Papers

ICMCTF2006 Session DP: DP Poster

Thursday, May 4, 2006 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2006 Schedule

DP-1 Immobilization of TiO₂ Nanoparticles on Fe-Filled Carbon Nanocapsules for Photocatalytic Applications H.C. Huang (National Tsing Hua University, Taiwan); G.L. Huang (Union Chemical Laboratories, Taiwan); H.L. Chen, Y.-D. Lee (National Tsing Hua University, Taiwan) In this work, TiO₂ nanoparticles were immobilized on Fe-filled carbon nanocapsules (CNC) via a sol-gel reaction at room temperature. The high-resolution TEM images of the TiO₂-containing Fe-filled CNC indicated that the growth mechanisms of TiO₂ immobilization onto hollow and metal-filled CNC were different. The TiO₂ nanoparticles immobilized on both kinds of CNC were spherical anatase nanocrystals with diameter smaller than 6 nm. The effects of using TiO₂ immobilized on Fe-filled CNC to remove nitrogen oxide (NO) by gaseous NO oxidation had been investigated and were also compared with those of free TiO₂ and Fe-filled CNC only. Due to the simple and mild reaction condition, we could provide these photocatalysts, such as TiO₂, with a magnetic carrier, which numerous magnetic metals, such as iron, cobalt and nickel, were filled in CNC by an arc method, thereby leading to various potential nanotechnological applications.
DP-2 Influence of Metal Plasma Ion Implantation on Photo-Catalysis Sensitivity of Anatase TiO₂ Thin Films D.-Y. Wang, H.-C. Lin, C.-C. Yan (Mingdao University, Taiwan) Nanometric TiO₂ coatings were synthesized by using sol-gel and spin-coating technique on glass substrates for anti-bacterial applications. After atmospheric calcinations at 500°C, uniform TiO₂ coatings with pure anatase phase, showing positive photo-catalysis behavior, were successfully deposited. To further enhance the photo-catalysis sensitivity of TiO₂ thin films for using under visible light irradiation, a metal plasma ion implantation process was developed. A series of band-gap metal atoms such as Ni, Cu, V, and Fe were ionized and accelerated at 20 KV and impinged on the surface of TiO₂ coatings at a dosage of 5 x 1015 ions/cm². Among all tested implant materials, Cu and Fe ions demonstrated a significant ban- gap energy reduction from 3.2 to 2.2 eV, allowing efficient photo catalysis reaction to proceed in visible light environments. The feasibility of the ion-implanted TiO₂ thin films for using under visible light irradiation was demonstrated with contact-angle measurements and anti-bacterial drop tests against the E. Coli.
DP-3 Characteristics of CNTs Based-Stainless Steel Electrode for Electric Double-Layer Capacitor Application T.C Hung (National Chiao Tung University, Taiwan) Carbon nanotubes were synthesized from methane and hydrogen gas mixture directly on stainless steel plate by microwave chemical vapor deposition system. Prior to CNTs growth, the usual cleaning with organic solvent ethanol, acetone and hydrogen plasma pretreatment upon the substrate were necessary to be treated. Synthesized CNTs were curly in shape, and proper pretreatment of the substrate surface was required for the satisfactory growth of CNTs. It was deserved to be mentioned that CNTs cannot be successfully synthesized on the substrate without the foregoing procedure. The as-received CNTs were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectrum apparatus. Carbon nanotubes could be fabricated into electrodes, face to face, for EDLC without any further treatment. Finally, with an electrolyte composed of GBL ion solution, cyclic voltammetry and charge/discharge results showed specific capacitance about 100 F/g.
