Papers

ICMCTF2001 Session B5-1: Hard Surfaces and Ion Beam Technologies

Thursday, May 3, 2001 8:30 AM in Room Golden West

Thursday Morning

Start	Invited?	Item
8:30 AM		B5-1-1 Self-Healing Properties of Corrosion-Resistant Metal Nitride Coatings Deposited by Ion Beam Assisted Deposition J.D. Demaree (Army Research Laboratory) Passive films formed on chromium nitride coatings during aqueous corrosion have been shown to contain significantly larger amounts of chromate oxyanion species than those formed on chromium coatings. In part because of this, chromium nitride coatings can provide greater corrosion resistance than chromium, since these oxyanions act to deprotonate and strengthen the passive oxide, as well as retard the ingress of aggressive chloride ions from the solution. Chromate oxyanions are also known to be strong corrosion inhibitors, forming insoluble salts with many metal cations, such as iron. The "self-healing" action of mobile oxyanions like chromate will help produce a protective metal coating that is not only corrosion resistant, but remains protective in the presence of coating defects such as pinholes or in-service scratches. In this study, coatings of Cr-N, Mo-N, and Cr-Mo-N have been synthesized with ion beam assisted deposition (IBAD) in an attempt to understand the synergism involved in the production and incorporation of protective chromate and molybdate oxyanions. The coatings were deposited onto both inert (glass) and metal substrates using a dual e-beam evaporation system with an RF gridded ion source. The coatings were examined using standard electrochemical techniques, and the passive films formed during anodic polarization were examined using x-ray photoelectron spectroscopy (XPS). In addition, the self healing properties of the coatings were examined by creating pinhole-type defects in the coating, exposing the sample to a corrosive environment, and examining the exposed steel surface using XPS and secondary ion mass spectroscopy (SIMS) for the presence of migrating chromate and molybdate species.
9:10 AM		B5-1-3 A Compact Apparatus for Coating the Inner Walls of Tubes and Cylinders by Ion Beam Sputtering W. Ensinger (Philipps-University Marburg, Department of Chemistry and Materials Science Center, Germany); Ch. Sundermann, O. Lensch, B. Enders (Philipps-University Marburg, Germany) The present paper describes an apparatus for coating the inner walls of tubes. Tubes are often required to exhibit better performance in corrosion and wear behaviour than the material the tube is made of can offer. The situation can be improved when the tube is coated with a protective film. However, coating the inner walls of tubes by means of physical vapour deposition techniques is difficult because the material to be deposited has to enter the tube under very flat angles to the wall normal, depending on the ratio of tube inner diameter and tube length. This problem can be overcome when the source of the material to be deposited is located inside the tube. This is possible when sputter coating with ions is performed. A sputter target is located inside the tube. Energetic ions are accelerated into the tube and impinge onto the target. Thus, material is sputtered from the target onto the inner walls of the tube. The apparatus consists of an ion source, either a Penning-type cold cathode source for gases, or a MEVVA-type ion source for metal ions, with an ion extraction and acceleration system for up to 50 kV. It is directly connected to a vacuum chamber, consisting of a stainless steel tube with vacuum pumps at each end. Tubes with a length up to 1 m can be placed inside it. Form the rear-side, a sputter target is pushed through the tube. As an example, a steel tube with 1 m length and a glass tube with 1 m length were coated with thin amorphous carbon films. Adhesion measurements with the pin-pull test showed that the films were well adhering. Corrosion tests in aqueous media showed that the films exhibited a low microporosity with good corrosion.
9:30 AM		B5-1-4 Structural Modifications of Hafnium Oxide Films Prepared by Ion Beam Assisted Deposition under High Energy Oxygen Irradiation S. Miyake, I. Shimizu, R.R. Manory (Osaka University, Japan); G. Kimmel (Ben Gurion University, Israel) This work deals with high-energy ion beam assisted deposition (IBAD) of HfO₂. A metallic hafnium target was used to generate hafnium vapor with simultaneous bombardment with oxygen ions, accelerated between 1-20keV, a much higher energy regime than in other IBAD works. The transport ratio (TR), defined as the ratio between the hafnium arrival rate and the oxygen ion dose, was varied in the range of 0.5-10. The substrate was not heated during deposition. The films structure and properties were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering (RBS), electron probe micro-analysis (EPMA), microhardness and pin-on-disc testing. Significant structural modifications were observed with parameter variation. Films consisting solely of a cubic CaF₂-type structure were repeatedly obtained at a TR value of 5. To the authors' knowledge this is the first report of this high temperature structure at room temperature. At other TR values increasing amounts of the monoclinic phase were obtained. Measurements of film stoichiometry show that the films are oxygen deficient; the Hf:O ratio appears to be at a constant value of about 1:1.5 despite variations in TR. At 20 keV acceleration energy microhardness increased linearly with TR, reaching a maximum of 25GPa at a TR value of 10.
