ICMCTF2008 Session DP: Symposium D Poster Session

Thursday, May 1, 2008 5:00 PM in Room Town & Country
Thursday Afternoon

Time Period ThP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2008 Schedule

DP-1 Low-Stress, Adherent Cubic Boron Nitride Films with Oxygen Addition
J. Ye, S. Ulrich, C. Ziebert (Forschungszentrum Karlsruhe, IMF I, Germany)
Well-adhered, low-stress cubic boron nitride (c-BN) films were successfully grown on to silicon substrates by means of controlled addition of oxygen into the films. The deposition was based on the radio-frequency magnetron sputtering of a hexagonal boron nitride (h-BN) target, and was accomplished in a reactive mode using gas mixtures of argon/nitrogen/oxygen at 0.3 Pa pressure, 400°C growth temperature, and -250 V substrate bias. In the present study, systematic results are shown with respect to the critical influences of oxygen partial pressure during deposition upon the stress, cubic phase fraction, as well as nanohardness of the deposited films. Although the formation of c-BN was completely hindered at oxygen fractions above 1.5 vol.% in the gas mixture, there existed only marginal influences on the c-BN fraction, yet strong impact on the film stress on the other hand, when limiting the oxygen content within 1 vol.%. Cubic-phase dominated films (containing 70~80 vol.% c-BN) with their compressive stress three times reduced were thus produced through careful control of oxygen partial pressure, showing an excellent plastic hardness of almost 60 GPa. For such films, a post-deposition thermal treatment at 900°C was found to bring about an additional drastic stress relaxation leading to an ultimate stress that is almost 10 times lower than that of as-deposited c-BN films without intentional oxygen addition. Furthermore, owing to the reduced film stress, adherent, µm-thick c-BN films were achieved, with an adequate buffer layer, on to silicon substrates.
DP-3 Size and Temperature Dependent Surface CO Stretching Frequency Investigation on Nanodiamonds
C.D. Chu, J.S. Tu, E. Perevedentseva, C.L. Cheng (National Dong Hwa University, Taiwan)
Nanometer-sized diamond has been identified to be an ideal nanoparticle for bio applications. It can be easily conjugated with interested biomolecules; and the functionality of the conjugated biomolecules can be preserved. In this study, the spectroscopic properties of surface functionalized and bio-conjugated nanodiamond were investigated via Fourier Transform Infrared Spectroscopy (FTIR). The creating of molecular functional groups on nanodiamond surface was achieved chemically using strong acid treatment. Surface functional groups (e.g. COOH) are created on the nanodiamond surface. The surface C=O stretching frequency was studied for particle’s sizes from 5 nm to 500 nm. This frequency is ~1820 cm-1 for particle size 500 nm, and down shifts to 1725 cm-1 with decreasing particle size to 5 nm as a result of hydrogen bonds formation between the COOH groups in the particles surface; and the C=O stretching is strongly size-dependent. In the temperature-dependent investigation, it was found C=O stretching is also temperature-dependent. The observed red-shift on the C=O stretching for 100 nm diameter nanodiamond from 1816 cm-1 to 1804 cm-1 when temperature increased from room temperature to 600°C was attributed to water desorption and the dephasing of CO stretching with diamond bulk phonons. This work provides understanding of nanodiamond surface properties and the spectroscopic properties of the nanodiamond-biomolecule complexes.