DP-4 New Approach in Depositing Thick Cubic Boron Nitride Coatings by Oxygen Addition - Structural and Compositional Analysis M. Lattemann (Linköping University, Switzerland); J. Ye, S. Ulrich (Forschungszentrum Karlsruhe, Germany) Cubic boron nitride (c-BN) can be produced by PVD and CVD techniques by intensive high energy ion bombardment leading to highly stressed films limiting its use in industrial applications. Various attempts have been undertaken to reduce the compressive stress of c-BN thin films. A significant reduction in the compressive stress and a substantially improved adhesion was achieved by a new coating concept consisting of an adhesion-promoting boron-rich base layer, a compositional-graded nucleation layer obtained by a stepwise increase of the nitrogen content in the Ar/O₂ atmosphere, and an low-stressed c-BN top layer with controlled oxygen addition. The 2.55 µm thick three-layered c-BN film was deposited by unbalanced radio frequency magnetron sputtering of a hot-pressed hexagonal boron nitride target on silicon substrates and hard metal inserts. The adhesion layer was deposited in a mixed Ar/O₂ atmosphere of 0.26 Pa with a stepwise increased ion energy by increasing the substrate bias from 0 to -350 V. The oxygen content in the gas flow was kept constant at 1%. The present study was focused on the investigation of the nanostructure, the nanoscaled chemical composition, and the chemical bonding structure using high-resolution transmission electron microscopy (HRTEM), analytical scanning transmission electron microscopy (ASTEM) and X-ray photoelectron spectroscopy (XPS). The HRTEM images revealed a nanocrystalline c-BN top layer which started to nucleate on the (0002)-oriented turbostratic BN nucleation layer when the stoichiometric composition was achieved. The overall oxygen content was determined to be about 5%.
DP-5 Characterization of Magnetron co-Sputtered W-doped C-based Films C.W. Moura e Silva, J.R.T. Branco (REDEMAT / CETEC, Brazil); A. Cavaleiro (ICEMS - University of Coimbra, Portugal) DLC (Diamond-like Carbon) coatings have high hardness and low friction coefficient with great potential to act as self-lubricant layers, envisaging a vast range of environmental and tribological benefits. In last years DLC coatings have had an ever-increasing number of applications in many different fields of industrial activities. However, these layers have high residual stress, which may impair their use, particularly when the mechanical components are submitted to strong loading. Among the different solutions to minimize this limitation, metal doping is an alternative recently proposed. In this paper, DLC films doped with tungsten (DLC-W) were deposited on steel substrates by rf magnetron sputtering, using W and C targets, varying either the deposition power in both targets and the substrate bias. The substrates were placed in a row from the C to W targets in order that the chemical composition could be varied. The films were characterized concerning their chemical composition, structure, morphology, hardness and adhesion. Both the effect of the W contents incorporated in the DLC film and the influence of deposition parameters on the properties of films were investigated. As it would be expected the W contents in the films increased from 1-2at.% over the C target until 60at.% in the coatings deposited onto the substrates over the W target. The coatings showed amorphous structures excepting those having W contents higher than 19at.% for which the formation of WC_1-x structure could be detected. C-rich DLC films are very dense which progressively changed to a type T and, finally, to a columnar type 1 morphologies with increasing W contents. Amorphous films have hardness in the range from 10 to 14GPa whereas values as high as 20GPa can be reached in crystalline ones. The low values of adhesion (Rockwell indentation) suggested that an adhesion interlayer is needed for improving the adhesion between the films and the substrate.
DP-6 Effects of Deposition and Post-Annealing Conditions on Electrical Properties and Thermal Stability of TiAlN Films by Ion Beam Sputter Deposition S.-Y. Lee, J.-L. Huang, J.-S. Chen (National Cheng-Kung University, Taiwan); S.-C. Wang (Southern Taiwan University of Technology, Taiwan) TiAlN films were prepared by ion beam sputter deposition using a Ti-Al (90/10) alloy target in nitrogen atmosphere on thermal oxidized Si wafers. Effects of substrate temperature and post annealing sequences on electrical properties and thermal stability of TiAlN films were studied. XRD and resistivity measurement results reveal that TiAlN films deposited at lower substrate temperature(Ts) shows better crystallinity and are more stable than films deposited at higher Ts. Films deposited at Ts=50°C show low resistivity around 300micron ohmcm even post annealed at 600°C in oxygen and the XRD pattern shows minor oxidization of the films. On the other hand, films deposited at Ts=250°C oxidized obviously after 600°C post annealing in oxygen and shows much higher resistivity of 1700micron ohmcm. The relation of electrical property and thermal stability with films composition were also discussed in this paper.
