ICMCTF1998 Session BP: B - Posters
Time Period TuP Sessions | Topic B Sessions | Time Periods | Topics | ICMCTF1998 Schedule
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BP-1 Liquid Movement in the Melt Pool During Laser Alloying or Laser Cladding by Direct Powder Injection Method
M. Bamberger, W.D. Kaplan, B.S. Medres, L.B. Shepelev, M. Riabkina-Fishman (TECHNION-Israel Institute of Technology, Israel) Mechanism of liquid stirring in the melt pool formed by a CW-CO2-laser beam in the process of obtaining surface coating by laser surface alloying (LSA) and laser cladding (LC) has been studied. It was been shown that in the case of direct injection method (DIM) the pressure exerted from the surface of the melt pool by the transporting gas flow and by injected particles by two order of magnitude higher than the forces of surface tension that govern the movement of liquid in the melt pool formed by laser melting of predeposited coatings. Velocities of liquid movement in the melt pool have been also evaluated. It has been shown that proposed mechanism of liquid movement results in multiple stirring of the melt that account for the observed chemical and structural uniformity of LSA and LC coatings.In the case of a deep melt pool, when its depth is equal to or higher its effective radius, liquid moves only in the plane of laser beam scanning. Metallographic and SEM observations well correlating with the proposed mechanism of LSA and LC coatings formation by DIM are presented. |
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BP-2 Improvements of Mechanical Properties of Ti-based Multilayer PACVD Coatings on Tappets of a Diesel Engine
M.-J. Lee, Y.K. Kim, H.S. Kim, H.Y. Song, K.H. Lee (Institute for Advanced Engineering, Korea) Recently it has become a critical issue to improve the wear resistance of tappets in a diesel engine as their performance requirements are getting higher. To deal with this problem, several Ti-based multilayer coatings have been deposited on the tappets using a pulsed dc PACVD process. Titanium-based coatings are commonly applied on steels because of the excellent inherent properties. In this expriment [TiN-TiC]n multilayers were obtained to investigate the mechanical characteristics such as stress, wear resistance, friction and other properties. The multilayers were obtained by periodic interruptions of the nitrogen flow or methane flow to produce alternating layers of titanium-titanium nitride or titanium-titanium carbide. The results are presented and compared with each other as well as with the single layers of TiN and TiC. Improvements of mechanical properties of Ti-based multilayer coatings on tappets will be discussed. |
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BP-3 Mechanical and Electrical Properties of Diamond-like Nano-composite Thin Films
D.J. Kester, C. Venkatraman, C.A. Outten, D.J. Bray (Advanced Refractory Technologies, Inc.) Diamond-like Nanocomposites (DLN) are a family of amorphous thin film coatings containing C, H, Si, and O. In addition, metal atoms may be incorporated into the coatings. The coatings have the mechanical properties of low wear, high hardness, low friction, low stress, and good adhesion to a variety of substrates. Hardness and elastic modulus values were measured using nano-indentation, and ranged from 5 - 30 GPa for hardness and 50 - 300 GPa for modulus. Film stress was significantly lower than that of diamond-like carbon (DLC) films of equivalent hardness, with typical stress values of 200-1000 MPa. Wear and friction were measured using a ball-on-disk tribometer. Wear factors as low as 3 x 10-8 mm3/Nm were measured. The coefficient of friction ranged from 0.01 to 0.2. The electrical resistivity may be varied over 15 orders of magnitude, from 1014 to10-1 ohm-cm. The dielectric strength of undoped DLN has been measured as high as 2.53 MV/cm. |
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BP-4 Investigation of Alternative TiN Layers Produced by Balanced and Unbalanced Magnetron System
R. Beloseva@aa c@, A. Kunosi@aa c@, M. Zlatanovi@aa c@ (Faculty of Electrical Engineering, Yugoslavia); N. Popovic (Institute of Nucelar Sciences Vinca, Belgrade, Yugoslavia) Magnetron sputter ion plating system was used for multilayer hard coating deposition onto HSS substrates. The influence of magnetron discharge properties on hard coatings behavior was investigated by varying an external magnetic field configuration. Additional deposition process control was performed by an auxiliary anode. Substrates were treated alternatively in balanced and unbalanced mode. The dependence of coating structure, morphology, topograohy, microhardness and deposition rate on substrate material and deposition coditions was investigated by several characterization techniques. Microhardness and adhesion measurements, SEM, XRD and metalographic analyses were employed to study the magnetic field influence on depositited coating properties. The scratch test equipment was also used for testing the abrasive wear properties of multilayer coatings. |