DP-4 High Quality Nanocrystalline Diamond Films Grown by Down-Flow Microwave Plasma-Assisted Chemical Vapor Deposition
H. Gamo (Toppan Printing Co. Ltd., Japan); K. Shimada, T. Shibasaki (Toyo University, Japan); T. Ando (National Institute for Materials Science (NIMS), Japan); N.M. Gamo (Toyo University, Japan)
Nanocrystalline diamond growth has been extensively studied for future applications. In order to form diamond nanocrystallites, many studies have been performed to introduce defects into diamond structure. For introducing defects, high-energy ions are used to impact the growth surface by applying dc bias voltage to the surface in the plasma. Contrary to this, our growth method focused to realize a damage-free growth process suitable for high-quality crystal growth. We used tubular-type microwave plasma-assisted chemical vapor deposition reactor. In this system, the substrate position was apart from the plasma during the growth in the quartz reactor. The down stream position is expected to prevent the growth surface from being damaged by ion bombardments and electron irradiation from the plasma. In this experiment, the down-flow position of the Si substrate was varied in the range from 5 mm to 105 mm apart from the edge of the microwave plasma. 10 % methane diluted with hydrogen was used as a reactant gas and the total flow rate was 20 sccm. The gas pressure was 5 Torr and the incident microwave power was 300 W. Transmission electron microscopic observation was revealed that the fine structure of the grown films varied with the down-flow positions. Polycrystalline diamond films were grown in the down-flow positions in the range from the position at the edge to that of 45 mm apart from the edge. In the down-flow positions of 45-65 mm apart from the edge, high quality nanocrystalline diamonds could be obtained. The size of the nanocystallites was approximately 3-10 nm and amorphous phase were hardly observed at the interface of these nanocrystallites.
DP-5 High-Resolution Electron Microscopic Observation at the Interface Between the Diamond-Supported Metal Catalysts and the Carbon Nanomaterials Produced from the Metal-Catalyzed Decomposition of Lower Hydrocarbons
M. Nishitani-Gamo, K. Nakagawa, M. Kikuchi, Y. Hatanaka (Toyo University, Japan); H. Gamo (Toppan Printing Co. Ltd., Japan); T. Ando (National Institute for Materials Science (NIMS), Japan)
We have recently reported the oxidized diamond presents an excellent support material for catalysts (Chem Lett. (2000) 1100.). High yields of hydrogen and fibrous carbon nanomaterials can be obtained by the decomposition of methane using oxidized diamond-supported Ni and Pd catalysts (Chem Mater 15. (2003) 4571.). The grown fibrous carbon nanomaterials covered the diamond: this sphere-like material is considered to be a composite of sp3 carbons and sp2 carbons. The structure makes it attractive a unique carbon which is expected to yield various properties. In this study, we observed the interfacial structure of the diamond-supported metal catalysts and the carbon nanomaterials by using a transmission electron microscopy (TEM) to know what occurred at the initial stage of the solid carbon deposition. We used the oxidized diamond as the catalyst support. Catalysts were prepared by impregnating an aqueous solution of Ni nitrate or Pd acetate. The decomposition of lower hydrocarbons over oxidized diamond-supported catalysts was carried out using a fixed-bed flow-type quartz reactor at atmospheric pressure. The structural details of the fibrous carbon nanomaterials and the interfacial region were obtained from TEM studies. In the case of using Ni as a catalyst, the Ni particle was mainly found at the tip of the fibrous nanomaterial, but not found at the interface between the diamond and the nanomaterial. In the case of Pd, the Pd particles were found on the diamond support surface, and were covered with the solid carbon deposits. With increase of the reaction time, the fibrous carbon nanomaterials started growing from the both sides of the encapsuled Pd particle.