DP-7 Effect of Gas Mixing on the Synthesis and Physical Properties of Sputtered nc-C Films S. Kim, H.S. Myung, Y.-M. Kim, Y.S. Park, B. Hong, J.-G. Han (Sungkyunkwan University, Korea) Since first synthesized by Aisenberg and Chabot in 1971, there has been a continuous growth on the study of synthesis and properties of carbon based films for a period of two decades. These films have various industrial applications due to attractive properties such as high hardness, low friction coefficient, high infrared transparency, high electrical resistivity, good chemical inertness and low surface roughness, etc [1-11]. In general, carbon based coatings prepared by plasma processing are described as an amorphic solid carbon composed of small sp² bonded graphitic clusters and sp³ coordinated carbon atoms. Therefore, high hardness of carbon based films usually linked with sp³ like bonds. However, sp²-dominated hard and conductive carbon based films are recently emerged [8-11]. These films have the advantage which various industrial applications are possible owing to hard and conductive properties and have been studied consequently so that it is achieve. In the present work, effect of gas mixing was particularly studied and the mechanism of film formation was proposed with variation of this parameter. Gas mixing ratio was varied from 0 to 80% at a fixed substrate bias voltage of -200V and a target power density of 30 W/cm². The aim of this study was to determine the relationship between the microstructure and physical properties of nc-C films as a function of the gas mixing ratio. The film structures were examined by Raman spectroscopy, x-ray photoelectron spectroscopy and field emission scanning electron microscopy. The physical properties of the nc-C films were evaluated using a nano indentation tester, a 4-point probe and a residual stress tester. The nc-C film deposited in gas mixing ration of 80% exhibited the minimum electrical resistivity.
DP-8 Purification Reaction Model of MWCNTs in High Efficiency Microwave-Digestion Purification Method C. Chen, Y. Yu (Minghsin University of Science and Technology, Taiwan); H. Hsu (National Chiao-Tung University, Taiwan) Although variety procedures were used to synthesize carbon nanotubes (CNTs), the as-prepared product still needs further modification to increase the purity of CNTs. Various acids have been used to remove metal catalysts. These processes involved repeated steps of filtering and long acid treatment time. However, CNTs nanotubes are cut into small length and even cause destruction. Walls of CNTs are always damaged by strong acid. In this research, Multi-walled carbon nanotubes (MWCNTs) synthesized by thermal chemical vapor deposition have been successfully purified by high efficient microwave-digestion purification method. Because that nitric acid in microwave digestion system can absorb energy quickly and dissolve metal particles efficiently, the amount of residual catalyst metals was eliminated from 10.39 wt % to 1.75 wt% within 10 min digestion time. After 120 min acid processing time, the amount residual metal in tube was less than 1.03 wt%. Then, adjusting the microwave digestion acid experimental condition, the reaction mechanism of dissolving metal catalyst within carbon nanotubes in acid solution was also investigated.
DP-9 Evaluation of DLC Interlayer in WC-Co Diamond Coated Tools on Cutting Performance of Dry Machining of Aluminium Alloys G. Cabral, P. Reis, P. Davim, N. Ali, J. Gracio (University of Aveiro, Portugal) In view of the range of applications of cemented tungsten carbide (WC-Co) for metal cutting, considerable research efforts are being made to produce diamond coatings on WC-Co material in order to improve tool performance in non ferrous materials such as aluminium alloys used in mould and automotive industries. In this investigation it is compared the tool life of commercial PCD and DLC coatings with CVD diamond (thickness lower than 8 m). The diamond films were deposited on commercial WC-Co as-ground substrates and in WC-Co with a DLC interlayer. The cutting performance of coated tool inserts were evaluated by tool life tests on 7122 aluminium alloy (AlZn₅Mg₃Cu). Cutting forces, tool wear, surface finish and dimensional accuracy of work piece were the criteria used to determine the cutting performance of coated tools. Scanning electron microscopy (SEM), and energy dispersion spectroscopy (EDS) were also used in order to analyse and reveal the dominant wear mechanisms occurred on coated tool inserts. Under the conditions used, it is report that diamond grain size is an important factor in governing tool wear and cutting performance.
