers and cemented tungsten carbide substrates by DC magnetron sputtering processes at 400^oC. The as-deposited Ta-Ru coatings possessed a hardness of 11 Gpa and a surface roughness of 1.2-1.5nm. The oxidation resistances of the Ta-Ru coatings were evaluated by annealing in an oxygen containing atmosphere at 600 ^oC. Preferential oxidation of Ta in the Ta-Ru coatings was verified by X-ray photoelectron spectroscopy and the formation of tantalum oxides on the surface was observed by transmission electron microscopy. After annealing treatment, the variations in crystalline structure, hardness, surface roughness and chemical composition profiles in depth were intensively investigated.

RuN thin films have been investigated as candidates for barrier layers in semiconductor Cu damascene processes. In this study, RuN thin films were deposited by the magnetron DC sputtering in N₂ and Ar atmospheres on Si and dielectric substrates. In order to study the thermal stability of RuN films, the as-deposited RuN films were annealed by rapid thermal annealing (RTA) and then the film resistance was in-situ measured by four-point probe that embedded in the RTA tool. After RTA annealing, an effusion of N occurred inducing changes in the crystallization of RuN and a sharp decrease in the sheet resistance. The x-ray diffraction data showed that the RuN phase was gradually disappeared and the Ru phases were enhanced. The RuN film had better barrier property than that of Ru, even though N was effused from RuN through annealing. The agglomeration of the RuN thin films was evaluated to guarantee the thermal stability during the post-deposition annealing. Besides, the agglomeration reaction of the RuN films under the nitrogen ambient in the RTA process and the different interactions of RuN between Si and dielectrics were also intensively investigated. It was found that the agglomeration behaviors were affected by the N content of the RuN films owing to the surface energy difference and interface lattice mismatch. Furthermore, the RuN films were able to act as a Cu plateable diffusion barrier layer for the advanced Cu-metallization technologies. Cu deposition may or may not occur competitively with the oxide reduction. In the case of the thin resistive oxide-covered RuN seed layers, the “terminal effect” further exacerbated the difficulties in obtaining a compact and fully coalesced Cu film because the rate of Ru oxide reduction was decreased along with the density of Cu nuclei. The Cu deposition must be accounted for Ru oxidation that is sensitive to its microstructure.

Light metal matrix needs to improve mechanical properties such as wear resistance, elastic modulus, and strength, for possible applications in automobile industry [1,2]. One of possible ways is to reinforce ceramic particle into the matrix. Therefore, in order to achieve these properties, the reinforcement phase must be well dispersed in the matrix. In this work, titanium carbide (TiC) particles were coated with aluminum (Al) to enhance the dispersion of the TiC particles into a molten metal based on Al, inducing the improvement of the mechanical properties and the thermal stability of the matrix. Aluminum nitrate (Al(NO₃)₃), as a precursor of Al, was added in the aqueous solution with the TiC particles. The coating of Al on the TiC particles is driven by attractive force between TiC particle with negative charge density and Al with cation in base aqueous solution. Heat treatment under H₂ gas was conducted to obstruct oxidation reaction of TiC particles coated with Al. Powder prepared was characterized by X-ray diffractometry, energy dispersive X-ray spectroscopy, and scanning electron microscope. The Al particle coated on the surface of TiC particles is significantly increased with decreasing the size of TiC particle, resulting from higher specific surface area. The content of Al on the surface of TiC particle is affected by the concentration of Al(NO₃)₃. The TiC particles of 4 and 40 μm are well-coated with Al particles, showing Al and TiC phases, whereas the TiC particle of 20 nm indicates three different phases such as Al, TiC, and TiO₂ (titanium oxide) formed by the oxidation of the TiC. The particle size is important factor to fabricate the Al coated TiC particle without oxidation reaction.

Complex metallic alloys (CMAs) represent an emerging field in materials science. They are defined as intermetallic compounds possessing a large unit cell containing a high number of atoms, usually ranging from some tens to a few thousands. We have shown recently, by resorting to different techniques under ultra-high vacuum (STM, XPS, LEED) that g-Al₄Cu₉ could be favourably used as a buffer layer to accommodate the strain between a quasicrystalline thin film and a metallic substrate [1]. In this work, we investigate the possibility to grow a quasicrystalline thin film in the Al-Cu-Fe-B system by PVD. Optical emission spectroscopy is chosen to identify the emissive species of the plasma in a PVD reactor equipped with three targets.

