Heinrich Hofmann, Swiss Federal Inst of Technology
Robert Pfeffer, New Jersey Inst of Technology
Mamoru Senna, Keio Univ
Rajiv Singh, Univ of Florida
Jorge Valdes, Bell Labs, Lucent Technologies
- National Science Foundation
- University of Florida
* Invited paper
SESSION CC1: PARTICULATE COATINGS:
Chair: Rajiv K. Singh
Monday Morning, December 1, 1997
Essex East (W)
8:30 AM *CC1.1
PARTICLE-PARTICLE INTERACTIONS WITH AND WITHOUT POLYMER COATINGS: Brij M. Moudgil, J. Adler, Y. Rabinovich, Materials Science and Engineering Department, University of Florida, Gainesville, FL; P. Somasundaran, Langmuir Center for Colloids and Interfaces, Columbia, University, New York, NY.
9:00 AM *CC1.2
EFFECTS OF ROUGHNESS AND MOLECULARLY THIN ORGANIC AND LIQUID LAYERS ON THE ADHESION AND FRICTION FORCES OF SURFACES. Jacob Israelachvili, Dept of Chemical Engineering, and Materials Dept, University of California, Santa Barbara, CA.
Recent adhesion and friction measurements between various surfaces, both in vapor atmospheres or totally immersed in liquids, have been carried out using the Surface Forces Apparatus (SFA) technique, which allows for these forces to be directly measured at the same time as the surface geometry (the contact area and film thickness) are measured on the nanometer scale. Both bare surfaces and surfaces coated with thin organic films (surfactant polymer) or metal oxide layers (silica, alumina, iron oxide) have been studied, and the surrounding atmosphere has been either inert vapor (dry air or nitrogen gas), humid air, or a liquid (water, hydrocarbon liquids or lubricating fluid). The results of adhesion and friction experiments reveal a rich spectrum of properties, both static and dynamic, that depend on the chemical and physical states of the surfaces, such as the roughness, the stiffness (elasticity) of the surface coating, the relative humidity (which effects capillary condensation of water in and around contacting asperities), and also the previous history. Adhesion and friction forces are often related. Also discussed will be the effects of adhesion and frictional sliding on surface damage and wear, the different types of wear mechanisms (pitting, delamination ploughing) that different surface coatings may display, and the difference in the adhesion and friction of smooth and rough (damaged) surfaces.
9:30 AM *CC1.3
INTERFACIAL CHARACTERISTICS OF NANOCOMPOSITE PARTICULATES. Krishna Rajan, Rensselaer Polytechnic Institute, Troy, NY; R.K. Singh, Univ of Florida, Gainsville, FL; P. Sajgalik, Slovak Academy of Sciences, Bratislava, SLOVAKIA.
The properties of coated particulates ultimately depends upon the nature of the interface between the core of the composite structure and the coating around the individual particle. The role of this interface becomes more significant as the surface / volume ratio increases as in the case of nanoscale particles. In this presentation, we examine some of the critical materials science challenges in controlling the chemistry and bonding at the interface in such nanoscale composites. Issues such as the potential influence of particle morphology and surface energy anisotropy on the nature of the overlayer coating especially in the nanometric size regime, is examined. This discussion is put in the context of the different approaches to the synthesis of coated particulates.
SESSION CC2: PARTICULATE COATINGS:
SYNTHESIS AND PROCESSING
Chairs: Brij M. Moudgil and Robert Pfeffer
Monday Morning, December 1, 1997
Essex East (W)
10:30 AM *CC2.1
ROLE OF PARTICLE COATINGS IN RECHARGEABLE BATTERIES. Deepika Singh, Energizer Power Systems, Gainesville, FL.