DP-10 Low-Temperature CVD Growth of Carbon Nanotube for Field Emission Application C.-F. Chen, J.-H. Lee (National Chiao Tung University, Taiwan); C.-L. Hwang, Y.-Y. Chang (Industrial Technology Research Institute, Taiwan); K.-C. Chen (National Chiao Tung University, Taiwan) For field emission application carbon nanotube emitters were synthesized on the catalyst-mixed thick-film electrode lower than 500 cate) and conducting Ag powders were applied to fabricate the electrode by screen-printing process. These processes are simple, low-cost and easy to scale up for large sized panels. Both the diode and planar triode type were observed with uniform electron emission current and high brightness. The carbon nanotubes grown on Ni catalyst showed a multi-walled structure with defective graphenes. The turn-on voltage was about 3.8V/ µm with an emission current destiny of 10 microA/cm², and the threshold voltage was about 5.5V/ µm with an emission current destiny of 10mA/cm².
DP-11 Humidity Dependence of the Residual Compressive Stress of Diamond-Like Carbon Film Y.-J. Lee, K.-R. Lee (Korea Institute of Science and Technology, Korea) It is widely known that diamond-like carbon (DLC) film has significant instability in either humid or aqueous environment. The instability results in the failure of the DLC coating in humid operation condition. For example, tribo-test of the DLC coating in aqueous environment frequently showed an adhesive wear due to the delamination of the film in the wear track. For the biomedical application of the DLC coating where an extreme reliability of the coating is required, the instability is one of the major concerns. Two possible reasons for the instability would be addressed: increasing the residual compressive stress in humid environment or degradation of the film/substrate interface due to the water molecules from the environment. In this study, the humidity dependence of the residual stress was investigated by employing an in situ stress measurement method in a humidity control chamber. Various DLC films were prepared by r.f.-PACVD using benzene, methane or their mixtures with diluted silane as the precursor gases. In situ measurements of the residual stress were carried out as the relative humidity (R.H) was changed in the range from 10 to 90%. The residual stress of polymeric film increased as the humidity increased. The change occurred immediately and reversibly as the relative humidity varied. The change of the residual stress decreased as the film thickness increased, which implies that the change is not caused by the changes in bulk but the changes in surface or interface. However, the humidity dependence of the residual compressive stress was not observed in a DLC film of dense atomic structure or Si incorporated DLC films.
DP-12 Thermal Annealing Effect of Tetrahedral Amorphous Carbon Films Deposited by Filtered Vacuum Arc Y.-K. Lee (Seoul National University, Korea); K.-R. Lee (Korea Institute of Science and Technology, Korea); K.-H. Oh (Seoul National University, Korea) Thermal annealing of tetrahedral amorphous carbon (ta-C) film has been widely used to reduce its high level of compressive stress. In the present work, we investigated the changes in atomic bond structure and the mechanical properties caused by the thermal annealing. The ta-C films were prepared by filtered vacuum arc process. In order to obtain ta-C films of various atomic bond structures, negative bias voltage of the substrate were varied from 0 to 650V. In this range of the bias voltage, the residual stress of the film monotonically decreased from 5.7 to 1.3 GPa. The specimens were annealed in vacuum at 600°C using rapid thermal annealing (RTA) system. The residual stress of the annealed ta-C film changed in contrasting manner depending on the initial atomic bond structure or negative bias voltage applied to the substrate during deposition. At the lower bias voltage ranging from 0 to 150V, residual compressive stress of the film significantly decreased by the annealing. In contrast, the residual compressive stress increased by the thermal annealing when the applied negative bias voltage was larger than 150V. However, no significant change in the hardness was observed after the thermal annealing. This contrasting behavior will be discussed in terms of the changes in atomic bond structure analyzed by Raman and ESR spectroscopy.