DP-6 Direct Growth of Carbon Nanotubes on a Micro-Sized Cobalt Tip and Characterization of Electron-Emission Properties
J.P. Kim, Y.K. Kim, C.K. Park (Hanyang University, Korea); H.Y. Choi, J.U. Kim (Electro-Fusion Technology Research Div., KERI, Korea); J.S. Park (Hanyang University, Korea)
In high-resolution x-ray tube application, carbon nanotubes (CNTs) offer several advantages such as excellent electron emission, low threshold voltage, micro-focusing, and enhanced current stability. To realize a micro-focused x-ray tube using a CNTs-based cold cathode, the emittance of electron beam should be decreased as small as possible. For this reason, substrates having a conical shape with a few hundreds of micrometer in diameter have usually been used by coating catalyst metals. This manner, however, may cause several inherent problems, such as poor adhesion between CNTs and substrates, large contact resistance, and technical difficulty of growing CNTs directly on such tip-type substrates. In this study, we suggest for the first time a novel method for direct growth of CNTs on various micro-tip materials, such as nickel (Ni), cobalt (Co), and iron (Fe), without using any other catalyst layers and present experimental results regarding to their electron emission properties. CNTs are grown by inductively coupled plasma-chemical vapor deposition (ICP-CVD). Sharpening of metal-tips is done by electro-chemically etching the metal-wires with diameter of 250 µm in a KCl solution by applying dc voltage between the metal-wire and the platinum (Pt) electrode. The metal-tips are exposed to NH3 plasma prior to growth of CNTs. For all the grown CNTs, Raman spectroscopy, field emission SEM, and high-resolution TEM are used to analyze their structural properties. Electron-emission currents have been measured using a compactly designed field-emission measurement system. The long-term stability of emission currents are discussed in terms of the micro-tip metals used.
DP-7 Tribological and Corrosion Properties of DLC Films Deposited by Laser Induced High Current Pulsed Arc Deposition
J.-B. Wu, Z.-Y. Chen (Material and Chemical Research Laboratories, Industrial Technology Research Institute, Taiwan); M. Li (National Nano Device Laboratories, Taiwan); C.-T. Shin, M.-S. Leu, A.-K. Li (Material and Chemical Research Laboratories, Industrial Technology Research Institute, Taiwan)
Diamond-like carbon (DLC) coatings have been deposited on Si(100) and stainless steel substrates by laser induced high current pulsed arc (LIHCPA) system. Adherent deposits on substrates can be obtained through applying gradient Ti/TiC/DLC layers. A pulsed current more than 1 kA was generated on the target in order to make DLC coatings have higher hardness and denser structure. The microstructure and hardness value of DLC films were analyzed by using X-ray photoelectron spectroscopy and nanoindenter. The experimental results show that the arc current had strong influence on the hardness and sp3 content of the DLC coatings. It has been observed that when the arc current was raised from 1 kA to 4 kA, the sp3 fraction of the DLC films measured by XPS increased from 47 % to 61 % accordingly. The corrosion behavior of DLC coatings was also studied in 0.5 M H2SO4 solution by using potentiodynamic polarization method. These results showed that DLC coatings on stainless steel exhibited excellent corrosion behavior especially in lower corrosion current which was less than 4x10-7 A/cm2.
DP-8 Deposition of Wide Band Gap DLC Films Using R.F. PECVD
P.K. Barhai, R. Sharma, S. Chattopadhyay (Birla Institute of Technology, India); B.B. Nayak (Regional Research Laboratory, India)
Diamond-like carbon films (DLCs) are deposited on silicon (100) substrates using capacitive coupled R.F. PECVD at room temperature. The deposition of films is carried out at a constant pressure (~ 5 ´10-2 mbar) using acetylene precursor diluted with argon at constant R. F. power of 5W. Raman spectroscopy of deposited DLC films shows broad G peak near 1550 cm-1 and a negligible D peak near 1300 cm-1. FTIR data of DLC films show clear peaks near at 1687 cm-1, 1514 cm-1 and 1213 cm-1 and two very small peaks near 2900 cm-1 and 2800 cm-1. Hardness and modulus of the deposited film are found to be 7GPa and 100GPa respectively. Band Gap measurements show two steps in the range of UV and visible region corresponding to band gap ~4 ev and ~2 ev respectively. Surface morphology of the deposited film is also studied by atomic force microscope (AFM). sp2 and sp3 phases of the deposited DLC films are explain by subplantation model.