Particle coatings play a very important role in rechargeable batteries and capacitors. Particle coatings are used in various forms to make electrodes as well as to enhance their performances. Some of these electrodes are made by coating substrates with thin and thick films. The physical and chemical morphology of these particles impart electrochemical activity to the batteries and capacitors. Particulate coatings are also applied to electrodes to impart catalytic activity. In NiMH and NiCd power tool batteries, nickel particles are used to make thick films which act as conductive electrode substrates. Smaller particles of nickel are used to pre-coat perforated steel substrates to increase surface area and adhesion [INCO Process]. Better adhesion helps in improving the integrity and cycle life of these electrodes. The high capacity NiMH batteries use a foam pasted electrode as a positive. Spherical Ni(OH)2 is used as active material in these electrodes. Ni(OH)2 is a relatively poor electronic conductor. This effects the overall performance these cells. To overcome these shortcomings practical battery electrodes are fabricated in such a way that the active material is surrounded by a thin coating of an electrically conductive component to ensure the flow of electrons from the active material. This coating provides a conductive network around the non conductive Ni(OH)2 particles. The coated particles provide excellent particle to particle contact when bonded and pressed into an electrode. Moreover they do not inhibit ion transport to the active material as is required for effective electrochemical activity. Other methods of coating Ni(OH)2 in the battery industry will be discussed.
11:00 AM CC2.2
PREPARATION AND PROPERTIES OF PHENYTOIN SILICA COMPLEX NANOPARTICLES. Harumi Goto, Tetsuhiko Isobe, Mamoru Senna, Faculty of Science and Technology, Keio University, Hiyoshi, Yokohama, JAPAN.
A sparingly soluble model drug, phenytoin (5,5-diphenyl-hydantoin, denoted as PT) was added during hydrolysis and polycondensation of tetra orthoethyl silicate (TEOS). At the same time, acrylamide (AAm) was incorporated into (TESO). The primary particles of the composite was 2 3nm, Formation of hydrogen bond was confirmed by the red shift of IR adsorption band due to C=O stretching of amide group, The DTA melting peak of PT disappeared and the decomposition peak temperature increased by 28K after complex formation (CF). While the intact PT dissolved into ethanol to completion, the solubility to ethanol decreased to 55% after CF. The initial rate of dissolution into water, expressed by the time needed to dissolve 2/3 of the saturation, T2/3, increased by a factor of 7, as a result of CF. The interaction between silica and PT increased by incorporating AAm, as confirmed by the thermal analysis and the dissolution behavior. Mechanisms of enhanced solubility were discussed in terms of microstructure and chemical interaction by taking the role of AAm into account.
11:15 AM CC2.3
MECHANICALLY ASSISTED SURFACE MODIFICATION OF POLYMER PARTICLES WITH SUPERFINE CALCIUM PHOSPHATES. Jiefan Liao, Nara Machinery Ltd., Tokyo, JAPAN.
Composite materials were prepared through coating or embedding superfine calcium phosphate particles onto the surface of a more coarse polymer particle (e.g., polyethylene, 5pm) by a mechanical dry impact blending method. The calcium phosphates such as tricalcium phosphate or hydroxyapatite were synthesized mechanochemically, i.e., via grinding a binary powders mixture, e.g., Ca(H2PO4)2H20 and Ca(OH)2. Fast dehydration and amorphization of the binary mixtures took place in grinding, leading to the formation of a calcium phosphate precursor in amorphous or low crystalline state. The study reveals that the mechanochemical method is prospective in fabrication of fine calcium phosphates particles with a high surface activity, which enhances surface modification of polymer particles. The mechanisms of interparticle interactions initiated by mechanical energy is discussed in detail.
11:30 AM CC2.4
SYNTHESIS OF ENGINEERED PARTICULATES BY DRY COATING TECHNIQUE. Ali Ata, Rajiv K. Singh and Yakov Rabinovich, Department of Materials Science & Engineering, University of Florida, Gainesville, FL.
Engineered particulates were synthesized by magnetically assisted fluidization technique which produces composite particulates of primary (core) and secondary (fine) particles by creating an efficient collision environment. In the process called MAIC (Magnetically Assisted Impaction Coating), different primary particles (PMMA, Glass, Silica, Alumina, etc) of 10-200 range and secondary particles (Alumina, Titania, Silver, etc) of 0.05-1 range were used. The mechanism of coating, the effect of particle size, hardness, humidity and frequency of collisions were studied. The MAIC process was found to be an efficient and practical way of fabricating engineered particulates.
SESSION CC3: NANOSTRUCTURED MATERIALS
Chairs: Heinrich Hofmann and Mamoru Senna
Monday Afternoon, December 1, 1997
Essex East (W)
1:30 PM *CC3.1
NANOPARTICULATE COATING OF FUNCTIONAL CERAMICS BY THE VAPOR PHASE REACTION. Masanobu Awano, Tetsuya Kameyama, Mutsuo Sando, Yoshitaka K uwahara, National Industrial Research Inst of Nagoya, Nagoya, JAPAN.
