Papers

ICMCTF1999 Session E5/D4-2: Properties and Applications of Diamond, Diamondlike and c-BN Coatings

Tuesday, April 13, 1999 1:30 PM in Room California

Tuesday Afternoon

Start	Invited?	Item
1:30 PM		E5/D4-2-1 Growth and Tribological Properties of Amorphous H-Carbon Nitride Produced by Ion Beam Technique R.L.C. Wu (K Systems Corporation); K. Miyoshi (NASA Lewis Research Center); W.C. Lanter, J.D. Wrbanek (K Systems Corporation); C. DeJoseph (Air Force Research Laboratory) Recently there has been a growing interest in ion beam processing for surface modification of base materials. Carbon nitride thin films (CN_x, H-C:N_x) are of particular interest for their applications in tribology, wear resistance, and microelectronics. In an effort to develop suitable solid lubricants used in space-like environments, a 20-cm diameter RF excited (13.56 MHz) ion gun and a four-axis substrate scanner was used for the deposition of amorphous H-carbon nitride films (a-H:C:N) by the direct ion beam technique. Mixtures of methane and nitrogen were used to generate various hydrocarbon and nitrogen-containing ions. The effects of RF power (100-600W), N₂/CH₄ gas mixture (0.2-3.0), total pressure, and ion energy (200 - 1750 eV) on the film deposition rate and tribological properties has been investigated. A quadrupole mass spectrometer and a total ion current measuring device were utilized to monitor the ion compositions of the gas mixtures of CH₄/N₂ during the deposition for quality control and process optimization. In general, the film growth rate was found to decrease with increasing ratio of N₂/CH₄ and increasing RF power. As the ratio of N₂/CH₄ increased to one or greater, there was no film formation. The predominate ion species in the gas mixture of N₂/CH₄ is CH₃⁺, and as more nitrogen was added into the ion source with CH₄, the ionic species of N₂⁺, N⁺, NH₄⁺, NH₃⁺, NH₂⁺, HCN⁺ , CN⁺ and N₂H₂⁺ were relatively increased. RBS, proton recoil techniques, FTIR, ellipsometry, SEM, and surface profilometry were used to analyze the as-deposited films. Unidirectional sliding friction experiments in UHV, in humid air and in dry nitrogen were conducted to examine the friction and wear behavior of these films. The tribological properties of H-CN_x films will be compared with those of our PCD and DLC films studied previously. The correlation between the deposition parameters on the amorphous H-carbon nitride film growth rate and their tribological properties will be presented and discussed.
2:10 PM		E5/D4-2-3 Ultra Thin DLC Films for Use as Thin-film Magnetic Disk Overcoats X. Chu (MMC Technology Inc); B. Zhang, K. Johnson (Consultant) Sputtered diamond-like carbon (DLC) films of 100 to 200 Å are in general use as protective coatings on thin-film magnetic recording disks. The standard DLC material is deposited by magnetron sputtering carbon in the presence of hydrogen and/or nitrogen. Increasing areal density in magnetic hard drives requires thinner overcoats to reduce head-medium spacing loss. Functional overcoats with thickness of 50 Å will be needed for the next generation recording medium. Tribological performance of sputtered carbon films suffers at values below 100 Å because of degradation in physical properties. Alternative deposition techniques, such as ion-beam deposition, create denser and harder films with improved physical and tribological properties. In this paper, we will present data on the deposition and characterization of 30 Å to 50 Å DLC films deposited both by sputter and ion-beam deposition (IBD) processes. Process parameter effects on structure and mechanical properties of sputtered CNx films and ion beam deposited CHx films were studied. XPS, ELLS, and Raman spectroscopy were used to characterize film microstructure and showed the sputtered CNx film to be mostly sp2 bonded. Tribology of the films was tested using Contact Start Stop (CSS) testers and the resulting carbon wear is correlated to an AFM nano-wear test. 30 Å ion-beam deposited CHx films showed good CSS tribological performance comparable to 100 Å sputtered film.