DP-9 Characterization of SP3-Rich Diamond-Like Carbon Film Synthesized by a Cathodic Arc Activated Deposition Process
W.C. Lin, D.-Y. Wang (Mingdao University, Taiwan)
Diamond-like carbon (DLC) films possess outstanding physical and chemical properties such as chemical inertness, extreme hardness, and other electrical and optical properties suitable for various advanced applications in modern industry. To ensure the service quality, the SP3/SP2 carbon bond ratio, as the key characteristic of DLC films, has to be regulated through a process control mechanism. In this study, an SP3-rich DLC film was synthesized by using a cathodic-arc activated deposition (CAAD) process. The unique process takes advantage of the cathodic arc plasma to trigger the chemical decomposition reaction for DLC synthesis. The energetic metal plasma catalyzed the decomposition of hydrocarbon gas (C2H2), and induced the formation of the metal doped and hydrogenated DLC films. The formation mechanism for SP3 in DLC were studied by ESCA and plasma diagnostic (Optical Emission Spectrometry, OES and langmuir probe). Tribological test, SEM and Raman spectroscopy were employed to characterize the microstructure and carbon bond properties of DLC coatings. As a result, a set of optimized synthesis parameters for high-SP3 DLC films could be obtained.
DP-10 Preparation of Si-Incorporated DLC Thin Film in T-Shape Filtered Arc Deposition System
M. Kamiya, H. Tanoue, T. Mashiki, H. Takikawa (Toyohashi University of Technology, Japan); M. Taki, Y. Hasegawa (Onward Ceramic Coating Co., Ltd., Japan); M. Kumagai (Kanagawa Industrial Technology Research Center, Japan)

Diamond-like carbon film incorporating silicon as well as hydrogen (DLC:Si:H) was prepared in T-shape filtered arc deposition system (T-FAD). Clean carbon plasma beam was extracted from the cathodic vacuum arc with graphite cathode by passing it through a T-shape droplet-filtering duct. Tetramethylsilane (TMS) vapor was introduced into the process chamber to incorporate Si in the film. Thus, the film was deposited physically by the cathodic carbon plasma and chemically by plasma enhanced CVD mechanism with TMS as the precursor source gas.

DLC:Si:H was then deposited at various process conditions, such as arc current, gas flow rate, process pressure, and substrate bias. These conditions were as follows. Cathode, graphite; arc current, 30 A or 50 A: TMS vapor flow rate, 5 to 40 sccm; process pressure, 0.05 to 0.2 Pa; substrate bias, pulse -100 V, 10 kHz, duty 20%. The substrate was super hard alloy (tungsten carbide with cobalt binder; WC). The substrate was not heated and the substrate temperature was less than 60°C. The deposition rate was obtained from the film thickness. The film was analyzed by micro-Raman spectroscopy, X-ray diffractometry (XRD), and stylus surface profiler and optical reflectometry. Raman spectroscopy and XRD revealed that the film was amorphous. The G-band peak in Raman spectra was found to shift to the lower wavenumber and the deposition rate increased as increasing the flow rate.

DP-11 Preparation and Properties of Amorphous Carbon Films on PEEK (Poly Aryl-Ether-Ether-Ketone) by Plasma Ion Immersion Implantation and Deposition
M. Xu, Z. Wei, S.H. Pu, P.K. Chu (City University of Hong Kong)
Poly aryl-ether-ether-ketone (PEEK) is a high temperature and radiation resistant thermoplastic material with many potential applications in the aerospace industry, automotive industry, electronics and medical devices. However, the use of PEEK is limited because of its low hardness, poor scratch resistance, and high susceptibility to gases and chemicals. Amorphous carbon (a-C) films are known for their excellent properties including high hardness, low friction coefficient, high chemical inertness, and good corrosion resistance. Hence, a system combining PEEK and a-C is promising but the large difference in their mechanical properties makes it difficult to produce a-C films on PEEK. In this work, plasma immersion ion implantation and deposition (PIII&D) is used for the first time to prepare an amorphous carbon film on PEEK substrate. We focus on the effects of the negative bias voltage and the ratio of the acetylene to argon flow rates (FC2H2/FAr) to determine the optimal conditions under which a-C:H films up to 1 µm thick can be fabricated. The energy transfer from the incident ions induces irreversible changes in the macromolecular structure of the PEEK matrix resulting in altered properties. The film structure is evaluated by X-ray photoelectron spectroscopy and Raman spectroscopy. SEM is employed to investigate the surface morphology and cross-sections of the film. The wetting behavior is assessed using distilled water and NaCl as the media. Our results indicate that the wettability of PEEK can be improved by an amorphous carbon film and the preparation parameters affect the properties of the films significantly.