Nanoparticulate coating method by the thermal plasma reaction to fabric ate functional ceramics such as oxide superconductors and synergy ceramics w as developed. Raw materials of solid and gas phases were introduced into the rmal plasma to vaporize and activate for reaction. Particles or films were d eposited on a substrate on cooling stage through the vapor-condensation proc ess. Microstructure of obtained particles and films was controlled by the co ndensation condition; injection mode of raw materials, distance between plas ma and cooling stage, substrate temperature, flow rate of plasma and sheath gas and so on. Particulate coating was successfully proceeded when the addit ional element was segregated sequentially on the particles already solidifie d. Co-condensation process from the vapor and crystallization via the liquid phase resulted in novel composite microstructures which was expected for sy nergistic enhancement on various functions. Sintered bodies fabricated from coated particles and directly deposited films of superconductors and synergy ceramics revealed improvement of their properties, respectively.
2:00 PM *CC3.2
NANOSTRUCTURED POWDERS: A NEW CLASS OF MATERIALS FOR FORMING HIGH PERFORMANCE PARTICULATE COATINGS. Ganesh Skandan, Nanopowder Enterprises Inc., Piscataway, NJ; Nick Glumac, Yijia Chen and Bernard H. Kear, Rutgers University, Piscataway, NJ.
Abstract Not Available
2:30 PM CC3.3
NOVEL METHOD FOR THE SYNTHESIS OF ATOMIC THIN FILM COATINGS ON PARTICULATE MATERIALS. J. Fitz-Gerald, R.K. Singh, University of Florida, Department of Materials Science and Engineering, Gainesville, FL.
Particulate coatings have wide- ranging applications in several new technologies such as flat-panel displays, sintering of advanced ceramics, rechargeable batteries, etc.. Here, we show the feasibility of a laser ablation technique to make very thin uniform discrete coatings in particulate systems so that the properties of the core particles can be suitably modified. Presently laser ablation techniques have been primarily applied to deposit thin films on flat substrate materials. To deposit discontinuous particulate coatings, the laser induced plume from the target comes in contact with an agitated bed of core particles (size 1-800 micron). The pressure and nature of the background gas (inert or active) controls the cluster size of the particles in the laser plume. The surface coverage and the coating of the films were found to depend on the laser parameters (energy density and number of laser pulses) as well as the residence time of the core particles in the plume regime. The films were characterized by wavelength and energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy and Auger spectroscopy techniques. These results show a very thin and uniform silver discrete coatings on alumina particles.
2:45 PM CC3.4
PROPERTIES AND MICROSTRUCTURE OF NANOSTRUCTURED SILICON. P.R.I. Cabarrocas (i), J. Dutta (ii), H. Hofmeister (iii) and H. Hofmann (ii); (i) Laboratoire de Physique des Interfaces et des Couches Minces, (UPR 258CNRS), Ecole Polytechnique, Palaiseau, FRANCE; (ii) Powder Technology Laboratory, Department of Materials Science, Swiss Federal Institute of Technology (EPFL), Lausanne, SWITZERLAND; (iii) Max-Planck-Inst of Microstructure Physics, Halle, GERMANY.
Hydrogenated amorphous silicon (a-Si:H) has several applications in the semiconductor industry and has been an active domain of research & development over the last two decades. Plasma-chemical vapour deposition from silane is generally used for all major applications of a-Si:H thin films. We have studied in great details the microstructure of cluster agglomerates in these deposition processes . Recently it has been shown that intentional inclusions of clusters into the a-Si:H thin films improved the electronic transport properties which render these new type of Si-thin film materials very interesting for applications like in photovoltaics . Here we will focus on the microstructure of the Si clusters as studied by High Resolution Transmission Electron Microscopy (HRTEM) and correlate with the formation processes. We will then attempt to discuss the optoelectronic properties with respect to the special structure of these materials.
3:30 PM *CC3.5
FABRICATION, SURFACE MODIFICATION AND PROCESSING OF NANOPOWDERS TO COATINGS AND THIN FOILS. Helmut Schmidt, Institut fuer Neue Materialien gem. GmbH, Saarbruecken, GERMANY.
