Papers

AVS1996 Session VM+TF-ThM: Thin Film Hard Coatings

Thursday, October 17, 1996 8:20 AM in Room 104A/B

Thursday Morning

Start	Invited?	Item
8:20 AM		VM+TF-ThM-1 Properties of TiN/Pd Multilayer and Alloy Thin Films S. Rohde (University of Nebraska, Lincoln); A. Matthews (University of Hull, England); M. Nassir (University of Nebraska, Lincoln); A. Leyland (University of Hull, England) Stimulated by the research of several groups such as, Korhonen and co-workers at Helsinki University of Technology, Jehn and co-workers at the FEM Institute in Germany, and others, TiN thin films (less than 3\microns\) with sub-micron Pd interlayers were deposited using both reactive magnetron sputtering and reactive ion plating onto mild steel substrates. The corrosion resistance and wear behavior of the resulting films were evaluated, and the relative strengths and weaknesses of the two deposition techniques compared. Several alloy TiN/Pd films were also deposited and their wear and corrosion resistance is compared with that of the layered films. Microstructural, chemical, and mechanical properties of the coatings were examined using hardness testing, scratch adhesion testing, SEM/EDAX, x-ray diffraction, and AES.
8:40 AM		VM+TF-ThM-2 Deposition and Characterization of TiB\sub 2\ and Ti-B-N Films T. Zhang, M. Wong, W. Sproul, M. Wu, Y. Chung (Northwestern University) TiB2 and Ti-B-N films on various substrate materials were synthesized using ionized dc-magnetron sputtering TiB2 target in argon or argon-nitrogen mixtures. A two-turn coil powered by 13.56 MHz rf was placed between the target and the substrate table to enhance the ionization fraction of the plasma. The structure and properties of the TiBx films are affected by several of the reactive sputtering process variables such as substrate bias and total gas pressure and by the substrate materials. The crystallinity and hardness of the TiBx films increases with decreasing total gas pressure from 5.3 to 0.67 Pa. Well crystallized TiB2 films with strong (0001) texture and with hardness up to 50 GPa were produced. Nitrogen doping into TiBx films decreased their crystallinity and hardness. The dry ring-on-block testing of several stainless steel samples, coated with different hard materials, sliding against hardened 52100 steel ring showed the TiBx-coated samples exhibiting the lowest friction of ~0.1 and the lowest wear rate.
9:00 AM		VM+TF-ThM-3 Technology Update on Hard Coatings for Cutting Tools D. Quinto (Kennametal Inc) Scientific developments in hard coatings have been translated into successful commercial cutting tool technologies after an incubation time on the order of 5 years. The most noteworthy new commercial coatings include second- generation CVD alumina, PVD TiAlN and diamond. PVD alumina and cBN will probably be the next significant coating breakthroughs. The superhard coatings, diamond and cBN, have posed special problems relative to adhesion to the tool substrate. In this case, the micromechanisms governing adhesion are not yet well understood. These will be discussed in light of coated tool material designs that are currently successful.
10:00 AM		VM+TF-ThM-6 Influence of rf Substrate Bias on the Properties of CN\sub x\ Films Prepared by Reactive Magnetron Sputtering V. Hajek, K. Rusnak, J. Vlcek (University of West Bohemia, Czech Republic); L. Martinu (Ecole Polytechnique, Canada); S. Gujrathi (Universite de Montreal, Canada) Carbon nitride is predicted to exhibit extreme mechanical properties such as high hardness. In the present work, we systematically study the effect of RF-induced negative substrate bias voltage,V\sub B\, on the characteristics of CN\sub x\ films fabricated by dc magnetron sputtering of a graphite target in a nitrogen plasma. The CN\sub x\ films, typically 1 - 2 micrometers thick, were deposited onto Si(100) substrates at a temperature of 600 \super o\C, and a pressure of 0.15 - 5 Pa. The films' microstructure and composition were evaluated using elastic recoil detection (ERD) analysis, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, Raman scattering and atomic force microscopy (AFM). The nitrogen concentration in the films was found between 12 and 24 at. %. Increasing the \|V\sub B\\| values resulted in raising the N/C ratio, while the hydrogen (1 - 5 at. %) content decreased. The latter effect clearly demonstrates the sputter-cleaning process during the ion-assisted deposition. The films are predominantly amorphous. Spectrophotometric study of the CN\sub x\ films showed a refractive index of 1.6 - 2.1 in the visible region. Even at its low concentration, hydrogen was found to be responsible for a decrease of optical absorption in the infrared region. Mechanical properties, such as hardness and adhesion, are also studied and correlated with the films' microstructure.
10:20 AM		VM+TF-ThM-7 Ion Beam Induced Surface Graphitization of CVD Diamond for X-ray Beam Position Monitor Applications C. Liu, D. Shu, T. Kuzay, L. Wen, C. Melendres (Argonne National Laboratory) The Advanced Photon Source (APS) at Argonne National Laboratory is a third generation synchrotron facility that generates powerful x-ray beams on its undulator magnet beamlines for a variety of scientific and industrial user research programs. It is very important to know the position and the angle of the x-ray beam during experiments. Due to very high heat flux levels, a number of patented x-ray beam position monitors (XBPM) exploiting beneficial characteristics of chemical vapor deposition (CVD) diamond have been developed. These XBPMs have a thin layer of low atomic mass metallic coating to cause photoemission from the x-rays to generate a measurable current for position determination. Another concept proposed in the development has been the graphitization of the CVD diamond surface to create a very thin, intrinsic and conducting layer that can stand much higher temperatures than the coated metallic layers. A laboratory sputter ion source has been used to transfor m selected surfaces of a CVD diamond substrate into graphite. The effect of 0.5 - 3 keV argon ion bombardment on CVD diamond surfaces at various temperatures from 400 to 550 C has been studied using Auger electron spectroscopy and in-situ electrical resistivity measurements. Graphitization after the ion bombardment has been confirmed, and optimum conditions for graphitization have been studied. Raman spectroscopy has been applied to identify the overall diamond structure in the bulk of CVD diamond substrate after the ion bombardments. By using graphite masks, this technique of ion bombardment at elevated temperatures may be used to produce single-element diamond XBPMs at the APS.