DP-12 Instability of a Droplet Between Nano-scale Dual Rough Surfaces Coated With Hydrophobic DLC Films
T.-G. Cha (Seoul National University, Korea); J.W. Yi (Korea Institute of Science and Technology, Republic of Korea); M.W. Moon (Korea Institute of Science and Technology, Korea); H.-Y. Kim (Seoul National University, Korea); K.-R. Lee (Korea Institute of Science and Technology, Korea)

Solid surface wettability could be controlled by a chemical treatment of the material surface or modification of the surface topology. The super-hydrophobic surface, having the water contact angle of over 150 ~170 degree, has drawn much attention owing to its potential applications such as a water repellent self cleaning surface, surface energy induced drop motion or flow channel of low resistance for microfluidic devices. In the previous work, by combining the nanoscale double-rough surface with a hydrophobic DLC coating, we have shown the superhydrophobic wetting behaviour of a water droplet on various surface structures on DLC coated dual rough surface[1]. Compared to single roughness surfaces with a wetting angle ~120 degree and with high wetting angle hysteresis (difference between forwarding and receding angle) ranging from 40 to 60 degrees, the dual roughness surface were achieved of 160 degree in wetting angle and less than 5 degree in hysteresis. Here we have further examined the superhydrophobic behavior on dual rough surfaces as improved the hydrophobic nature of dual surfaces by varying the deposition condition of DLC coating. Especially we have performed the systematic experiment that a water droplet, placed between the dual rough surfaces, was gradually pressed and we have monitored the variation in contact angle of the droplet from the hydrophobic to hydrophilic state with respect to hydrophobicity of dual rough surfaces.

[1]T. –Y. Kim, B. Ingmar, K. Bewilogua, K. H. Oh, K.-R. Lee , Chem. Phys. Lett. 436 (2007) 199.

DP-13 Effects of Energy Dispersion on the Atomic Structure of ta-C Films: Molecular Dynamics Study
K.S Kim (Korea Institute of Science and Technology / Kookmin University, Korea); S.C. Lee, K.-R. Lee (Korea Institute of Science and Technology, Korea); P.R Cha (School of Advanced Materials Engineering, Kookmin University)
Molecular Dynamics Study is a technique where the time evolution of a set of interacting atoms is based on empirical or semi-empirical potential. MD simulations can be used to analyze mechanical properties of material and observe the atomic structure of the system didn’t easily analyzed experimentally. MD simulation has been widely used to analyze tetrahedral amorphous carbon (ta-C) film among amorphous structure. For example to know of the mechanism which ta-C film have high residual stress is possible. But, Incident carbon energy is monochromatic when ta-C film is produced. The thing is usually known and used. The behavior of residual stress of ta-C film with incident energy correspond with an experiment results, qualitatively. But quantitatively, the difference in stress which is about 200% larger than experimental data. This study is focused on the roll of standard deviation on residual stress of ta-C film with incident energy. We presume that the incident energies of carbon atoms follow Gaussian distribution. When standard deviation of incident energy =1, residual stress of simulation is in accord with experiment data, quantitatively. As the condition experiment, the energy dispersion of incident carbon has standard deviation. This fact considered, MD simulation results are satisfied with experiment results.