Various nanoparticles have been fabricated by three different chemical synthesis routes, by microemulsion techniques, by controlled growth reactions using surface modifiers interfering with the nucleation and particle growth and by in situ synthesis from alkoxide precursors in a monomeric organic matrix system. These nanoparticles have been dispersed in organic or mixed inorganic/organic precursors to viscous systems suitable for wet coating techniques for many purposes. Due to the size of the nanoparticles the coatings, in general, are transparent. Different fields of application have been developed: ultrahard coatings on polycarbonate for new light-weight automotive glazings with taber abrader values of 2 % haze after 1000 cycles, high temperature tarnish protection coatings on stainless steel, corrosion protective coatings on aluminum alloys and low surface free energy coatings with easy-to-clean effect an various substrates.
4:00 PM *CC3.6
PREPARATION AND ELECTRONIC PROPERTIES OF MESOPOROUS OXIDE SEMICONDUCTORS. Michael Gratzel, EPFL Lausanne, Institut de Chemie Physique, Lausanne, SWITZERLAND.
Abstract Not Available
4:30 PM CC3.7
NANOSTRUCTURED ZINC SULPHIDE PHOSPHORS. R. Vacassy, S.M. Scholz, C. Plummer1, J. Dutta, H. Hofmann and M. Akinc2, Powder Technology Laboratory (LTP), Dept. of Materials Science, Swiss Federal Institute of Technology (EPFL), Lausanne, SWITZERLAND; 1Polymer Laboratory (LP) Dept. of Materials Science, Swiss Federal Institute of Technology (EPFL), Lausanne, SWITZERLAND; 2Dept. of Materials Science Engineering, Iowa State University, Ames, IA.
Zinc sulphide (ZnS) particles are efficient phosphors for application in flat-panel displays. Reducing the particle size to a few nanometer render this material a suitable candidate as a phosphor for application in low voltage display technology. ZnS nanoparticles have been prepared by precipitation from a homogeneous solution. Spherical particles of 20 to 40 nm in diameter with a very narrow size distribution were synthesized using complexing ligands such as acetate and acetylacetonate. Complexing of the precipitation cation with the anions present in the system leads to a limited concentration of free cations in solution. This strongly influenced the kinetics of the primary particle agglomeration/growth resulting in nanometer-sized ZnS particles. Nanostructured ZnS synthesized in this way, were polycrystalline, consisting of agglomerates of crystallites in the 3-10 nm size range. The synthesis of these controlled, monosized ZnS particles will be presented and discussed. The effect of Mn+2 doping on the luminescence characteristics of ZnS will also be discussed.
4:45 PM CC3.8
NANOPARTICULATE FILM PRECURSORS TO CIS SOLAR CELLS: SPRAY DEPOSITION OF CU-IN-SE COLLOIDS. Douglas L. Schulz, Calvin J. Curtis, Rebecca A. Flitton, David S. Ginley, Center for Photovoltaic and Electronic Materials and Center for Basic Sciences, National Renewable Energy Laboratory, Golden, CO.
The use of nanoparticle colloids for spray deposition of Cu-In-Se precursor films and subsequent fabrication of CuInSe2 (CIS) solar cells has been investigated. In the present study, metathesis reaction between Na2Se in methanol and the metal iodides (i.e., CuI, InI3) in pyridine produced Cu2Se, In2Se3, and CuInSe2 nanoparticle colloids. After removal of solvent, these nanoparticles were amorphous as determined by TEM and XRD and were further characterized by TGA and DSC. Purified colloid was sprayed onto heated molybdenum-coated sodalime glass substrates to form Cu2Se, In2Se3, and CuInSe2 precursor films. ICPAES showed the chemical composition of the porous Cu-In-Se precursor films is nearly identical to that of the precursor colloid. Substrate temperatures from 150 to 250C were employed for film deposition. The composition of the colloidal solvent was modified to enable good particle capture efficiencies at various deposition temperatures. The metal selenide precursor films were subjected to inert gas thermal treatments (standard and rapid) in order to promote phase formation and grain development and were characterized by XRD and SEM. CIS solar cells fabricated from thermally processed nanoparticulate precursor films exhibit solar conversion efficiencies of 4 to 5.