DP-13 Effects of Catalyst Preparation on Structural and Field-Emissive Properties of Carbon Nanotubes C.K. Park, S.T. Hong, J.S. Park (Hanyang University, Korea) Carbon nanotube (CNT) has attracted a great attention because of its high aspect ratio, high chemical stability, and a wide range of potential applications including flat panel displays, point electron sources, and microwave power vacuum tubes. For application as a field electron emitter, the density and the dimension control of CNTs may strongly be affected by surface conditions of catalyst films. Moreover, in order to prevent silicide formation at elevated temperature, buffer layers between substrates and CNTs are required. However, there has scarcely been reported in literature regarding these issues. We present experimental results that regard the effects of catalyst preparation on the structural and field-emissive properties of CNTs. The CNTs used in this research have been synthesized using the inductively coupled plasma-chemical vapor deposition (ICP-CVD) method by varying dc electric biases applied to substrate electrodes. Various buffer materials such as TiN, Cu, and Pt/Ti are prepared on SiO₂-coated Si substrates by magnetron sputtering and patterned by photolithography to have 20 µm diameter disk cells. Catalyst materials (such as Ni, Co, and Invar 426) are also varied and deposited on buffer films by RF magnetron sputtering. Prior to growth of CNTs, NH₃ plasma etching has also been performed with varying plasma etching time and power. For all the CNTs grown, nanostructures and morphologies are analyzed using Raman spectroscopy, AFM, FESEM, and HRTEM, in terms of buffer films, catalyst materials, and pre-treatment conditions. Furthermore, the field electron-emission of CNTs are measured and characterized in terms of the catalyst preparation environments. The quantitative data regarding the dependence of the structural properties (such as length, diameter, and density) as well as the field-emissive properties (such as threshold field, maximum current density, and field-enhancement factor) of CNTs grown are presented in detail.
DP-14 Evaluation of Leukocyte Adhesion on Fluorinated Diamond-Like Carbon (F-DLC) Films T. Yoshimura (Keio University, Japan); T. Hasebe (Tachikawa Hospital, Japan); S. Yohena, T. Ishimaru, Y. Yoshimoto, T. Saito, A. Hotta (Keio University, Japan); A. Kamijo, K. Takahashi (University of Tokyo Hospital, Japan); T. Suzuki (Keio University, Japan) Blood-contacting medical devices gained increasing importance in routine medical and surgical practice. Modern strategies in developing biomaterials for medical implantable devices, such as cardiovascular stents and catheters, artificial organs and pacemakers, aim to improve their blood compatibility. Although platelets and activation of the coagulation cascade play a central role in thrombosis, material-induced leukocyte activation may also play a role in material failure. Leukocyte adhesion to artificial surfaces is an important phenomenon in the evaluation of biomaterials since adhered leukocytes often are related to inflammatory response after implantation involving blood-material interactions. As a result of leukocyte adhesion, several reactions may be initiated, such as leukocyte spreading; formation of microthrombi through platelet-leukocyte interactions; release of leukocyte products that may give rise both to local and systemic vascular reactions; inflammatory responses that are leukocyte-dependent; and promotion of fibroblast proliferation. Recently, diamond-like carbon films (DLC) got a lot of attention for their antithrombogenic property. In our previous studies, we developed more antithrombogenic films by doping fluorine to DLC (F-DLC) than conventional DLC films. DLC and F-DLC films were synthesized from acetylene (C₂H₂) and/or hexafluoroethane (C₂F₆) using radio frequency (RF) plasma enhanced chemical vapor deposition (CVD) system. We have reported that F-DLC coating dramatically reduced the number of platelets, and also inhibited platelet activation. In this present study, we focused on the leukocyte adhesion and activation and evaluated the interaction of freshly isolated human leukocytes with DLC and F-DLC films deposited on polycarbonate (PC) substrates by scanning electron microscope observation.