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BP-5 Some Optical , Mechanical and Structural Characteristics of Magnetron Sputtered TiNx Films
M. Zlatanovi@aa c@, D. Djuki@aa c@, D. Sesum (Faculty of Electrical Engineering, Yugoslavia); N. Popovic (Institute of Nucelar Sciences Vinca, Belgrade, Yugoslavia) The variation of reflectivity, index of refraction, real and imaginary part of dielectric function, absorption coefficient and CIE l*a*b* chromatic coordinates of TiNx coatings due to variation of deposition parameters was investigated. The double and single balanced magnetron depostion system were used in experiments. Reflectivity and ellipsometry measurements, scratch test, calotest and microhardness measurements, as well as STM, SEM and XRD analyses were performed. The coatings deposited in double magnetron configuration show significant changes of optical, mechanical and structural characteristics due to small variation in nitrogen flow at other parameters kept constant. The reflectance curve was found "sensitive" to small variation of nitrogen flow during deposition process. The position of reflectance minimum on the wavelength scale and its value, as well as the overall shape of reflectance curve of TiN coating depend on nitrogen flow during film growth. In the case of single balanced magnetron, optical and structural characteristics of deposited TiNx coatings depend on target to substrate distance. In this case the optical characteristics change during time, which was not the case with the double magnetron deposited samples. In all cases the mechanical characteristics of the coatings were stable during aging. The correlation that exists between some optical and mechanical characteristics of TiNx coatings may be used to estimate mechanical and structural coating properties only during a limitted time period after deposition |
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BP-6 Sputter Deposition of TiN Thin Films Using Optical Emission Spectroscopy (OES) as Process Monitor
F. Sequeda, G. Zambrano, P. Prieto (Universidad del Valle, Colombia); C. Rincon (Universidad Autonoma de Occidente, Colombia); N. Alba (Universidad del Valle, Colombia) TiN films were deposited onto various substrates by magnetron sputtering in a N2/Ar gas mixtures at differents temperatures. The power, the ratio of gas flows and the total pressure were systematically varied. To optimize the deposition conditions, the plasma excitación processes were examined by Optical Emission Spectroscopy (OES). In the range of pressures investigated, the deposition rate is linearly proportional to the intensity of the optical emission at 364.2 nm, I (Ti), associated with excited Ti. The N/Ti ratio in the deposited films, as determined by Rutherford Backscattering and ESCA, is found to be linearly correlated with the ratio of the optical emission intensities of excited N+ 2 (391.4 nm) and Ti at 364.2 nm, I (N+ 2)/I (Ti). This works shows the possibility to deposit stoichiometric TiN films by controlling the deposition process using the information provided by in-situ OES. |
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BP-7 Ion Implantation Inducing Modifications on Polymer Films Deposited by Plasma-Enhanced CVD
E.C. Rangel, N.C. Cruz, L.C. Kretly (State University of Campinas, Brazil); C.M. Lepienski (Federal University of Parana, Brazil); M.A.B. de Moraes (State University of Campinas, Brazil) Exposition of a polymer to an energetic ion beam can induce, amongst other effects, crosslinking and degradation of the chains and formation of unsaturated carbon bonds. Differently of the degradation, the high degree of crosslinking produces a thermically stable, hard and resistant to chemical attack and mechanical wear material. This work describes the influence of the current, the dose and the ionic species used in the beam on the properties of plasma deposited polymers. The films were produced by PECVD from rf (40 MHz, 70W) plasmas of C6H6 and O2 mistures. Afterwards, they were implanted with He, N and Ar ions at 150 keV. The dose was fixed at 10 16cm-2 and the current ranged from 0 to 400 μA. Hardness studies were carried out using Ar ions at 150 keV and varying the dose from 10 13 to 10 17cm-2. Structural and optical properties were analyzed by infrared (IR) and ultraviolet-visible spectrtoscopies, repectively. A two-point probe was used for determination of the electrical resistivity. The chemical resistance was evaluated from the etching rate of the films by an oxygen rf plasma. The molecular structure of the samples was affected by the implantation and a strong dehydrogenation was observed from the lack of C-H bond absorptions in the IR spectra. The optimum implantation conditions produced a drop of five times in the etching rate compared to the as-deposited film. Both the optical transmittance and electrical resistivity of the polymers decreaed after irradiation. These effects are likely associated with the increase in the density of delocalized π-electrons from the unsaturated bonds generated by the ion bombardment. A model connecting the ion energy-loss mechanisms and the variations in film properties is proposed. |