SESSION CC4: POSTER SESSION
Chairs: Heinrich Hofmann and Rajiv K. Singh
Monday Evening, December 1, 1997
America Ballroom (W)
CONTROL OF PARTICLE COATING PROCESSES DUE TO NANO PARTICLES INTERLAYER COATINGS. Ali Ata, James Fitz-Gerald, Rajiv Singh, University of Florida, Department of Materials Science and Engineering, Gainesville, FL.
It Is known that many properties of particulate materials are determined by controlling the surface architecture of the particles. This process is known as engineered particulates. In this proceeding we discuss the how the properties of adhesion are affected by controlling the surface architecture of particulate materials. In this research nano-thick intermediate layers were coated around primary particles via an atomic flux coating process (AFCP). This process alters the chemical nature of the surface and affects the surface architecture. The AFCP treated particles were then further coated with sub-micron sized secondary (fine) powders via a magnetically assisted impaction coating process (MAIC), to fabricate composite particles. Copper and alumina were used as primary particles (30-40 micron) and 0.5 micron alumina as secondary particles. The primary particles were coated with alumina and silver intermediate layers with the AFCP process. The results show that the alumina interlayer improves the adhesion between the primary and secondary particles due to its hydrophilic nature. The silver layers showed a reduction in the primary to secondary adhesion do to its hydrophobic nature.
STUDIES ON SURFACE-PARTICLE INTERACTIONS IN THE CHEMICAL-MECHANICAL POLISHING PROCESS. U. Mahajan, J. Adler, R.K. Singh and B. Moudgil, Department of Materials Science and Engineering, University of Florida, Gainesville, FL.
Chemical-Mechanical Polishing ( CMP ) is a new and rapidly growing process for planarization of semiconductor wafers. With the semiconductor industry moving to larger wafer sizes, CMP is the only process that assures global planarization across the entire wafer surface. Most studies on CMP have been carried out from the process viewpoint, with relatively less work having been done on the fundamental aspects of the process. In this study, we have investigated particle-surface interactions in different CMP systems. Atomic Force Microscopy ( AFM ) is used to study tungsten-alumina and silica-silica interaction forces as a function of separation distance. Effects of solution conditions, viz. pH and ionic strength are investigated. The effect of surfactants on surface behavior is also studied. Polishing experiments have been carried out on a CMP process simulator to verify the AFM results.
LASER ASSISTED NANOSTRUCTURED COATING OF COLOSSAL MAGNETORESISTIVE LA-CA-MN-O SYSTEM ON MICRON SIZED PARTICLES. D. Kumar, J. Fitz-Gerald, R. Singh, University of Florida, Department of Materials Science and Engineering, Gainesville, FL.
Lanthanum manganites have been the subject of renewed interest due to the large change in electrical resistance near their ferromagnetic ordering temperature in the presence of a magnetic field. Most of the colossal magnetoresistance (CMR) measurements on these systems, till date, have been carried out in a magnetic field around 6-7 Tesla at low temperature. However, since magnetic recording devices work at room temperature with low magnetic fields, the temperature range and field sensitivity of the manganites in their present state do not make them competitive to conventional giant magnetostrictive materials. In the present investigation, we have tried to modify the magnetoresistance properties of the La-Ca-Mn-O system by engineering their grain size to nano-scale in order to drastically increase the surface-to-bulk ratio. The nano-structured coatings of La-Ca-Mn-O on 10 micron alumina particles were obtained using laser assisted atomic flux coating (AFCP) process. The details of the experimental parameters of the AFCP process influencing the coating characteristics will also be presented.
CANTILEVER MOTION IN NON-CONTACT SCANNING FORCE MICROSCOPY. Fredy R. Zypman, Juan C. Merced, Idalia Ramos, University of Puerto Rico, PR; Carlos Negreira, Ramon Caraballo, Universidad de la Republica Oriental del Uruguay, URUGUAY.
In the study of soft samples with scanning force microscopy (SFM), and in order to avoid damage, it is necessary to reduce the tip-sample interaction force. This is usually achieved by working in attractive mode. To avoid loosing sensitivity under those conditions one could use a flimsier cantilever which is more likely than a sturdy one of hosting higher frequencies vibrational modes. We experimentally study the vibrations of a cantilever for typical SFM situations. We are able to measure resonance frequencies and also vibrational modes' shapes with a resolution of less than one percent of the cantilever total length. We will describe the measurement set up and the jumping between modes as the tip-sample distance changes.