In a first step, we show the possibility to grow by PVD different phases in the Cu-Al system, especially the g-Al₄Cu₉ phase. We chose to deposit different thicknesses of each element and to anneal the deposited stack to get a homogeneous film with a controlled composition.

In a second step, Cu, Al, Fe, Al₆₃Cu₂₅Fe₁₂ and Al_59.5Cu_25.3Fe_12.2B₃ (in atomic percent) targets are used. Thin films are deposited in an Ar-10vol.%H₂ mixture at various powers and their composition is determined by Energy Dispersive X-ray analysis. Next, optical emission spectroscopy is used to identify the different emission lines in the plasma from 280 nm to 950 nm. UV emission of boron atoms could not be reached. We did not observe any difference, except in the intensity of the transitions, in the spectra for the Al₆₃Cu₂₅Fe₁₂ and Al_59.5Cu_25.3Fe_12.2B₃ targets. Finally, we discuss the possibility to control the composition of the layers and to monitor the process by OES.

[1] T. Duguet et al., J. Phys. : Cond. Matter, 20 (2008) 314009.

In this study, we investigate the effects of the embedded metal layer on reversible resistive switching (RS) behaviors of Ga₂O₃ memory thin films. The Ga₂O₃/metal/Ga₂O₃/Pt structures are fabricated in sequence followed by a 600^oC post-annealing, where the 4 kinds of the embedded metal layers (Cr, Cu, Pt, and Mo) exhibit a thickness of 2 nm. According to the X-ray diffraction (XRD) patterns, the Ga₂O₃ films remain amorphous before and after post-annealing, which is also confirmed by the high-resolution transmission electron microscope (HR-TEM) observation. Moreover, secondary ion mass spectroscopy (SIMS) depth profiles indicate the metal diffusion within the Ga₂O₃ films. There is no high-voltage forming process required in all the memory cells, showing extra high voltage is unnecessary in the control circuits. Based on the results of the successive RS cycles, the memory cell with embedded Pt layer shows the most stable RS behaviors, compared with the cells with embedded other three metal layers. The endurance test is performed over 2000 cycles, and there is no data loss found in the non-destructive readout test under 0.3V. The aforementioned results demonstrate the possible application memory of the Ga₂O₃ memory thin films with embedded metal layer.

Ion energy distributions of sputtered Si particles have been measured by an energy-resolved mass spectrometer, and the results are correlated with measured thin film properties. The plasmas have been generated in a simple magnetron chamber powered with 30-180W at 13.56MHz at pressures ranging from 5-30mTorr. Various H_n⁺, SiH_n⁺, SiH_n fragments (with n = 1, 2, 3) together with Ar⁺ and ArH⁺ species were detected in the discharge. SiH_n fragments, with n =1,2, most significantly affect film deposition, and H fragments most significantly affect the hydrogen.

In a pure argon discharge, the Ar⁺ flux and the deposition rate increases with power.. However, the flux of Ar⁺ decreases as that of ArH⁺ increases with increase hydrogen concentration in the discharge. Plasma parameters, such as plasma potential and electron density and energy, were measured with the Langmuir probe and are in good agreement with the literature. The ion energy of SiH_n⁺ fragments becomes bimodal with increasing hydrogen partial pressure. The roles of possible discharge particle collisions, neutral-neutral, ion-ion, and ion-neutral, and the kinetics leading to the formation of a-S:H are analyzed.

The metastable γ’’’-FeN phase has been discovered a few years ago. This phase crystallizes in the same cfc structure as TiN and CrN. The hard coatings community has not been giving it any interest yet, though it may be possible to create a nanocomposite structure by addition of silicon.

This study aims at depositing adherent γ’’’-FeN thin films – with and without silicon – by PVD on various substrates. The FeSiN coatings were deposited by magnetron co-sputtering of distinct iron and silicon targets. Before this study, attempts to deposit FeN by PVD exposed in the literature resulted either in the synthesis of γ’’-FeN films or of mixed γ’’/ γ’’’-FeN films. By using a higher pressure, thanks to a more important argon flow rate, the deposition of the γ’’’-FeN phase alone was made possible.