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BP-8 ECR Oxygen-Plasma-Assisted Growth of Hard Zirconia Films on Sapphire
S.C. Moulzolf, R.J. Lad (University of Maine) Zirconia is used as a hard coating for such applications as recording media and gas turbines. Films for such applications are typically doped with compounds such as yttria and magnesia to stabilize the high temperature bulk equilibrium phases of zirconia. Using electron cyclotron resonance (ECR) oxygen-plasma-assisted electron beam evaporation of Zr, we have been able to synthesize amorphous, polycrystalline, and epitaxial films on sapphire containing varying amounts of the cubic and monoclinic zirconia phase with and without yttria dopant. For films less than 40 nm thick on both c-cut and r-cut sapphire, in situ RHEED indicates that single phase cubic zirconia can be grown for certain deposition parameters without the addition of a stabilizing dopant due to lattice matching with the sapphire substrate. At higher film thickness, coexisting monoclinic and cubic phases are present. On r-cut sapphire, polycrystalline zirconia films with nanometer-sized grains are formed at deposition temperatures below 300°C whereas highly textured films are produced above 475°C. On c-cut (basal) sapphire, heat treatments can lead to surface reconstruction of the bare substrate, and this in turn dictates the exact film microstructure. Films containing a larger fraction of the cubic phase exhibit lower friction and wear in pin-on-disk tests. Continuous indentation results with a Hysitron pico-indenter show that the hardness is directly correlated with film microstructure. |
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BP-9 Laser Fluence Effect on the Formation of Dielectric PLT Thin Films
D.S. Eun, J.H. Park, C.Y. Park, S.Y. Lee (Yonsei University, Korea) Dielectric thin films of PLT (28) (Pb0.72La0.28Ti0.93O3) have been deposited on Pt/Ti/SiO2/Si substrates in situ by a laser ablation. We have systematically investigated the effects of the laser energy density. The laser energy density has been varied from 1 J/cm2 - 5 J/cm2. The surface morphology and the crystal structures of the thin films have been observed to strongly depend on the laser energy density by scanning electron microscopy (SEM) and X-ray diffraction method (XRD). The composition of the thin films has been observed to be varied depending on the laser energy density. The electrical measurement indicated that laser ablated PLT thin film showed high dielectric constant of about 1400. |
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BP-10 A Study on the Pulsed Laser Deposition of Diamond Like Carbon Thin Films
S.Y. Lee, Y.S. Jeong, D.S. Eun, H.S. Jung (Yonsei University, Korea) Pulsed laser deposition (PLD) can be utilized to generate films with desired properties quite different from those of the starting material. Since diamond-like carbon (DLC) films grown by PLD using turbo pump are perpared without hydrogenated DLC films. In general, the degree of diamond-like character mainly estimated by the fraction of sp3 hybridized carbon bonding in a film varies considerably with the deposition parameters. In this study, effects of the substrate temperature, laser energy density, and laser wavelength on the properties of DLC films have been studied by scanning electron microscopy (SEM), X-ray diffraction, Raman spectroscopy, electron energy loss spectroscopy (EELS), electrical conductivity and optical measurements. By varying the deposition temperatures and the laser energy densities from room temperature to 600°C and from 6 to 17 J/cm2, respectively, the optimized deposition condition for DLC films has been obtained. The deposition condition of DLC films was optimized at the laser energy density of 12 J/cm2 and at the substrate temperature of 300°C, while graphitic films were fabricated at the substrate temperature of 200°C. This optimized deposition condition will contribute the fabrication of high quality DLC films for the use of electron field emission cathodes. |
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BP-11 Microstructural Characterization of a VC Laser Cladding Coatings