ENERGY FILTERED IMAGING OF C60 THIN FILMS USING ELECTRON ENERGY-LOSS SPECTROMETER IN THE SCANNING TRANSMISSION ELECTRON MICROSCOPE. Dong Hyuk Shin, Dongguk University, Department of Physics, Seoul, KOREA.
Electron energy-loss spectra and energy filtered images have been obtained from amorphous C50 films deposited on Si(100) substrates using a serial EELS spectrometer equipped on a UHV field emission STEM. The EELS spectrum of the specimen in the low loss region reveals the plasmon energies of C50 to be 6.6eV and 25.3eV, which are similar to the plasmon energies of graphite. Energy filtered images have been obtains at energy-losses corresponding to images have been obtained at energy-losses corresponding to zero-loss, plasmon energies of Si and C50, and core loss energies of Si and C50. Energy filtered images can be obtained with reasonable signal intensity at energy-losses as high as 284eV. Contrast enhancement and elemental mapping depending on the choice of energy window are clearly observed. Energy filtered selected area diffraction (SAD) pattern indicates that the C50 film is amorphous with a mean intermolecular spacing of 7.1.
MICROSTRUCTURAL CHARACTERIZATION OF DIAMOND AND B-C-N FILMS PREPARED BY HOT-FILAMENT ASSISTED CHEMICAL VAPOR DEPOSITION. Max V. Sidorov, Center for Solid State Science, Arizona State University, Tempe, AZ; Zhiyong Y. Xie, J.H. Edgar, Department of Chemical Engineering, Kansas State University, Manhattan, KS; T.L. McCormick, Geo-Center, Fort Washington, MD.
Hot-filament chemical vapor deposition technique was used in an attempt to produce a diamond - cubic boron nitride alloy. The resulting films were examined by analytical transmission electron microscopy. The films were grown on Si substrates from mixtures of methane, hydrogen, diborane, and ammonia with gas input ratios of up to B/C=0.1 and N/C=0.5. For high B/C ratios, phase separation into individual faceted diamond crystallites, about 5 um in diameter, and a continuous matrix film occurred. A combination of high resolution TEM and EELS showed that the matrix film was a mixture of turbostratic h-BN and amorphous C. Cross-sectional TEM revealed that in some cases the diamond nucleated on top of the B-C-N matrix instead of the Si substrate. Neither boron nor nitrogen was detected in the diamond crystallites by EELS even for highest B/C and N/C ratios indicating very small solubility of these elements under our experimental conditions.
ELECTROPLATED CU(SN)-AL2O3/TALC COMPOSITES FOR APPLICATION AS WEAR RESISTANT MATERIALS. Yang Cao, Department of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec, CANADA; Yulin Wang, Naiqin Zhao, Shumei Zhao, Department of Materials Science and Engineering, Tianjin Uniersity, Tianjin, CHINA; J.A. Szpunar, Department of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec, CANADA.
A new electrodeposition method was proposed to form Al2O3/Talc-Cu(Sn) composites. The structure and wear resistance of the depositing composite were optimized by modifying the cathode current density, particle concentration in solution, speed of stirring, and plating time. These processing parameters strongly affects the volume of particles and the speed of deposition. The composite obtained as a result of this optimization has a wear resistance superior to that of Cu-Sn alloy and Cu-Sn-Zn-Pb alloy, respectively. The wearing rate of Al2O3-Cu(Sn) composites is affected by the load applied and the sliding speed. The optimum wear resistance is observed at low loads and sliding speeds. Talc-Cu(Sn) composites have a very low fiction coefficient compared to matrix alloy. That offers new possibilities to develop composites with properties of reduced wear and friction.
EFFECT OF LASER BEAM DIMENSION ON SUB-MICRON PARTICLES REMOVAL EFFICIENCY FROM SOLID SURFACES. S. Ivory D. Kumar, and Rajiv K. Singh, Department of Materials Science and Enginering, University of Florida, Gainesville, FL.