The silicon content was adjusted by the variation of the current applied to the Si target. Stress measurements were carried out on coatings deposited on silicon wafers. They confirmed the post-deposition observations of the coatings by showing that their poor adherence to glass substrates was due to very important tensile stress in silicon-free coatings. The introduction of silicon lowers the stress level.

This last phenomenon raises the issue of the localisation of Si atoms in the structure which is discussed here.

We report a new combinatorial approach to study organic thin films. This novel technique consists of in-situ spectroscopic ellipsometry and quartz crystal microbalance methods. In contrast to the quartz crystal microbalance, which is sensitive to the total mass attached to the surface, including the trapped solvent, spectroscopic ellipsometry only measures the amount of adsorbant on the surface. By using these two techniques in tandem, we are able to determine the thickness and water fraction of visco-elastic thin films.

We investigate cetyltrimethylammonium bromide (CTAB) thin films deposited onto a gold-coated quartz crystal as a model system. CTAB grown from a 2.5 mM solution demonstrates several phases in porosity evolution, including a temporary hold in water fraction as the film is rinsed off the substrate with water; these effects may be related to the structure of a CTAB bi-layer.

In addition, a variety of self-assembled monolayers (SAMs) of alkanethiols on gold-coated quartz crystals were used as model biomaterials to determine the water fraction of an adsorbed fibronectin layer. The porosity information was used to distinguish the proteins’ conformation, dictated by the defined surface chemistries of the SAMs. Two protein concentrations in PBS buffer were studied (0.1 mg/mL and 0.01 mg/mL) to isolate how protein concentration affects the above variables.

The Zr₄₃Cu₄₃Ag₇Al₇ system has been developed for a long time for producing bulk metal glass (BMG). The Zr and Cu based BMGs exhibit extremely high glass-forming ability (GFA) and show marvelous properties such as high yield strength, hardness and corrosion resistance, and good thermal and electrical conductivity. Although extensive studies have been performed on BMG, few studies has been reported on metallic glass thin film. In this study, the influence of film thicknesses on the mechanical, electrical properties, residual stress and corrosion behavior are investigated. The ZrCuAgAl metallic thin films with different thickness were deposited on Si and 304 stainless steel substrate in amorphous and crystalline structures by unbalanced magnetron sputtering (UBMS). The color of thin films was silver and the electrical resistivity was quite low. The structure of the ZrCuAgAl films was determined using X-ray diffraction (XRD). The thickness of thin film was obtained by scanning electron microscopy (SEM). The hardness of the film was measured using nanoindentation (NIP). The compositions of the film were obtained by X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the ZrCuAgAl films was evaluated by potentiodynamic scan. The metallic glass thin films had good corrosion resistance in both aerated 0.5 M H₂SO₄ + 0.05 M KSCN solution and 5 wt% NaCl solution. With increasing thickness, the amorphous one had a higher residual stress than crystalline one, using laser curvature measurement.

Transparent conducting oxide(TCO) thin film has been extensively investigated due to its numerous applications in the fields of flat panel displays, organic light emitting diodes, and photovoltaic devices. Indium tin oxide(ITO) thin films have been widely used for the applications because of its low resistivity and high transmittance. However, due to the high cost and the shortage risk of indium raw material, many researchers have explored alternative TCO materials to replace ITO. For the replacement, Ga-doped ZnO(GZO) is regarded as the most promising candidate.

The growth of highly transparent and conductive GZO thin film is possible by sputtering even at room temperature, so that plastic substrate, which might be the essential part of flexible display applications, could also be applicable to the process. For the plastic substrate, polyethylene terephthalate (PET) has been used due to its chemical stability, optical transparency and low cost, comparing to other plastic substrates such as polycarbonate, polyethylene naphthalate, polyehersulfone, and polyimide. However, GZO thin film grown on PET has very inferior damp heat stability due to the poor moisture resistance and high gas permeation of PET substrate. For practical applications of GZO thin film on PET, the damp heat stability is of great importance.