DP-15 Electrochemical Corrosion Behavior of Carbon-Based Thin Films in Chloride Ions Containing Electrolytes G. Reisel (TU Freiberg, Germany); A. Dorner-Reisel (TU Bergakademie Freiberg, Germany); B. Wielage (TU Chemnitz, Germany) Hard carbon-based thin coatings with outstanding tribological resistance are used for several applications like the surface protection of cutting or forming tools [1], precision parts in medicine (heard valves, chirurgic instruments) [2,3] or automotive components (bearing rolls, camshafts, injections systems) [4]. In addition to wear, further loads, like corrosive attacks or fatigue do act during the operation of the components. Commercial available carbon-based thin films consisting of single layers of amorphous dia-mond-like carbon or multilayers of crystalline TiAlN or CrN with diamond-like carbon top coatings were evaluated in relation to their electrochemical corrosion behavior in chloride ions containing electrolytes. As a substrate material a working steel (0.9 % C, 4.1 % Cr, 4.9 % Mo, 1.8 % V, 6.4 % W) is used. The potentiodynamic corrosion behavior of coated samples were tested in 3.5wt.% NaCl solu-tion and in Hank's balanced body solution, HBBS (0.89wt.% NaCl, further chlorides, sulfates, carbonates and phosphates). The multilayers TiAlN + a-C:H:W and CrN + a-C:H:W effect a minor improvement of the corrosion resistance only. Single layers of amorphous diamond-like carbon coating without hydrogen (a-C) spell of during the corrosion tests in chloride con-taining media. A minor improvement of the corrosion resistance is reached. The hydrogen modified diamond-like carbon coatings a-C:H and a-C:H:Si showed the best corrosion resis-tance with a 100 times lower corrosion current density. [1] Reisel, G., S. Steinhauser, B. Wielage, Diamond Relat. Mater. 13 (2004) 1516 [2] Yu, L.J., X. Wang, H. Wang, H. Liu, Surf. Coat. Technol. 128-129 (2000) 484 [3] Grill, A., Diamond Relat. Mater. 12 (2003) 389 [4] Jungblut, F., S. Hessel, R. Ackermann, O. Wassler, in: EFDS e.V. Dresden (Hrsg.), Tagungs-band des Workshopsz Kohlenstoffschichten: Tribologische Eigenschaften und Verfahren zu ihrer Herstellungo, 25. Mai 2004, Dortmunder OberflachenCentrum.
DP-16 Knee Prostheses Wear Tests: Comparison of Femoral Parts with Hydrogenated Silicon or Nitrogen Modified DLC Coatings A. Dorner-Reisel (TU Bergakademie Freiberg, Germany); G. Reisel (TU Freiberg, Germany); L. Kuebler (CEWoTec GmbH, Germany); U. Kremling (IMA GmbH Dresden, Germany); E. Mueller (TU Bergakademie Freiberg, Germany) The loss of metallic or polymeric wear particles during the operation of artificial joints is a serious problem, which can lead to harmful pain of the patient. One measure to reduce the development of wear particles is the application of wear resistant coatings with outstanding adherence. The adherence and durability of coatings were problems, which stopped their application in artificial joints in recent times [1]. Also, some investigations report the failure of wear resistant coatings on components of artificial joints, but lack the consequent description of the coatings structure [2]. New approaches for using biocompatible and wear resistance carbon coatings are undertaken [3]. The results gives evi-dence that the wear of the polyethylene inlays can be reduced due to DLC coatings (DLC, diamond-like carbon) on the femoral components. In addition, the metallic release from the femoral part is pre-vented. The present study gives results from wear tests with DLC-coated femoral parts of knee joint prostheses. The used DLC coatings are hydrogenated diamond-like carbon coatings, which are struc-tural modified by additional elements like silicon and nitrogen. The prostheses were tested according the norm ISO 14 243 with a knee wear simulator "Stanmore KS4" up to 5 x 106 cycles. The nitrogen and silicon containing hydrogenated diamond-like carbon coatings reveal a further improved wear protection in comparison to the DLC coatings which are not modified by additional elements. The nano- and microstructure of the deposited DLC coatings is described in detail. Literature [1] Amstutz, H.C., P. Grigoris, Clinical Orthopaedics and Related Research, 329S (1996) S11 [2] Taeger, G., L.E. Podleska, B. Schmidt, M. Ziegler, D. Nast-Kolb, 5th International Essen Symposium on Biomaterials: Fundamentals and Clinical Applications, Conference Proceed-ings, 2002, 63 [3] A. Dorner-Reisel, C. Scherer, E. Mueller, Diamond Relat. Mater. 13 (2004) 823.
