Papers

ICMCTF1998 Session B5: Ion-Assisted Deposition and Ion Beam Technologies

Friday, May 1, 1998 8:30 AM in Room California

Friday Morning

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8:30 AM		B5-1 High IntensePulsed Ion-beam Sources and their Industrial Application G.E. Remnev, I.F. Isakov, M.S. Opekunov, V.M. Matrienko, V.K. Struts, I.I. Grushin, A.N. Zakoutayev, A.N. Potyomkin, A.N. Pushkaryov (Tomsk Polytechnic University, Russia); M.Yu. Ovchinnikov, V.L. Kutuzov (Scientific Industrial Enterprise LINETRON, Inc., Russia) The report describes sources of high power pulsed ion beams, used for applied researches in material science (e_U=100-300 keV, j_i=1-250 A/cm², t_p=50-200 ns). Accelerators "TEMP" have a mixed beam, consisted of carbon ions and protons; the modification of treated materials is based on short-pulsed thermal influence to surface layers of these materials. A short-pulse implanter "MUK" has pulse repetition rate up to 10 Hz; it can generate beams, consisted of metal and dielectric ions. Both implantation and thermal inluence, providing defect annealing, can be achieved on the implanter. The report describes results of practical application of the "TEMP-4" accelerator for hardening of cutting tools. Possibilities of application of high power ion beams for producing of metal and alloy films due to spattering of corresponding targets are discussed.
9:10 AM		B5-3 Carbon, Nitrogen and Oxygen Implantation Into TiN Coatings F. SEIDEL (Institut für Werkstofftechnik (IWT), Germany); H.-R. Stock, P. Mayr (Institut f für Werkstofftechnik (IWT), Germany) TiN coatings are widely used in industry especially for forming and cutting tools. Ion implantation is a very promising possibility for further improvement of the wear behaviour of the coatings. Increased surface hardness and reduced wear and friction can be realised, but ion beam treatments can lead to reduced hardness, too. The reasons for the high efficiency of ion implantation in some cases and less successful application in others are not well understood. Therefore in this investigation metallographic and chemical analyses of implanted layers are presented to explain the different changes of the mechanical coating properties. Polished high speed steel samples were first coated with TiN by magnetron sputtering and then implanted with N⁺, C⁺ and O⁺ at ion energies of 180 keV and doses between 0.5 and 6x10¹⁷ cm^-2. Colour changes in the TiN coating due to the ion implantation were observed and spherical sections were fond to be a suitable metallographic method for investigation of radiation effects. With this techniques it is possible to visualize ion- and dose-dependent changes within the about 0.5 µm thick implanted zones. Morphology of carbon implanted TiN show a depth dependent colouring which is in coincidence with the theoretical prediction of the implantation depth profile. Nitrogen implantation, especially in higher doses, lead in contrast to carbon implantation to uniform dark layers. Chemical analyses of the implanted layers were carried out using GDOS and XPS analyses. Good correlation between chemical composition and results from the metallographic investigations were found. Precipitation of non-carbidic carbon were detected after high-dose carbon implantation, a saturation limit for nitrogen was found for high-dose nitrogen implantation. Nanoindentation measurements reveal different changes in surface hardness depending on ion species and ion dose. Significant increases of the hardness values are found after carbon and oxygen implantation in relatively low ion doses. The correlation between the changes in hardness and the results of metallographic and chemical analyses are discussed.