10:40 AM		VM+TF-ThM-8 Determination of the Direction of Stress in a Polycrystalline Diamond Film using Polarized Raman Spectroscopy J. Mossbrucker, T. Grotjohn (Michigan State University) The knowledge of the direction of stress in polycrystalline diamond films is of interest to determine the overall properties of deposited films. The stress in polycrystalline diamond films is composed of an isotropic part and a non-isotropic part. In this paper we will show that a considerable amount of the stress usually found in polycrystalline diamond films is of the non-isotropic form. To determine the isotropic and non-isotropic part of the stress we use polarized Raman spectroscopy to measure the diamond Raman signal wavenumber and width in order to characterize the polycrystalline diamond film. To determine stress direction the crystal orientation of the measured crystal must be known. This also is done using polarized Raman spectroscopy. Therefore, only one measuring instrument is used to determine crystal orientation and stress direction. A detailed description of the measuring and data analysis processes are given. Polarized Raman spectra of different individual crystals within the polycrystalline film are presented and the results of the determination of the crystal orientation and the direction of the stress are given.
11:00 AM		VM+TF-ThM-9 Evidence of Aging Effects in Sputtered ZrN Films from Positron Annihilation J. Brunner (ETH-Zurich, Switzerland); A. Perry (ISM Technologies, Inc.) The lifetime of positrons in a lattice is strongly affected by structural defects even if their concentration is beyond the limits of detection by classical methods. The lack of a repulsive center in a vacancy acts as a trap for the positron which then annihilates with reduced probability due to the lower electron density at this site. The exitence of a component longer than that of bulk annihilation in the positron lifetime spectrum thus reflects the presence of vacancies. The behavior of this long lived component in ZrN films deposited by reactive sputtering on stainless steel was monitored over a period of 18 months. During this time its value decreased steadily by a factor of 2-3 depending on the negative bias applied during the film deposition process. No significant changes in the colour were observed during the measurements. A tentative explanation is the growth of polyvacancies or voids at the expense of monovacancies.
11:20 AM		VM+TF-ThM-10 Properties of ZrO\sub 2\ Films on Sapphire Prepared by ECR Oxygen Plasma Assisted Deposition S. Moulzolf, Y. Yu, D. Frankel, R. Lad (University of Maine) ZrO\sub 2\ films are used as hard coatings for such applications as recording media, engine components, tooling, bearings, and machine parts. Tetragonal zirconia precipitates in bulk alumina enhance its mechanical strength through a martensitic-like transition whereby the tetragonal phase ZrO\sub 2\ tranforms to a monoclinic phase and dissipates the energy of propagating cracks. We have grown tetragonal phase ZrO\sub 2\ in thin film form on r-cut sapphire (\alpha\-Al\sub 2\O\sub 3\) using electron beam evaporation of Zr in the presence of an electron-cyclotron-resonance (ECR) O\sub 2\ plasma. Films were grown between room temperature and 800\super o\C and thicknesses ranged from the nanometer to micron regime. Structure and composition were assessed using in situ RHEED, AFM and XPS. An ECR oxygen treatment of the sapphire substrate prior to growth provides a highly ordered stoichiometric surface. ZrO\sub 2\ growth below 300\super o\C yields amorphous films; they remain amorphous upon post-deposition annealing treatments to 800\super o\C. At higher growth temperatures, the ZrO\sub 2\ initially grows epitaxially in the tetragonal phase with the (001) plane oriented parallel to the (10-12) substrate as evidenced by RHEED. This metastable tetragonal phase is present for thicknesses up to 40 nm. At higher coverages, RHEED patterns indicate a new phase coexisting with the tetragonal phase that is consistent with the equilibrium monoclinic phase. AFM images of 100 nm thick crystalline films reveal elongated ZrO\sub 2\ crystallites on the order of 70 nm by 100 nm with a surface roughness on the order of 4 nm.
11:40 AM		VM+TF-ThM-11 Growth of Stoichiometric Al\sub 2\O\sub 3\ Thin Films by Controlably-Unbalanced Magnetron Sputtering of a Non-oxidized Al Target in Ar/O\sub 2\ Gas Mixture U. Helmersson, I. Ivanov, K. Mac\aa a\k (Link\um o\ping University, Sweden) \Alpha\-Al\sub 2\O\sub 3\ thin films have been grown using controlably-unbalanced reactive dc magnetron sputtering of an aluminum target in Ar/O\sub 2\ discharges onto fused quartz substrates. An additional solenoidal coil was used to create a magnetic field of approximately100 G in the substrate vicinity, leading to a drastic increase of the substrate ion current density to a value of 2.5 mA cm\sup -2\ as compared to 0.1 mA cm\sup -2\ obtained without the coil. The large amount of low-energy ions impinging on the growing film surface resulted in an increased oxygen gas incorporation, probably as a result of an increased impact-induced chemisorption rate of oxygen on the film surface. Single phase \alpha\-Al\sub 2\O\sub 3\ films could thus be deposited while operating the target in the non-oxidized metallic mode. In this way an as high-growth rate of the oxide as that of the pure aluminum could be obtained, furthermore sparking effects on the target could be totally avoided.