Y. Herrera (Central University of Venezuela, Venezuela); I.C. Girgorescu (INTEVEP S.A., Venezuela); M.H. Staia (Central University of Venezuela, Venezuela) The present investigation describes the results of laser cladding VC coatings on 1045 AISI steel produced by using Nd: YAG laser. Microstructural characgerization was performed on the polished cross section samples previously etched by using Vilella etchant. The microstructure and composition of the coatings were studied by using optical microscopy, scanning electron microscopy (SEM) coupled with dispersive energy X- ray analysis (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Microhardness measurements of the coatings were performed on both cross section and surface of the samples. Three main phases were identified: V8C7, VC with a variable content of iron bounded by a matrix composed mainly of Fe which contains dissovled Mn, C and V. Fe3C dendrites were identified at the interface coating substrate. Image analyzer was used in order to determine the particle size and distribution of the vanadium carbide particles across the coating. |
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BP-12 Microstructural Characterisation of Laser Induced Pulsed Arc Deposited Carbon Films and Multilayers
J.-J. Scheibe, A. Luft, J. Kaspar, H. Ziegele (Fraunhofer Institut für Werkstoff und Strahltechnik, Germany) Sinlel and multilayer films consisting of titanium or aluminum and amorphous carbon were deposited on silicon by the laser induced pulsed arc technique (Laser-Arc). The amorphous carbon has a hardness in the range between 40-60 Gpa and a high elastic modulus (400 - 600 Gpa). In comparision to similar hard C-films prepared by other techniques these films show low internal stress (< 2 Gpa). By combination of carbon films with thin metallic interlayers (Ti or Al) the film thickness can be increased up to some microns. A JEM 2010 Tem with EDX was used to study the cross section micromorphology and -structure of these single and multilayered films. In contrast to the amorphous carbon the metallic interlayers are crystalline. Beside small metallic particle inclusion some artifacts in the microstructure of the amorphous carbon are found and discussed in connection to the deposition conditions. |
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BP-13 Fabrication and Characterization of Double-sided YBCO Superconducting Thin Films Using Laser Ablation
J.H. Park, Y.S. Jeong, S.Y. Lee (Yonsei University, KOREA) Epitaxial growth of double-sided high-Tc superconducting(HTSC) thin film has been systematically investigated since it is important for microwave applications as well as for fundamental researches. We have fabricated highly c-axis oriented YBa2Cu3O7-x(YBCO) superconducting thin films on (100) MgO substrates by pulsed laser deposition(PLD). In particular, devices like microwave stripline filters for communication systems require high quality HTSC thin films on both sides of single crystal wafers. To use one-side film as a low loss ground plane, we have used halogen lamp to heat up the substrate without silverpaste to preserve its backside for the fabrication of double-sided superconducting thin films. Also, we have observed the film orientation has been changed from c-axis to a-axis as increasing the film thickness by X-ray diffraction. This should be considered for the application of superconducting microwave devices. By optimizing the thickness and the deposition temperature of YBCO thin films, highly c-axis oriented double-sided YBCO thin films have been fabricated. The transition temperature of these films has shown to be about 88K. |
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BP-14 Large Area Pulsed Laser Deposition of High Quality Multilayers
Th. Holz, R. Dietsch, H. Mai (Fraunhofer Institute Material and Beam Technology, Germany); H. Scheibe (Fraunhofer Institute Material and Beam Technology) Pulsed Laser Deposition is used for the preparation of high quality metal/carbon, carbon/carbon and metal/metal multilayers having period thicknesses in the nm-range. To realize high quality multilayer stacks on large areas a double-beam PLD-source was integrated into a commercial MBE system. Layer stack morphology, interface roughness and reproducibility of period thickness in the total stack were characterized by means of high resolution transmission electron microscopy, secondary neutral mass spectrometry and X-ray reflectometry to demonstrate precision and reproducibility of the coating process. Selected multilayer applications in X-ray optics are demonstrated. For graded Ni/C-multilayers consisting of up to 75 double layers with period thicknesses between 3.0 nm and 5.5 nm thickness gradients in the range 0.1 - 1.0 nm/cm across the total substrate length are realized. Grazing incidence reflectivity of up to 85% and an excellent energy resolution are obtained. |
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BP-15 Nitrogen Transport During Ion Nitriding of Austenitic Stainless Steel - the Role of the Native Surface Oxide Layer