9:30 AM		B5-4 Processing of Metals by Plasma Immersion Ion Implantation for Improved Mechanical Properties W. Ensinger (Universitat Augsburg, Germany); M. Rinner, K. Volz, B. Rauschenbach (University of Augsburg, Germany) Plasma immersion ion implantation PII has been developed a decade ago for modifying mechanical and chemical surface properties of metals. In analogy to conventional beam-line ion implantation, it uses energetic ions, mostly nitrogen, which are implanted in the near-surface region of a material. The present paper discusses the influence of the PII process parameters ion density, pulse repetition rate, and sample temperature on hardness and wear resistance of stainless steel and a titanium-alloy and correlates these properties with compositional and structural features. The results show that nitrogen ion implantation leads to an increase in hardness combined with a reduction in the wear rate. Whereas in case of steel a medium process temperature (600-700 K) yields a surface hardening which extends to depths in the micron range due to nitrogen diffusion, in case of titanium the modified zone remains shallow. Nevertheless, the wear performance is improved. Phase analysis shows that in case of stainless steel the expanded austenite phase is formed, whereas for titanium a thin surface layer of TiN is formed.
9:50 AM		B5-5 Formation of Hard Coatings for Tribological and Corrosion Protection by Dynamic Ion Mixing J.P. Riviere (University of Poitiers, France) In recent years there has been new developments in coating technologies involving the use of ion beams. Ion implantation and ion beam mixing of predeposited layers have proved to be powerful and versatile tools for producing surface alloys. However the potential applications are limited by their shallow depth of treatment (submicron order). By combining physical vapor deposition (PVD) and ion implantation, the dynamic ion mixing (DIM) technique removes the thickness limitation imposed by finite ion ranges Rp allowing to produce thicker coatings and preserves the advantages of both individual processes. The bombardment of a growing film with energetic ions (i.e. 100-400keV) results in beneficial changes such as : improved adhesion, increased densification as well as controlled structure and phase formation .Thus DIM can be considered as to have distinct advantages for producing dense and adherent ceramic coatings at room temperature. One of the most important feature of this technique is to induce atomic mixing of the coating with the substrate in the initial stage of deposition (i.e. when the film thickness is less than Rp ). This spatial redistribution of atoms at the coating/substrate interface is produced at room temperature by ballistic effects and results in a broad interface of graded composition. When the deposited thickness exeeds Rp, the atomic displacements and replacements occur in the coating allowing to control phase formation and densification. In general, a heavy ion beam of inert element is used for mixing(i.e. Ar, Kr, Xe) and vapor sources are either ion beam sputtering or electron beam evaporation. Typical experimental results obtained with different hard coatings : TiB2, TiC, TiNi(N) and SiC will be presented. For all these coatings the enhancement of crystallization, densification, wear and corrosion resistance was observed. Interesting tribological properties were obtained for nanocomposite coatings formed of fine precipitates of hard TiN phase embedded in a ductile NiN3 matrix. The improved properties of DIM coatings are dicussed and analyzed in relation with collisional effects induced by the high energy ion bombardment.
10:30 AM		B5-7 Deposition of Metal Nitrides by IBAD T. Sikola, J. Spousta, R. Ceska, J. Zlamal, L. Dittrichova (Technical University of Brno, Czech Republic); A. Nebojsa, K. Navratil (Masaryk University Brno, Czech Republic); R. Kuzel (Charles University Prague, Czech Republic); V. Perina (Academy of Sciences of the Czech Republic) Nitrides of metallic elements like Ti, Zr, Mo and Al were synthesized by ion beam assisted deposition (IBAD). This technique was provided via dual ion beam deposition method in an apparatus designed in our group. The apparatus consisted of two Kaufman ion beam sources. The primary source with a grid diameter of 150 mm was used for sputtering of metallic targets, the secondary source with a 75mm-grid diameter was applied for the concurrent bombardment of growing films by nitrogen ions. In our study the influence of the 100 - 400 eV assisting ion beams and the substrate temperature (up to 400 degrees) on the characteristics and properties of deposited thin films (chemical composition, structure, roughness, thickness, optical and electrical properties etc. ) was investigated. Different ex-situ analytical techniques and measurements such as RBS, NRA, XPS, XRD, STM/SFM, profilometry, ellipsometry and other methods were used. The composition of thin films prepared by the sputtering of Ti was close to oxinitrides for all ion energies (fluxes). The oxygen content in the other thin films was substantially lower. The nitr ogen content in all films grew with ion energy (flux), however, it sustained under their stoichiometric values. Structure of all thin films was, as a rule, X-ray amorphous. The roughness and thicknes s (50 - 400 nm) of the films increased, respectively decreased with ion energy (flux). Higher substrate temperature (400 degrees) substantially improved the adhesion of MoN films to silicon substrate s. A remarkable improvement of MoN adhesion to Si substrates due to the bombardment by ions of higher energies (200 - 300 eV) was also observed. The index of refraction of thin films varied with ion energies (fluxes) in a complex way. A significant influence of the assisting ion beam on resistivity of TiN and AlN was observed. The resistivity of TiN and AlN films went down (to 10⁰ ohm), respectively up (to 10⁶ ohm) with ion energy (flux).