2:30 PM		E5/D4-2-4 Tetrahedral Amorphous Carbon Ultra-Thin Film as Slider ABS Overcoat for High Areal Density AMR/GMR Magnetic Recording H. Han, F. Ryan (Read-Rite Corporation); M. McClure (Commonwealth Scientific Corporation) Areal density in magnetic recording has been increasing at a phenomenal rate over past 20 years. In order to achieve 10 Gbits/in2areal density and beyond, magnetic spacing between disk and head must be on the order of 25 nm or less, which requires Sub-50 Å overcoats on both media and recording head air bearing surface (ABS). These overcoats act as protective coatings in order to avoid corrosion of magnetic alloys as well as wear which may occur when slider contacts with rigid disk during turn-on or shutdown of disk drive. Sub-50 Å thick tetrahedral amorphous carbon (t-aC) films have been deposited on both Si wafers and recording sliders by a filtered cathodic arc (FCA) system. The coatings were analyzed by RAMAN, cross-section TEM, AFM with nano-indentation/scratch attachment, contact angle and Tencor Flexus to characterize film structure, thickness and uniformity, surface roughness, wear resistance, stress, surface energy and adhesion to the substrate. Macro-particle contamination was significantly reduced and characterized by the in-house acid etch corrosion resistance test. Slider/HGA level tests were conducted in order to evaluate head tribological performance at head/disk interface (HDI), corrosion resistance, and electro-static dischage (ESD) damage by Contact Start/Stop (CSS) test, environmental soak/acid etching and Quasi-Static Test (QST), respectively. The energetic carbon ion penetration into the magnetic layer was also investigated by H-B loop tester. We conclude that Sub-50 Å t-aC overcoats prepared by FCA are a viable candidate for future high areal density AMR/GMR slider ABS applications.
2:50 PM		E5/D4-2-5 Tribological Properties of a-DLC/Ti-Based and H-DLC-Based, Functionally Graded Nanocomposite Coatings K. Miyoshi, K.W. Street (NASA Lewis Research Center); J.H. Sanders, J.S. Zabinski, A.A. Voevodin (Air Force Research Laboratory); R.L.C. Wu (K Systems Corporation) Improving the tribological functionality of diamondlike carbon (DLC) films - developing good wear resistance, low friction, and high load-carrying capacity - was the aim of this investigation. Nanocomposite coatings consisting of amorphous carbon/titanium (a-DLC/Ti) top layers and functionally graded titanium-titanium carbide-diamondlike carbon underlayers were produced on 440C stainless steel disks by the hybrid technique of magnetron sputtering and pulsed-laser deposition. Also, an amorphous hydrogenated carbon (H-DLC) was produced on the a-DLC/Ti-based, functionally graded nanocomposite coating by using an ion beam (composed of a 3:17 mixture of argon and methane) at an ion energy of 700eV. Raman spectroscopy, scanning electron microscopy, and surface profilometry characterized the resultant nanocomposite coatings. Unidirectional ball-on-disk sliding friction experiments were conducted to examine the friction and wear behavior of nanocomposite coatings in contact with 440C stainless steel balls in ultrahigh vacuum, in dry nitrogen, and in humid air. In the ultrahigh vacuum environment, the a-TLC/Ti-based, functionally graded nanocomposite coatings possessed relatively high coefficient of friction and high wear rate. On the other hand, the presence of H-DLC film markedly reduced friction in ultrahigh vacuum without sacrificing wear resistibility. The dry nitrogen and humid air caused low friction and mild wear with burnishing in both the a-DLC/Ti top layers and the H-DLC top layer.
3:30 PM		E5/D4-2-7 Tribological Behaviour of Oriented Diamond Coating / Steel Couple Under Various Environments M. Schmitt, D. Paulmier, T. Le Huu, M. El Mansori (ERMES-LPMM CNRS UMR7554, France) With its remarkable physical properties, diamond is expected to find many applications in industrial and engineering fields. A high hardness combined to a low wear rate are two of the numerous advantages which make it suitable for machining. It was then necessary to understand its tribological properties. It results from studies dealing with the frictional behaviour of diamond that the deposition method as well as the deposition parameters have a great influence on the coating properties; in particular, a modification of those parameters induces a change of the crystals growth direction. paragraph This paper presents results concerning the tribological behaviour of {111}, {110} and {100} oriented diamond coatings, obtained by combustion flame method, sliding against steel under different environments (vacuum, oxygen, water vapour, argon and hydrogen). It was proved that the crystals orientation as also the environment influence the friction process : transfers nature, disc sliding tracks, coating modifications and friction coefficients are significantly modified. The importance of the normal load was also highlighted, especially under water vapour where an artificial increase of the friction coefficient appears. SEM observations were also realised to show the surfaces changes. Raman spectrometry, EDS and EBSD analyses were carried out to confirm and explain the observed phenomena from the experimental results.}
3:50 PM		E5/D4-2-8 Boro-Nitriding of Iron and Steel by Microwave Post-Discharge Nitriding Followed by Paste Boridizing. I. Campos, E. Meléndez (UAM, Mexico); U. Figueroa, O. Salas, J.E. Oseguera (ITESM, Mexico) Armco iron and SAE 101 and 1018 steel samples were boronitrided by a combination of postdischarge nitride and paste borurizing. The treatment sequence started with nitriding at 650°C in the postdischarge flow of a plasma sustained by microwaves. In the second part the nitrided samples were borurized with a B4C based paste at 920°C. X-ray diffractometry shows the presence of B and N forming Fe2N and Fe2B compounds. During the first stage, a compact layer of nitrides that grows with a plane front. The morphology of the nitride layer does not changes after the boridizing treatment. However, the presence of boron alters the hardness profiles from the surface.