S. Parascandola, O. Kruse, R. Günzel, E. Richter, W. Möller (Forschungzentrum Rossendorf, Germany) Austenitic stainless steesl are widely used due to their advantageous combination of properties as ductility, strength and excellent corrosion resistance However, due to their moderate hardness they are not suited for abrasively stressed parts. Hence, the market potential of austenitic stainless steels could be greatly enhanced by a technique allowing surface hardening without adversely affecting the corrosion resistance. While techniques as heat treatment, carburizing and gas nitriding fail, plasma ion nitriding is a promising candidate. At moderate temperatures (about 400 °C) the formation of a layer which is characterised by a high content (about 20at.%) of nitrogen in solid solution is well established. Layer thickness up to some tens of μmm and significantly improved hardness and wear and excellent corrosion resistance have been observed. Normally nitriding can be described in good approximation as diffusion into a semi-infinite solid during constant surface concentration. However, during plasma ion nitriding austenitic stainless steel at moderate temperatures fast nitrogen diffusion and unusual nitrogen concentration profiles have been observed. Additionally, a native surface oxide layer is supposed to act as a diffusion barrier. It has been reported that for constant temperatures the nitriding velocity increases with either current density and ion energy. This gives rise to assume that for high nitriding velocities the surface oxide layer has to be removed by sputtering or that the ion energy and the corresponding ballistic implantation depth has to be sufficient to overcome the barrier. paragarph Since the nitrogen retention is supposed to be affected by the surface oxide layer and therefore by ion implantation, sputtering and re-oxidation from the residual gas a dynamic in-situ ion beam analysis experiment using a crossed beam geometry was set up. Plasma ion nitriding is performed using a Kaufman-type broad-beam ion source. Dynamic depth resolved compositional analysis is performed by elastic recoil detection analysis using a 35MeV chlorine ion beam. Elastic recoil detection analysis is sensitive to light elements as carbon, nitrogen and oxygen and has been optimized regarding fast data acquisition here. Additionally the residual gas is controlled by a quadrupole mass analyzer and a variable gas inlet. Preliminary results have shown that the nitrogen retention is strongly correlated with the reduction of the surface oxide layer. Quantitative time resolved measurements of the nitrogen concentration profiles will be presented for various oxygen partial pressures, nitrogen ion energies and current densities. The results will be compared with theoretical predictions of the adsorption rate from the residual gas, the ballistic implantation depth and the sputtering rate. The aim is to develop a quantitative transport scenery for plasma ion nitriding austenitic stainless steels at moderate temperatures with emphasis on the role of the surface oxide layer. |
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BP-16 Nitriding of Silicon by Using ECR Nitrogen Plasma
T. Hino, M. Harada, Y. Hirohata (Hokkaido University, Japan) Nitriding of silicon was conducted by using an ECR nitrogen plasma. The effects of dischrge pressure, substrate temperature and the bias voltage of substrate on the nitriding were investigated. The nitriding was enhanced by the increase of nitrogen ion energy, which was adjusted by the bias voltage, under the low pressure discharge. The nitriding was also enhanced with the substrate temperature higher than approximately 500 °C. The amount of retained nitrogen in silicon was observed to saturate for the nitrogen fluence more than 1018 N/cm2. The maximum nitrogen concentration observed in the present experiment was 40 at.%. The formation of Si-N bond in the implanted region was also observed. |
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BP-17 The Influence of Magnetron Configuration on Ion Current Density and Deposition Rate in a Dual Unbalanced Magnetron Sputtering System
P. Kelly, R.D. Arnell (University of Salford, United Kingdom) A series of experiments were carried out to investigate the influence of magnetron configuration on the performance of a dual unbalanced magnetron system. The rig was operated in the closed-field (CF), mirrored-field (MF) and, for comparison, single unbalanced magnetron (UBMS) configurations. The performance of the rig was assessed in terms of the substrate ion current density, Is, deposition rate, R, and the ion-to-atom ratio incident at the substrate, Ji/Ja. R was not significantly influenced by magnetron configuration. Also, for all configurations, R decreased with increasing substrate-to-target separation, ds-t, in a relationship of the form R = a(ds-t)b, where b approximately equals -2. Is also decreased with increasing ds-t. However, Is values were 2-3 times lower, and the rate of decrease of Is was greater, when operating in the MF, or UBMS modes, compared to the CF mode. Values of b in the relationship Is = a(ds-t)b were -0.26, -0.53 and -0.58 for the CF, UBMS and MF modes, respectively. An important finding of this study is that, although both deposition rate and ion current density decrease with increasing separation, because the rate of change with separation is different in each case, the ion-to-atom ratio actually increases with increasing separation. For example, operating in the CF mode, Ji/Ja was found to increase from 1.25 to 3.0 when ds-t was increased from 80mm to 150mm. |