10:50 AM		B5-8 Non-Uniform SiO₂ Membranes Produced by Ion Beam Assisted Chemical Vapor Deposition To Tune WO₃ Gas Sensor Microarrays J. Goschnick, M. Frietsch, T. Schneider (Forschungszentrum Karlsruhe GmbH, Germany) Gas sensor high volume applications, e.g. for car climate or exhaust control, or home food processing, stimulated the development of a gas sensor microarray of thumbnail size based on the gas-sensitive electrical conductivity of semiconducting metal oxide thin layers. The array of 40 sensor elements is simply constructed by partitioning a rectangular metal oxide layer with strips of parallel electrodes. Each metal oxide segment with its two adjacent electrodes forms one sensor element initially identical to the neighboring elements. However, in the final production stage the array of metal oxide gas detectors is coated by chemical vapor deposition with an inhomogeneous SiO₂ layer, thin enough to be highly gas-permeable. With an ion beam, the SiO₂ polymerization rate is altered continuously across the array. As a result, the thickness of the SiO₂ varies from one side of the array to the other, which differentiates the gas response of the sensor elements. The now different sensor elements exhibit conductivity patterns dependent on the type and quantities of the gases contained in the ambient atmosphere of the sensor system. A temperature gradient across the sensor array is applied for additional sensor differentiation.In order to control this IBAD SiO₂ preparation, different beam positioning techniques were applied and the influence of pressure and deposition time was studied. The SiO₂ membranes were prepared on some 100 nm thick SnO₂ or WO₃ layers that had been reactively sputtered onto an oxidized silicon substrate. To obtain SiO₂ of high gas permeability, in all cases phenyl-triethoxy-silane was applied as precursor, with the substrates kept at room temperature. SiO₂ films between 1 nm and nearly 100 nm thickness were prepared. The thickness was varied by several 10 nm across the 9 mm wide metal oxide field and examined with regard to its influence on the gas sensor response. The gas-detecting properties were examined for optimization by exposing the SiO₂-coated microarray to model atmospheres.
11:10 AM		B5-9 Intrinsic Stress in Ion Synthesized Materials M. Nastasi (Los Alamos National Laboratory) The presence of intrinsic stresses in coatings and ion modified surfaces can be shown to be related to defects, microstructure, interfaces, and incorporated impurities. Typically, thin films formed by thermal evaporation have a high void fractions (i.e., low atomic density) and are in a state of residual tensile stress. Experience has shown that when thermally evaporated films are deposited with the aid of an ion beam, the microstructure begins to densify allowing even higher attractive interactions between adjacent atoms which can further increase the tensile stress to a maximum. Under high flux ion bombardment significant atomic compaction can occur, resulting in greatly increased densities which can drive the stress levels to a highly compressive state. In general most of these processes are assumed to occur athermally. However, past and recent experiments have shown that ion irradiation not only stimulates the evolution of stress, but that the evolving stress impacts the kinetics and thermodynamic driving forces which are responsible for steady state configuration of the material. In this paper we explore the atomic origins of stress and examine how ion bombardment can be used to engineer the stress in ion synthesized materials.