DP-18 Tailored CVD-Diamond Coatings for Highly Demanding Cutting Operations O. Lemmer, R. Cremer, D. Breidt (CemeCon AG, Germany) Continuously rising demands on efficiency and productivity of cutting operations e.g. high speed and high performance cutting and an increasing amount of composite materials to be machined require on the one hand a general view of the cutting process, workpiece and tool as a uniform process and the need to tailor the coated tool's properties exactly to the specific application. Especially fibre reinforced materials can not be machined with conventional tools, but also other high-tech materials e.g. green compacts, non ferrous alloys, intermetallics, printed circuit boards (PCB) and extremely abrasive Al-Si and Ti-Al alloys require tailored diamond coated tools for reasonable machining operations. All these demands can be met by well to the Co-content adjusted pre-treatment of the cemented carbide tools to guarantee a perfect adhesion and improved interface. Furthermore the morphology of the diamond coatings can be exactly controlled leading to micro- and nano-crystalline as well as multilayered coatings to increase fracture toughness. It is even possible to sharpen diamond cutting edges for machining of wood or chipboards. All possible treatments and processes may be used solely or combined to produce the ideal fitted diamond coated tool for specific application to achieve an optimum performance in cutting operations at reasonable costs. This will be illustrated by selected cutting test results in most demanding applications.
DP-19 Study of Reactively Sputtered GaAs_xN_1-x Thin Films B.S. Yadav, S.S. Major, R.S. Srinivasa (IIT Bombay, India) Thin films of GaAs_xN_1-x alloys were deposited by reactive rf magnetron sputtering of GaAs target using a mixture of nitrogen and argon as the sputtering atmosphere. Films were deposited on quartz substrate in the temperature range of 500 - 600°C, using different ratios of argon and nitrogen. The growth rate of the films was in the range of 1-2 µm/hr, and showed a gradual increase with increasing argon content of the sputtering atmosphere up to 95 %. At higher argon content of the sputtering atmosphere, the growth rate increased steeply to 7-8 µm/hr corresponding to 100 % argon. XRD and TEM studies showed that the films deposited with less than 92 % argon in the sputtering atmosphere were polycrystalline, single phase, hexagonal GaN. In contrast, the films deposited with more than 95 % argon in the sputtering atmosphere were found to be amorphous. Interestingly, the films deposited in a narrow range of 92 - 95 % argon (5-8 % nitrogen) exhibited the structure of hexagonal GaN but showed a monotonic increase in lattice constants with increase in argon content of the sputtering atmosphere, which is attributed to the incorporation of As in GaN lattice. The formation of amorphous films above 95 % argon in the sputtering atmosphere is attributed to the difficulty of substituting larger arsenic atoms in the nitrogen sites of GaN lattice. The optical absorption of the films was obtained from reflection and transmission data in the photon energy range of 1.5 to 4.5 eV. The plots of α² vs. hν showed a continuous decrease in the absorption edge from 3.4 (corresponding to pure GaN) to 2.2 eV with increase in arsenic content, corresponding to the increase in argon from 92 - 95 % in the sputtering atmosphere. The optical results corroborate well with the structural data, thus confirming the formation of GaAs_xN_1-x alloy films by this novel approach.
DP-21 Atmospheric Dielectric Barrier Discharge Functionalization of Chemically Activated MWCNTS T.I.T. Okpalugo, P. Papakonstantinou, N.M.D. Brown, P.D. Maguire (University of Ulster, United Kingdom) Functional groups can be introduced onto nanotube surfaces by conventional solution processing, thermal treatment or vacuum techniques. In view of applications requiring prefabrication of aligned CNT for highly sensitive bio-sensing, we have developed a non-vigorous, quick and cheap atmospheric pressure dielectric barrier discharge (DBD) process for purifying and attaching specified molecular groups to carbon nanotubes without involving the use of wet chemicals, high temperatures and high vacuum. Functionalization of MWCNTs with O, N, Cl and F groups using ordinary air, ammonia or trichlorotrifluoroethane vapours has been demonstrated. The attachment and bonding of the added functional groups have also been verified by various techniques. Detailed XPS, Raman, TGA and XANES analysis was used to determine the resultant bonding configurations. The MWCNTs were initially treated in HCl to remove the metal growth catalyst and subsequently were subjected to a chemical activation route involving reflux in HNO₃. The chemically activated MWCNTs after treatment in DBD-NH₃ atmosphere attracted four times (x4) more N atoms compared to their non-activated counterparts. In contrast, the non-chemically activated MWCNTs after treatment in trichlorotrifluoroethane-DBD atmosphere, attracted eight times (x8) more F and three times more (~3x) Cl atoms, when compared to their chemically activated counterparts. The results are explained in terms of the electron capturing nature of the functional groups and the preoccupation of the bonded and non-bonded reactive sites on the CNT surfaces.