The presence of particles on the semiconductor surfaces is primarily responsible for reduced yields in the production of semiconductors devices through contamination of processes such as etching, photoresist striping and prediffusion cleaning. The magnitude of adhesive forces relative to the particle mass increases significantly for micrometer- and submicrometer-sized particles, and their removal is therefore very difficult. In this paper, we have examined the particulate removal efficiency of laser from solid surfaces. The results obtained have shown that line beam lasers can remove submicron particles more efficiently from solid surfaces. The mechanism responsible for higher particulate removal-efficiency of line beam laser has also been discussed. The use of line beam laser with better cleaning efficiency is very promising from the scale-up point of view as very large surface of the silicon wafer can be cleaned using very small laser energy density.
SESSION CC5: THICK FILMS AND PARTICLE BASED COATINGS
Chair: Helmut K. Schmidt
Tuesday Morning, December 2, 1997
Essex East (W)
8:30 AM *CC5.1
PARTICLE ASSISTED ENHANCED CHEMICAL VAPOR DEPOSITION OF DIAMOND FILMS. James H. Adair, Department of Materials Science and Engineering, University of Florida, Gainesville, FL.
Abstract Not Available
9:00 AM CC5.2
CERAMIC MULTILAYERS FROM NANOSIZED PARTICLES USING LASER TECHNOLOGY. J.Th.M. De Hosson, M. de Haas, G. Krol. D. van Agterveld, A. Vreeling, Department of Applied Physics, University of Groningen, Groningen, NETHERLANDS.
In collaboration with Philips (The Netherlands), Sandvik and MIT (Sweden), Pelikan (Switzerland), Fraunhofer Institute (Germany) we focus on the exploration of additive mass manufacturing of ceramic multilayers from nanosized ceramic particles using inkjet and laser technology. The basic idea is that a new additive technology generates a pattered layer with inkjet technology with ceramic materials dispersed in a water based colloidal sol of nanosized particles. The inkjet droplets are dried and sintered with a laser immediately after landing. The samples are fired by means of a CW-CO2 laser with a main wavelength of 10.6 m. A Galvo system was applied for quick movement of the laser-beam across the samples. Using a short laser pulse, the heat affected zone can be kept very thin (only one layer, order of 0.2 m), allowing high local sintering temperatures without damaging the product too much by heat. During the laser processing films are heated and cooled extremely rapidly, rather than in tens of seconds or minutes, as in conventional, furnace firing. In this paper the consequences for the densification mechanism are analyzed, both experimentally, using a special high resolution low voltage scanning electron microscope, and theoretically for various combinations of substrate and nanoceramic particle coating.
9:15 AM CC5.3
BARIUM TITANATE/EPOXY NANOCOMPOSITE COATINGS FOR INTEGRATED CAPACITOR APPLICATIONS. Shurong Liang and Emmanuel P. Giannelis, Cornell University, Dept of Materials Science and Engineering, Ithaca, NY.
The continuing trend of structural miniaturization in the microelectronics industry requires the integration of passive components such as capacitors into electronic packaging. Suitable dielectric materials and processes compatible with the existing packaging technology are being explored to fabricate thin film capacitors that can be incorporated into printed wiring boards. We have recently developed an approach to process barium titanate/epoxy nanocomposites that offer several advantages including ease of processing, low processing temperature, and versatility. In this process, nanocrystalline barium titanate particles are functionalized with a silane coupling agent, allowing the homogeneous dispersion of barium titanate particles into the epoxy matrix. Particulate coatings are formulated using silylated barium titanate particles, bisphenol A epoxy resin, dicyandiamine, and 2-methylimidazole in an organic solvent. Procedures have been devised to deposit nanocomposite thin layers on metallized substrates by spin- or dip-coating followed by curing at 150 ƒC. Thin layer capacitors have also been fabricated with low loss and capacitive density > 40 nF/cm2. Synthesis, processing, and structural as well as electrical characterization of these ceramic/polymer coatings will be presented.
9:30 AM CC5.4
DEVELOPMENT AND CHARACTERIZATION OF TITANIA FILMS BY FLAME ASSISTED AEROSOL COATING TECHNIQUES. Guixiang Yang and Pratim Biswas, Aerosol & Air Quality Research Lab, Dept of Civil & Environmental Engineering, University of Cincinnati, Cincinnati, OH; Punit Boolchand, Dept of Electrical and Computer Engineering, University of Cincinnati, Cincinnati, OH; Ashok Sabata, Armco, Inc, Middletown, OH.
