Papers

AVS2004 Session PS2-MoA: Emerging Plasma Applications

Monday, November 15, 2004 2:00 PM in Room 213B

Monday Afternoon

Start	Invited?	Item
2:00 PM		PS2-MoA-1 Dielectric Barrier, Atmospheric Pressure Glow Discharges (DB-APGD) : Applications, Diagnostics and Modeling M.R. Wertheimer, I. Radu (Ecole Polytechnique de Montreal, Canada); R. Bartnikas (Hydro Quebec Research Institute, Canada) The field of "cold" (non-equilibrium) plasmas at atmospheric pressure (AP) is receiving much attention, in part due to the reward of more economic processing without vacuum systems. Dielectric barrier discharges (DBD) are a particularly promising subgroup; among these, AP glow discharges (APGD) occur in certain gases with long-lived energetic states, for example in N₂ and in the noble gases. They manifest several remarkable peculiarities, described below, and they have opened application areas as diverse as (a) polymer surface modification, (b) deposition of novel thin film materials, (c) short wavelength light sources for photochemistry, (d) plasma displays, and numerous others. The presentation commences with a short overview of these recent industrial innovations; we then describe fundamental and applied research on DB-APGD in this laboratory. In the former category, diagnostic and modeling studies in helium are briefly presented : (i) At low applied a.c. voltage, V, a single, multi-µs current pulse per half-cycle occurs, but the "glow" may comprise many geometrically-ordered plasma columns which ignite and extinguish in perfect synchronism; (ii) at higher V, these merge into a "true" APGD, spread uniformly over the entire electrode area. (iii) Under specific conditions of V and the a.c. frequency, f, a "pseudoglow" regime sets in, comprising two or more pulses of monotonically decreasing amplitudes per half-cycle. We explain observations (i) to (iii) and demonstrate excellent agreement between experimental measurements (e.g. spatial and temporal evolution of the discharges) and the two-dimensional theoretical model developed by Novak and Bartnikas. Finally, turning to applied research, the unique capabilities of DB-APGD processing of materials is illustrated with several examples drawn from categories (a), (b) and (c) identified above.
2:40 PM		PS2-MoA-3 Hot Hollow Cathode Diffuse Arc Deposition of Chromium Nitride Films H. Barankova, L. Bardos, L.-E. Gustavsson (Uppsala University, Sweden) The hollow cathode in the diffuse arc regime (arc with hot thermionic cathode) was used for deposition of chromium and chromium nitride films. The chromium hollow cathode serving as a gas inlet was connected to a radio frequency (rf) generator with the rf power up to 350 W. The process of generation and performance of the hollow cathode discharge and its transition to the arc regime was examined for different gases. The comparison is also given with other target metals. The reactive process of CrN deposition was investigated. Films were deposited on unheated silicon and steel substrates. Highly oriented crystalline CrN films were deposited at retes up to 4.5 μm/min. The effect of process parameters and their correlation to properties (microcrystalline structure, hardness and deposition rate) of CrN is given.
3:00 PM		PS2-MoA-4 Atmospheric Plasma Deposition of Abrasion Resistant Coatings on Plastic G. Nowling, M. Moravej, M. Yajima, R.F. Hicks, X. Yang (University of California, Los Angeles); S. Babayan (Surfx Technologies); W. Hoffman (Motorola) {The plasma-enhanced chemical vapor deposition of silicon dioxide on plastic has been examined in an atmospheric pressure discharge operating with 2.0 vol.% oxygen in helium, at 100 W RF power, and a gas temperature of ~100°C. Several silicon precursors were studied, including tetramethyldisiloxane (TMDSO), tetramethyl-cyclotetrasiloxane (TMCTS), tetraethoxysilane (TEOS), hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSN). After growth, the thickness, refractive index, composition, and structure of the films were determined by ellipsometry, infrared spectroscopy, and three-dimensional surface imaging. Hardness and abrasion tests were performed as well. Glass films could be deposited at rates up to 1.0 micron/minute using TMDSO. However, these films contained significant amounts of carbon and hydrogen, and abraded easily during scratch tests. Feeding HMDSN to the oxygen plasma resulted in the deposition of SiO₂ films that were free of nitrogen and carbon, contained minimum hydroxyl concentrations, and displayed excellent hardness and scratch resistance at a film thickness >1.5 microns. The maximum deposition rate obtained using HMDSN was 0.3 microns/minute. At the meeting, we will discuss the relationship between the plasma chemistry and the properties of the glass coatings.}
3:20 PM		PS2-MoA-5 Plasma Surface Modification for In-line Commercial Applications A. Yializis, R.E. Ellwanger (Sigma Technologies Int'l Inc.) Plasma is the most common state of matter in the visible universe and has been used for decades in commercially important processes. However, such processes have historically tended to be limited to fairly small scale vacuum applications. The idea of using plasma, particularly atmospheric plasma, to add substantial value to a product by modifying the surface of a moving substrate with either added functionality or a thin functional coating is indeed compelling. Emerging applications include elevation of surface energy to promote adhesion or wetability, ablation to remove unwanted residue or material, sterilization, and deposition of a thin functional coating. Sigma Technologies has been at the leading edge of efforts to commercialize these concepts for the past several years and recent results in the aforementioned application areas are presented.