9:50 AM		B5-1-5 Al₂O₃ Gradient Coatings Produced by IBAD as Gaspermeable Membranes for an Electronic Nose Microsystem M. Frietsch, T. Schneider, V. Trouillet, J. Goschnick (Forschungszentrum Karlsruhe GmbH, Germany) IBAD (Ion Beam Assisted Deposition) was used to deposit Al₂O₃ membranes with a thickness gradient on a gas sensor microarray of high integrity which was developed at the Forschungszentrum Karlsruhe. The microarray, currently comprising 38 sensor elements on an area of 4 by 8 mm, is based on gas-sensitive, sputtered SnO₂ or WO₃ thin films. The metal oxide films are subdivided by parallel, sputter-deposited Pt electrode strips for measuring the electrical conductivity of the metal oxide which sensitively depends on the ambient gas composition. This partitioning technique yields the sensor elements of the microarray in one production step. However, in order to enable gas-recognition each sensor element has to exhibit a different selectivity of the gas response. Our previous work demonstrated, that coating the microarray with a gradient membrane, i.e. showing a thickness variation across the sensor elements, results in a differentiation of the gas-sensing properties of the sensor elements. IBAD is an advantageous method to produce such gradient membranes as this method allows lateral structuring of the films using different shapes of the activating ion beam. So far, only gradient membranes consisting of SiO₂ have been produced using IBAD. In order to test other membrane materials that allow different tuning of the gas sensor response, Al₂O₃ coatings were produced in this work using aluminum-tri-sec-butylate as precursor. Variations of the experimental conditions, e.g. the precursor partial pressure and the shape of the ion beam were applied and the influence on the film composition and the thickness gradient was investigated with the aid of ellipsometry and Secondary Neutral Mass Spectrometry (SNMS).
10:30 AM		B5-1-7 Industrial Applications of Ion Implantation on Tools B. Torp (Triion A/S, Denmark) Ion Implantation is becoming a standard treatment for solving different wear and corrosion problems of tools especially in areas where dimensions and extreme sharpness are essential. A short description of the ion implantation process and a state-of-the-art Industrial Ion Implanter will be given, together with a description on how ion implantation can be implemented along with PVD. Some examples of applications including performance data will be given, among the applications are: Implantation of plastic molds for solving abrasive wear and corrosion problems. Implantation of forming tools for making tin cans etc. Implantation of cutting tools for meat, fish, paper, rubber etc. Implantation of cutting tools for aluminum machining. Implantation of wood cutting tools. Finally it will be discussed in which areas further research is needed in order to understand the applications of ion implantation, e.g. implantation of cemented tungsten carbide tools, where initial studies will be presented and discussed.
11:10 AM		B5-1-9 The Effect of Transport Ratio and Ion Energy on the Mechanical Properties of IBAD Niobium Nitride Coatings M.L. Klingenberg (Concurrent Technologies Corporation); J.D. Demaree (Army Research Laboratory) Niobium nitride films were produced using low (90 eV) and moderate (750-800 eV) energy nitrogen ion beams of varying transport ratio, i.e., ion to atom arrival ratio. The approximate transport ratios that were used included 1.0, 0.75, 0.50, 0.33, 0.25, 0.125, and 0.062. The resulting structure, material phase, and composition of the films were characterized using scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM), and Rutherford backscattering spectrometry (RBS) techniques. The tribological properties of the films, including adhesion, hardness, modulus of elasticity, coefficient of friction, and wear resistance were assessed.
11:30 AM		B5-1-10 Microstructure, Nano-Hardness, and Resistivity of Chromium Nitride Thin Films Deposited on Silicon using Ion-Beam-Assisted-Deposition Method C.-H. Ma (University of Illinois at Urbana Champaign); J.-H. Huang (National Tsing Hua University, Taiwan, ROC); H. Chen (University of Illinois at Urbana Champaign) Highly (200) oriented Chromium Nitride (CrN) thin films have been grown on Si by Ion-Beam-Assisted-Deposition (IBAD) method. The processing conditions, such as substrate temperature, ion (N₂⁺ and N⁺) to metal (Cr) ratio, ion beam incident angle and energy, are selected to enhance the growth of CrN phase vis-a-vis the Cr₂N phase. Microstructure, preferred orientation and composition of grown films were examined using X-TEM, SEM, AFM, XRD, XPS and RBS techniques, and are correlated to their mechanical and electrical properties. Nano-hardness, residual stress and resistivity were measured. Amount of residual stress, grain size, microstructure and composition were found to change with deposition parameters. The optimal conditions to grow CrN/Cr₂N films with a dense columnar structure and high hardness were discussed.