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BP-18 Hardness and Morphological Characterization of Tungsten Carbide Thin Films
P. Prieto Pulido, G. Zambrano, F. Perez (Universidad del Valle, Colombia); C. Rincon (Universidad Autonoma de Occidente, Colombia); H. Galindo (Universidad de los Andes, Venezuela); L. Cota-Araiza (IFUNAM, Mexico); J. Esteve (Universidad de Barcelona, España) We have prepared Tungsten Carbide thin films (WC+Ni) onto stainless steel (AISI 316L) and WC substrates by a non-reactive d.c. magnetron sputtering process from sintered WC target with 6 wt % Ni. The WC+Ni hard coating films with thicknesses between 0.5 and 4 Μm have been deposited at temperatures between 300 C and 500 C. The structure of the films were characterized using X-ray Difraction Spectroscopy (XDR), Auger Electron Microscopy (AES) and Reflection Absorption Infrared Spectroscopy (RAIRS). The morphological analysis was carried out using Atomic Force Microscopy (AFM) and the microhardness was measured by the dinamical nanoindentation method. AES and RAIRS results confirm that the carburization process depend on the substrate temperature. AFM analysis indicated that the growth mechanism of the films is of columnar type. The microhardness measurements showed that coatings with large hardness values can be prepared at a relative low temperature. Films obtained by this way have small grain size and low C concentration. |
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BP-19 Deposition of High Quality TiAlN Hard Coatings by Vacuum Arc Deposition Process
D.Y. Wang, Y.W. Li (National Chung Hsing University, Taiwan, ROC); N.H. Wang, W.Y. Ho, J. Chang (Surftech Corp., Taiwan, ROC) TiAlN demonstrated significant improvement in hardness, toughness, and heat resistance over conventional binary metal nitrides. Due to the differences in melting temperatures and sputter yields between Ti and Al, TiAlN was best deposited by the vacuum arc deposition process for cutting applications. However, the prevented problem of macrodroplets TiAlN hard coatings from applications requiring stringent surf ace finish. In this study, the filtered arc technique combined with a plasma enhanced mechanism was adopted to deposit high quality TiAlN hard coatings. Extended ion bombardment at under variable biasing voltage showed significant effects in stress reduction and resulted in improved film adhesion. For both high-speed steel and WC/Co substrates, the as-deposited TiAlN outperformed TiN in milling and drilling tests. The bias control remained an effective means to reduce the cathode spits and the substrate re-sputtering of aluminum. The fewer and smaller remaining macrodroplets were filtered out effectively. High quality TiAlN of was obtained. The microstructure and chemical analysis were conducted by XRD, EPMA, and SEM. The tribological properties of TiAlN was discussed in terms of the deposition parameters. |
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BP-20 Opto-electronic Properties of Amorphous Silicon Films Rapidly Grown by Filtered Vacuum Arc
D. Arbilly (Tel-Aviv University, Israel); R. Naidis, I. Balberg (Hebrew University, Israel); R.L. Boxman (Tel Aviv University, Israel); S. Goldsmith (Tel-Aviv University, Israel) A Si plasma beam was generated by a vacuum arc sustained on a heated intrinsic Si cathode, and passed through a quarter-torus macroparticle filter. The films were deposited on fused-silica glass substrates at temperatures of 250-450 °C. A rate of deposition around 100 Å/s was achieved. Hydrogen gas was introduced into the deposition system near the cathode during the film growth. The minority carrier diffusion length was measured using the photo-carrier grating (PCG) method. In addition the Raman spectra and the film dark conductivity and the photo-conductivity were measured. The Raman spectra on samples deposited without hydrogen revealed a peak at 460 cm-1, with a line width of 125 cm-1. Preliminary results with hydrogenated samples indicated that the ratio between the photo and dark conductivities was several hundreds and the minority carrier diffusion length was up to 500 Å. The deposition parameters were optimized by searching for suitable combinations of film substrate temperature and background hydrogen gas pressure. |
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BP-21 Growth of GaN Films by Reactive Sputtering of GaAs