4:10 PM		E5/D4-2-9 Comparison of Structure and Microhardness of Ti2N, TiN, TiN+TiC+Ti(C,N)/DLC, TiN/DLC and TiC/DLC Films Prepared on Ti-6Al-4V Alloy by Plasma-Based Ion Implantation H. Ji, L. Xia (Harbin Institute of Technology, P.R. China); X. Ma (Harbin Institute of Technology, P.R. China); Y. Sun, M. Sun (Harbin Institute of Technology, P.R. China) The structure and microhardness of Ti₂N, TiN coatings and TiN+TiC+Ti(C,N)/DLC, TiN/DLC, TiC/DLC multilayers prepared on Ti-6Al-4V alloy by plasma-based ion implantation (PBII) with nitrogen, PBII with nitrogen, PBII with nitrogen then acetylene, PBII with nitrogen then glow discharge deposition with acetylene plus hydrogen, PBII with acetylene then glow discharge deposition with acetylene plus hydrogen respectively are compared. The corresponding film colors are found getting dimmer: light gold, gold, smoky color (uneven), light red in black (uneven), graphite black, and the corresponding surface electrical resistance is: about 1.0 * 10⁷, about 3.3 * 10⁷, 0.05-2.00 * 10¹¹, 0.016-2.400 * 10¹¹, 0.45-1.01 * 10¹¹ ohm/cm respectively. Surface oxidation is alleviated in the order of nitride (Ti₂N or TiN), TiN/DLC or TiN+TiC+Ti(C,N)/DLC, TiC/DLC films. This indicates that antioxidation ability of nitride films is poor, while existence of carbon (or carbide) improves the film antioxidation ability. There is no sharp interface between the implanted layer and the substrate. Having undergone excellent intermediate transitional region of nitrogen and carbon implantation, the top DLC layer of the TiN+TiC+Ti(C,N)/DLC multilayers formed after the carbon implantation has the best adhesion with the substrate among all the multilayers presented. But transitional effect of the intermediate nitrogen implanted region in the TiN/DLC multilayers is poor. In TiC/DLC multilayers especially, a difference between the internal stress of the top carbon layer deposited and that of the underlying carbon layer implanted has caused the multilayer properties deteriorated. These are indicated by the fact that although film microhardness increases in the order of Ti₂N, TiN, TiN/DLC, TiN+TiC+Ti(C,N)/DLC, TiC/DLC films, the TiN/DLC and TiC/DLC multilayers have demonstrated greater brittleness compared with other films presented.
4:30 PM		E5/D4-2-10 Studies on a-C:H:N Films Deposited by Chemical Vapour Deposition of Acetylene + Nitrogen for Tribological Applications K. Chakrabarti, M. Basu, S. Chaudhuri, A.K. Pal (Indian Association for the Cultivation of Science, India) During the last decade studies on amorphous hydrogenated carbon (a-C:H) films attracted much attention due to their high potential in technological applications. In the present work amorphous hydrogenated carbon films(a-C:H:N), with different nitrogen content (0 to 20 atomic percent) were deposited (deposition time 45 minutes) by chemical vapour deposition of acetylene + nitrogen onto glass/Si/quartz substrates at a deposition temperature within 523 to 623 K and bias voltage of -500 V. FTIR studies indicated the films to consist of a mixed phase of tetrahedrally bonded (sp³) and trigonally bonded (sp²) carbon atoms and the relative amounts of these two phases determine the properties of the films. The sp³/sp² ratio varied within 3 to 6 depending on the deposition environment. In the present work, we have studied the optical, electrical and mechanical properties of a-C:H:N films by measuring the band gap (1.2 to 2.2 eV), conductivity (10^-6 Ω ^-1 cm^-1) along with stress (3 to 0.5 GPa) and strain with the variation of nitrogen content in the film. The optical (Raman, photoluminescence and transmittance measurements) and electrical (hopping conductivity at low temperature) properties of the films were dominated by the π states of sp² sites which form the conduction and valence band edges and lie closer to the Fermi level. Experimental observation indicated that these sp² sites form clusters consisting of several atoms and were embedded within the σ bonded sp³ matrix. By controlling the deposition environment both sp³ and sp² bondings in the films could be controlled and the properties of the films could be tailored for tribological application. In order to ascertain the quality of the films for practical application they were subjected to tribotest.