In this study, we report the improved damp heat stability of GZO thin film by pre-treatment of PET substrate. By degassing the PET substrate at high temperature prior to the thin film deposition, we tried to reduce the amount of outgassing moisture and impurity gas, which could deteriorate the electric properties of GZO thin film, during the deposition at the next step. The annealing temperature for the pre-treatment of the PET substrate was 100 ^oC, which is below the glass transition temperature, and the annealing time was controlled by 20, 40 and 60 min. After the pre-treatment, GZO thin films were deposited by rf-magnetron sputtering method using a 5.5wt% Ga₂O₃ doped ZnO target at room temperature. After the deposition, all films were damp heat treated with 90% relative humidity at a temperature of 60 ^oC for up to 150 hr in a climatic chamber. The results of 4-point probe and Hall measurement of the damp heat treated GZO thin film show that the electrical properties could be dramatically improved by pre-treatment of PET substrate. After 150 hr damp heat treatment, the sheet resistance variation of GZO thin film grown on 40 min-annealed PET substrate was about only 15%. The origin of the improvement was investigated by structural, compositional and electrical characterization, and the results will be discussed.

The influence of nitrogen flow on the electrical properties of Silicon-Carbide (SiC) barrier dielectrics prepared by chemical vapor deposition was reported. Experiment results showed that leakage current and dielectric constant was reduced with increasing nitrogen flow. The thermal stability of SiC film was greatly improved by doping nitrogen. The reliability of SiC barrier dielectrics with different nitrogen flows was investigated. An improved dielectric breakdown lifetime was observed due to better Cu barrier ability for nitrogen-incorporated SiC films. In addition, the Cu electromigration performance was slightly enhanced by capping SiC film with higher nitrogen flow because of the improvement bonding strength with Cu.

Precipitates appear on fluorine-doped silicon oxide(SiOF) film when the film surface is exposed to atmospheric air. They are flake-type and hexagonal-shaped and show up rapidly after initiation, and then densely clustered. Energy-dispersive X-ary (EDX) analysis results of the precipitates show that mainly Si & O are detected. From the analysis of Raman spectra, the decreased intensities at about 600 cm^-1 and 500 cm^-1 post precipitation indicates the reduction of strained low-order ring structure in SiOF film. It is found that the dielectric constant of SiOF films initially increases at exposure to air and is attributable to the absorption of water, and then on the contrary a declining trend of the dielectric constant was observed after precipitation. From the Current-Voltage (I-V) characteristics, there is an apparent shift of the breakdown distribution to lower values of electric field for the SiOF films post-precipitation. Slight but appreciable reduction in hardness could be observed along exposure to air and precipitation. Precipitation on SiOF film at exposure to humid air is accompanied by reconstruction in structure, leading to further increase in film porosity and reduction in film rigidity.

The concept of combining the beneficial properties of nanocomposite with those of non-nanocomposite PVD coatings in a single, multifunctional structure has been proven successful for various industrial applications. These triple-coating structures, especially when produced using the cylindrical rotating cathodes technology, provide a balanced mixture of hardness, toughness, abrasional wear resistance, heat barrier and frictional properties. Another advantage is the possibility of depositing a dedicated adhesion layer, thanks to the use of pure elements as the target materials.

The presentation will outline the potential of the triple coating concept based on three examples: Oxygen-containing triple coatings for turning applications, the new superhard TiXCo^® family of coatings for tough hard milling and drilling, and the second generation DLC coatings for components and tools. The influence of different structures on overall coating properties and test performance will be discussed.

The arc ion plating (AIP) technique is known to be capable of providing high film deposition rate and strong film adhesion, while titanium dioxide (TiO₂) is characterized by its high chemical stability, photocatalysis and biocompatibility nature. The present study employed AIP to deposit TiO₂ onto Polyetheretherketone (PEEK) at low temperature. It was aimed to investigate the microstructure, mechanical and electrochemical properties of the TiO₂ coatings as affected by coating variables for its some possible applications . The experimental results indicate that a crystallinic columnar film containing a controllable ratio of anatase to rutile phase can be prepared. Pencil hardness of the PEEK material graded as 4H was increased to over 9H by AIP-TiO₂ coating. Film adhesion of the AIP-TiO₂ coating can ultimately reach a critical load of 15 N and is associated with its deposition condition, but undergoing cohesive failure mode (of the scratch scar) regardless of its deposition condition. Polarization behavior of the TiO₂ coating in 3.5 wt.% NaCl electrolyte reveal that the AIP-TiO₂ coating presents a greater electrochemical inertness, if rutile phase exist. They are however close to the electrochemical behavior of graphite material in all cases.