4:00 PM		PS2-MoA-7 Fundamental Aspects on the Sputter Efficiency in High Power Pulsed Magnetron Sputtering U. Helmersson, J. Alami, J. Böhlmark, M. Lattemann (Linköping University, Sweden) The use of high power pulsed magnetron sputtering (HPPMS) is an elegant way of producing a large amount of ions from the sputtered materials in magnetron sputtering (MS). HPPMS has great potential in thin film deposition where there is a desire to control direction, lateral distribution, and arrival energy of the depositing species. In this paper we present measurements of the deposition rate using HPPMS and comparing it with normal dc MS. It shows that in general the deposition rate is lower for HPPMS using the same average input power and that the deposition rate scales with the self-sputtering yield of the sputtered material in use. This can be understood in view of the large fraction of ionized metal in the close vicinity of the cathode and that the metal itself will be responsible for a large fraction of the effective sputter ejection of the cathode material. The observed results are also discussed in view of the pulse power and inert gas pressure used.
4:20 PM		PS2-MoA-8 RF Plasma Deposition of Thin SiO_x Films onto Aluminium Alloy: XPS and Contact Angle Measurements Studies A. Azioune, M. Marcozzi, V. Revello, J.-J. Pireaux (Lise Namur, Belgium) Protection of (metallic) substrates via paints is widely used in many sectors including the aerospace industry. The efficiency of the process depends on the durability of the paints and on the properties of the interface between the organic layer and the surface metal oxides; thus, the pre-treatment of the aluminium alloy prior painting is a very important step to long term - performance for this technology. However, most of the pre-treatments used now on the aluminium present environmental drawbacks as they are based on solvents and chromates. An alternative efficient and ecologically cleaner method is the plasma technology. In the present work, the aluminium substrates (Al-clad 2024) were cleaned by RF (13.56 MHz) plasma, from a mixture of oxygen and argon gases. It is observed that the carbon contamination is completely removed using Ar plasma. Thin SiO_x films have been deposited by plasma a mixture of hexamethyldisiloxane (HMDSO) and oxygen (20 W, 5 min). In the absence of oxygen, a thick (> 10 nm) and superhydrophobic (θ ≥ 100°) film characteristic of PDMS properties is formed; polysiloxane-like thin ( < 10 nm) films (SiO_x) are obtained with the introduction of oxygen (20, 50 and 80%). Both XPS and contact angle measurements confirmed both the composition and the structure of these films. More importantly, contact angle measurements using different liquids and interpreted with the van Oss Good Chaudhury theory, allowed to determine the surface free energy of the deposited films: the calculated surface tensions (γ _s, γ _s ^d, γ_s ⁺ and γ_s ^-) of the film formed from HMDSO/O₂: 50/50 are in excellent agreement with those of reference silicium oxide substrates. This work is supported by Walloon Region (RW n° 021/5208) in the framework of a collective reasearch project "ECOPO" in collaboration with Université de Mons-Hainaut and Coating Research Institute.
4:40 PM		PS2-MoA-9 Transparent Hybrid Inorganic/Organic Barrier Coatings for Plastic OLED Substrates T.W. Kim (GE Global Research Center); M. Schaepkens (GE Advanced Materials); M. Yan, A.G. Erlat, M. Pellow, P.A. McConnelee, T.P. Feist, A.R. Duggal (GE Global Research Center) The use of plastic film substrates enables fabrication of new applications in the area of flexible opto-electronics, such as flexible display and lighting, using low cost roll-to-roll fabrication technologies. One major limitation of bare plastic film substrates in these applications is the rapid oxygen and moisture diffusion through the substrates and subsequent moisture and oxygen induced degradation of the opto-electronic devices. Recently GE has developed a novel coating technology to reduce the moisture permeation rate through the plastic film substrate below 5x10^-6g/m²/day using plasma enhanced chemical vapor deposition. Unlike other ultra-high barrier(UHB) coatings comprised of inorganic and organic multilayer, GE's UHB coating comprises a single layer of hybrid inorganic and organic materials. In this single layer, the composition is periodically modulated between silicon oxynitride and silicon oxycarbide. In addition, the transition from one material to the other is continuous, which results in a graded composition structure, so that there is no distinct interface between them. In contrast, other multilayer UHB coatings, where inorganic and organic materials are bound by relatively week van der Waals force, have sharp interface, which sometimes results in delamination of layers especially during the thermal cycle. Hardness and modulus of silicon oxynitride and silicon oxycarbide are tailored such that they are similar to those of typical glasses and thermo plastics, respectively. Modeling studies suggest that the polymer-like silicon oxycarbide enriched zone decouples the pinhole defects in the silicon oxynitride enriched zone compelling tortuous paths for moisture diffusion, and thus reduces the moisture permeation rate by seven orders of magnitude as compared to that of uncoated plastic substrates. GE's UHB coating also has superior visible light transmittance and color neutrality suitable for the use of display and lighting substrates.
5:00 PM		PS2-MoA-10 Mass Spectrometric Determination of the Mechanism of the Chemically-Enhanced Reaction of Hydrogen Plasmas and Propellant Surfaces. R. Blumenthal, R. Valliere (Auburn University) The erosion rate of sprayed-on films of the propellants RDX and HMX under hydrogen plasma exposure are more than one-hundred times the erosion rate in similar argon plasmas. Varying the plasma components impingent on the propellant surface (i.e. ions, radicals, electrons and light) by changing the sample bias and shielding the propellant surface reveals a number of strong synergistic interactions between the individual plasma components in the erosion of the film. Early supersonic pulse, plasma sampling, mass spectrometric studies have indicated that the erosion rate has both a fast and a slow component, but interferences in the mass spectrum have prevented the unambiguous identification of the products, and hence, the chemical mechanism. In this work, the volatile products collected during the erosion of isotopically labeled RDX and HMX will be presented along with a chemical/physical mechanism for the reaction.