N.M. Elkashef, N.A. Preschilla, R.S. Srinivasa, S. Major (Indian Institute of Technology, Bombay, India) Deposition of gallium nitride films by reactive sputtering of metallic gallium target is known to face practical difficulties arising due to the low melting point of gallium and the formation of gallium nitride scum on the target surface, which warrants prolonged presputtering and is known to result in poor reproducibility of the films. Here, we report the use of GaAs as an alternative target material for the sputter deposition of GaN films. The films were grown at different compositions of the sputtering gas mixture ( 0 - 100 % nitrogen in argon), substrate temperatures ( 700K - 900K ) and rf power. While the films deposited in 100 % argon were of GaAs, introduction of about 10 % nitrogen in the sputtering medium was found to prevent the formation of GaAs. The films grown in argon - nitrogen mixtures ( >10 % nitrogen ) at lower temperatures consisted of GaN crystallites in an amorphous matrix. In contrast, the films grown at higher substrate temperatures showed only hexagonal GaN with improved crystallinity. Most interestingly, the films grown with 100 % nitrogen in a wide range of rf powers and temperatures were found to be polycrystalline, single phase, (0002) oriented GaN. XPS studies revealed complete absence of arsenic and metallic gallium and confirmed the presence of GaN. This is the first time GaN films have been grown using a GaAs target. GaN could be grown using 100 % nitrogen as the sputtering cum reactive gas without target poisoning effects. Possibly, this is the first instance where a nitride film has been formed by nitrogen sputtering of a different compound. |
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BP-22 Corrosion Protection of AISI 304 Austenitic Steel by Y, and Er by Ion Implantation Against Isothermal and Cyclic Oxidation
F.J. Perez, E. Otero (Universidad Complutense de Madrid, Spain); M.P. Hierro (Universidad Complutense de Madrid, Spain); C. Gomez, J. Cristobal, G. Arnau (Universidad Complutense de Madrid, Spain) To improve the high temperature corrosion behaviour of different materials different Y and Er have been implanted into the surface of AISI 304 austenitic steel. Isothermal and cyclic oxidation kinetics experiments have been established up to 500 hours of test. The implanted surface and corrosion products formed on the surface have been analysed by Auger Electron Spectroscopy (AES), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), and X-Ray diffraction patterns. Theoretical calculations have been performed in order to achieve the best deep profile in order to indentify the surface damage during the implantation process. A protection mechanism according to the results obtained in both oxidizing conditions tested is proposed. |
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BP-23 Ultra Hard Ti-B-N Coatings Obtained by Reactive Magnetron Sputtering of a Ti-B Target
C. Heau (Hydromecanique et Frottement Group, France); J.P. Terrat (Hydromécanique Et Frottement Group, France); Ph. Maurin-Perrier (Hydroécanique et Frottement, France) The influence of the chemical composition of TiBN compounds on their properties has been studied using reactive cathodic magnetron cosputtering from a Ti and a TiB2 target. The wide explored zone (0 to 60% N and 0 to 60% B) has shown two ultra hard regions, one with high B and low N content and the other one with medium B and N content. Abrasive wear tests in water have also shown very high wear resistance for the coating with medium B and N content. From these results, a B containing Ti target has been elaborated in order to obtain the B/Ti ratio corresponding to the high abrasive wear resistant coating. Deposition rate has been studied as a function of N2 flow. Variations of deposition rate have been correlated with cristalline structure transition which shows an unidentified phase for N2 flow comprised between 0 and 5 sccm. The chemical composition indicates that this phase could be Ti2B for N2 flow comprised between 6 and 8 sccm, coatings have fcc structure which lattice parameter decreases when N2 flow increases. Coatings obtained at N2 flow over 8 sccm are constituted of a mixture of TiN and tBN. Scratch test measurements indicate good adhesion of the 10 μm thick coatings on the C35E steel. The hardness increases from 10 to 45 Gpa when N2 flow increases from 0 to 5 sccm and then remains constant. The abrasive wear test has shown the maximum resistance of coatings for 6 sccm N2 flow. The wear resistance of this TiBN coating is 3 times better than the one of TiN or CrN. Results obtained from a single B containing target are in good agreement with those obtained using reactive magnetron cosputtering. The coating containing 55% Ti, 19% B and 26% N shows high hardness 45 Gpa) and excellent abrasive wear resistance. |