Flame assisted aerosol coating processes were developed wherein titania films of different thickness were deposited onto stainless steel and silica substrates. The objective was to develop anti-corrosive ceramic coatings for steel to replace the current chromium based wet coating processes which pose serious environmental hazards . The flame deposited continuous (non-porous) titania films were examined by X-Ray Diffraction, Auger Electron Spectroscopy and Ar+ sputtering for its crystallinity and compositions as a function of its depth. The bonding between the ceramic oxide film and the substrates was also evaluated by the hardness, tensile strength and bending test followed by metallographic cross-section analysis using Scanning Electron Microscopy. The anti-corrosive characteristics were obtained by exposing the samples to marine atmospheres and using dc electrochemistry methods. Moreover, the developed titania films may have other fruitful technological applications such as for photocatalyst, solar energy conversion and electronic devices . Nanosize dependent characteristics were explored by Raman scattering and infrared spectroscopy. The nano scale modified quantum states were observed. Electron microscopy was used to identify the texture and microstructure of the films. Titanium precursor feeding rate and substrate deposition temperature were carefully controlled and efforts are made to establish the relationship of processing - structure - property of the titania films.
SESSION CC6: PARTICLE ADHESION AND CLEANING
Chair: Jorge L. Valdes
Tuesday Morning, December 2, 1997
Essex East (W)
10:15 AM *CC6.1
THE FORCES BETWEEN PARTICLES AND SURFACES IN CHEMICAL MECHANICAL POLISHING EXPERIMENTS. Michael T. Dugger, Sandia National Laboratories, Albuquerque, NM.
Abstract Not Available
10:45 AM *CC6.2
POST CMP CLEANING. Srini Raghavan, J.S. Jeon*, E.A. Kneer, Department of Materials Science and Engineering, University of Arizona, Tucson, AZ; *AMD, Sunnyvale, CA.
Abstract Not Available
11:15 AM *CC6.3
THEORETICAL MODELING FOR LASER CLEANING OF MICRO-PARTICLES FROM SOLID SURFACE. Y.F. Lu, W.D. Song, M.H. Hong, D.S.H. Chan, T.S. Low, Department of Electrical Engineering and Data Storage Institute, National University of Singapore, SINGAPORE.
Laser cleaning is an effective cleaning technique for removing particles from solid surfaces without damage. Taking Van der Waals force and cleaning force due to fast thermal expansion of substrates or particles induced by pulsed laser irradiation into account, a cleaning model was established for removal of particles from substrate surfaces. This model can be used to explain the influence of incident direction, wavelength, fluence and particle size on cleaning efficiency, and to predict the cleaning threshold fluence required for removing various particles from different substrate surfaces. The experimental results show that the laser cleaning efficiency increases with increasing fluence and pulse number, but does not depend on repetition rate. Laser irradiation from reverse-side of the substrate is more effective to remove particles than that from front-side. The experimental results are in good agreement with the theoretical analysis. This model has been used to provide parameter windows for industrial applications of the laser cleaning technique.
11:45 AM CC6.4
PAINT ADHESION OF METALLOCENE PLASTOMER BASED THERMOPLASTIC OLEFINS USED IN THE AUTOMOTIVE INDUSTRY. Michelle Mikulec, Ford Motor Company, Automotive Product Operations, Dearborn, MI; Thomas C. Yu, Exxon Chemical Company, Polyethylene Technology, Baytown, TX.
Metallocene plastomers are a new generation of impact modifiers for polypropylenes. The paint adhesion of two different types of metallocene plastomers as well as tow different types of ethylene-propylene rubbers were conducted in a benchmark composition. A new tribology test, the Ford STATRAM distinguished the ethylene butene metallocene plastomer as bring superior paint adhesion to all other plastomers and elastomers. A two level factorial design using the test parameters of a STATRAM was conducted to model the energy required to slide a rigid counterface along to adequately described test results. Much more complex polynomial models were required to model other sample due to the occurrence of many catastrophic failures (excessive paint loss) during the experiment. Low voltage scanning electron microscopy was utilized to investigate the painted samples near the TPO surface. The ethylene-butene plastomer displayed extremely fine dispersion near the TPO surface compared to other three modifiers evaluated, hence its superior paint adhesion.