11:50 AM		B5-11 Formation of Carbon Nitride Films by Means of Simultaneous Positive and Negative Ion Beam Deposition Y.H. Horino, N.T. Tsubouchi, B.E. Enders, C.H. Heck, A.C. Chayahara, A.K. Kinomura (Osaka National Research Institute, JAPAN) Dual ion beam deposition apparatus was newly developed. The machine consists of a positive ion beam line, a negative ion beam line and an ultra-high vacuum deposition chamber. The machine can generate mass-analyzed very low energy ion beams, energy range covers 10eV to 20keV, with positive and negative charges at the same time. It is possible to deposit these ions directly on a substrate not only simultaneously but also alternatively or independently. The machine has a wide applications to fabricate such as ultra-pure materials or non-traditional materials. The machine is also useful to study fundamental processes of ion beam deposition and/or ion solid surface interactions. Using this new apparatus, isotopically pure carbon nitride (CxNy) films were fabricated by C^- and N⁺ ions deposition simultaneously. The ion energy was varied from 50 to 400eV. The films were analyzed by Rutherford backscattering (RBS), Fourier Transform Infrared spectroscopy (FTIR) and Raman scattering. It was found that the composition ratio (N/C)_C become to saturate to about 0.9 after arrival ratio (N/C)_A comes over 1. It was also found that the film has an amorphous-carbon like structure and the amount of C-N triple bonds tended to decrease with decreasing nitrogen ion energy where the energy of carbon ion was fixed.
12:10 PM		B5-12 Optical Thin Film Coatings: Influence of Ion-Mass and Energy During the Ion-Beam-Assisted Deposition A. Rizzo (Pastis-CNRSM, Italy); M. Alvisi (INFM - University of Lecce, Italy); F. Sarto, S. Scaglione (ENEA, CRE-Casaccia, Italy); L. Vasanclli (INFM-University of Lecce, Italy) The dual ion beam sputtering technique is a promising method to fabricate optical coatings that need a good control of performance. Ion assisted thin film, working in the UV region of the spectrum of an increases of absorption coefficient and scattered values of refractive index. The different suttering yields of the film elements can be considered as the main responsible of these detrimental effects. In this work, the influence of ion beam assistance on ZrO₂, SiO₂ and HfO₂ thin film deposition is investigated. The sputtering yield has been measured by varying the mass (Ar, Xe) and energy (100-1000 eV) of the bombarding ions of the assistance gun. The yield measurments were compared with the calculated yields using Sigmund's model. Different screening functions for different characteristic energy ranges were needed to fit the experimental results. There is a window in the range of the energy of the ion beam which enhances the film quality without influencing the stoichiometry.
12:30 PM		B5-13 Structural Investigations of Chromium Nitride Films Formed by Ion Beam Assisted Deposition W. Ensinger, K. Volz (University of Augsburg, Germany); M. Kiuchi (OsakaNational Research Institute, Japan) Chromium nitride films which are well suitable for tribological and corrosion protection have been formed by electron beam evaporation of chromium under simultaneous nitrogen bombardment. The structural and phase composition of the resulting films depends strongly on the nitrogen ion energy used. Films which were prepared with the same ion to atom ratio, but different nitrogen energy of 10 and 30 keV, respectively, are compared. The morphology is determined by cross section transmission electron microscopy, the phases by transmission electron diffraction. Without ion irradiation, a chromium film is formed on the silicon wafer, which is composed of columnar grains with open grain boundaries. Ion irradiation with an energy of 10 keV results in the formation of a finecrystalline c-CrN film on the Si-wafer. Increasing the ion energy to 30 keV leads to a layered growth of the CrNx film. The lower part of the film consists of CrN, but there is a chromium metal film oserved on top of the CrN film, due to the high ion energy used. The structure of the films directly influences its ability as a protective anti-corrosion coating.