DP-23 Determination of the Hydrogen Content in Diamond-Like Carbon and Polymeric Thin Films by Reflection Electron Energy Loss Spectroscopy F. Yubero, V. Rico, J.P. Espinos, J. Cotrino, A.R. Gonzalez-Elipe (Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla), Spain); D. Garg (Air Products and Chemicals) A new non-destructive method to determine hydrogen content in diamond-like carbon and polymeric thin film materials is developed. The method relies on quantification of the intensity of elastic peak stemming from the backscattering of electrons with the hydrogen atoms present in the samples as measured by reflection electron energy loss spectroscopy. Quantitative analysis of the hydrogen content at the surface of diamond like carbon thin films is achieved by using phenomenological sensitivity factors of hydrogen against the other atoms with reference to polymeric samples. The validity of the method is checked with elastic recoil detection measurements. A comparison is also made with data provided by infrared spectroscopy analysis of the same samples. We estimate that the error bar in the determination of hydrogen content in the samples is around 20% of the total hydrogen content.
DP-24 Study on Metal-Doped Diamond-Like Carbon Films Synthesized by Filter-Arc Deposition Process K.-W. Weng (Mingdao University, Taiwan); S. Han (National Taichung Institute of Technology, Taiwan); Y.-C. Chen (National Chung Hsing University, Taiwan); D.-Y. Wang (Mingdao University, Taiwan); H.-C. Shih (National Tsing Hua University, Taiwan) Diamond-like carbon (DLC) and diamond film have similar characteristics and being controlled easily in its preparing environment. Commonly used deposition methods for DLC are ion beam assisted deposition (IBAD), sputter deposition, plasma enhanced chemical vapor deposition (PECVD) and cathodic arc evaporation (CAE). The first two methods are limited to lower plasma ionization rate to cause lower sp³/sp² bonding and to cause low hardness of the DLC. The property of PECVD and CAE deposited films could be degraded by the presence of particles. In this research with filter arc deposition (FAD) technology is used to prepare DLC film with low particle number density. By applying plasma filter magnetic field intensity up to 100% and preventing particles deposited. CrN interface between the substrate and DLC film and increasing thin film adhesion are expected to get dense DLC film of with smooth surface and excellent mechanical property, film adhesion, in particular. Substrates bias and target current as parameters were varied to investigate its influence on microstructure, surface morphology and mechanical characteristics. Experimental results show that FAD-DLC film has less ID/IG ratio, which implies. The high sp³ bonding contained in DLC film compared with the CAE-DLC. Particles number density on FAD-DLC is half less than that of CAE-DLC. The proposed CrN interface between substrate and of DLC film and properly controlling of magnetic field strength of the filter will obviously improve DLC deposition in contrast to the traditional CAE process which normally encounters the adhesion failure and particles contamination.
DP-26 Luminescence Properties of Wurtzite AlN Nanotips C.-F. Chen, S.-C. Shi (National Chiao Tung University, Taiwan); K.-H. Chen (Academia Sinica, Taiwan); L.-C. Chen (Taiwan University, Taiwan) The optical properties of wurtzite AlN nanotips (AlNNTs) synthesized via vapor transport condensation process on silicon substrates coated with a metal layer are studied by cathodoluminescence (CL), photoluminescence (PL), thermoluminescence (TL), and UV absorption. CL measurement showed two defect related transitions around 2.1 and 3.4 eV and a well resolved excitonic feature at 6.2 eV. Two broad peaks centered at 2.1 and 3.4 eV were also observed from the PL and TL spectra. Analysis of the excitation spectra of both PL and TL measurements suggested the existence of multifold energy levels within the gap. This is also confirmed by the optical absorption spectrum. Basing on the experimental results it is assumed that several different energy transfer mechanisms occur in AlN.

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