DP-14 The Tribological Behaviour of Artificial Joint Coated With Diamond-Like Carbon Films Deposited by Plasma Immersion Ion Implantation
W.F. Tsai (Institute of Nuclear Energy Research, Taiwan); S.L. Tu (National Yang Ming University, Taiwan); C.F. Ali (Institute of Nuclear Energy Research, Taiwan); R. Tsay (Nation Yang Ming University, Taiwan)
Wear debris arising from the counter-friction of UHMWPE element against metal is one of the major causes for the failure of joint arthroplasty. Previous studies reported that the hardness and wear problem could be improved by coating a diamond-like carbon film on the metal surfaces. The present study investigates the effects of film deposition time, bias voltage and composition of intermediate layer on the properties of the coated DLC film deposited by the plasma immersion ion implantation technique. The results show that the film deposition rate decreases with the increase of bias voltage, which might be due to the high energy of the ion carried. Raman spectra analysis indicated that by increasing the bias voltages from 0.5 to 2 kV, the deposited film tends to form more graphite-like structure. The surface hardness is increased by the coated DLC film while the elastic modulus decreases. By increasing the bias voltages from 0.5 to 2 kV, both of the hardness and elastic modulus are increased. Frictional tests show that surface coating of a DLC film will result in the decrease of dry friction coefficient and the increase of wet friction coefficient. By increasing deposition time, the endurance time against wear of the coated film will be increased.
DP-15 The Mechanical Stability of a Diamond-Like Carbon Coated Nitinol Vascular Stent Under Cyclic Loading
H.-J. Kim (Seoul National University, Korea); M.W. Moon, K.-R. Lee (Korea Institute of Science and Technology, Korea); K.-H. Oh (Seoul National University)
It has been known that a vascular stent helps hold an artery opened by its circumferential expansion to a large diameter so that blood could flow through it. The ideal stent requires not only mechanical properties of sufficient radial strength and low recoil but also a good biocompatibility for lowering the thrombogenicity and restenosis. In order to increase both mechanical properties and biocompatibility, a metallic stent would be coated with biocompatible materials like carbon and titanium nitride. However, a film coated metallic stent in service may locally undergo a large tensile or compressive deformation, causing critical failures in the coating layers, such as film cracking and interface delamination due to a misfit strain between a film and a metallic substrate. In the work, we investigated a failure behavior of Diamond-Like Carbon (DLC) coated on a metallic vascular stent under cyclic loading of compression and tension. Using PACVD equipped with a rotation stage, a entire surface of a self-expandable vascular stent, made of a nitinol, were coated with DLC film, known for a protective coating due to its good biocompatibility and excellent mechanical performance of high wear resistance and hardness. Cyclic loading of compression and tension was applied on a V-shaped unit cell of the DLC coated stent using a screw-driven tensile tester. It was observed that channel cracking and delamination of DLC film occurred intensively in the regions subject to the tensile strain. We investigated the effects of plasma cleaning and DLC film thickness on an interfacial delamination behavior by the cross-sectional analysis of the fractured region using a FIB/SEM system.
DP-17 Mechanical Properties Evaluation of Titanium-Containing Diamond-Like Carbon Films Deposited by Cathodic Arc Plasma
P.-C. Tsai (National Formosa University, Taiwan); J.-Y. Chiang (AU Optronics Corporation, Taiwan); Y.-F. Hwang (Chienkuo Technology University, Taiwan); J.C. Huang, J.-W. Lee (Tung Nan University, Taiwan)
Diamond-like carbon (DLC) films and titanium-containing diamond-like carbon (Ti-DLC)films were deposited by cathodic arc plasma evaporation. Film characteristics were investigated using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Microstructures of the films were evaluated using an atomic force microscope (AFM), field emission scanning electron microscopy (FEGSEM, high-resolution transmission electron microscopy (HRTEM) and glancing angle X-ray diffractometry (GAXRD). Mechanical properties were investigated by using a nano-indentation tester, scratch test and ball on disc wear test. The results demonstrated that a carbide-containing DLC films were obtained by co-deposition method. Mechanical property measurements showed that the plasticity, adhesion strength of the titanium-containing DLC films were much higher than that of Ti-free DLC, while the hardness of the DLC films decreased. Wear tests indicated that the friction coefficient and the wear rate of Ti-DLC were lower than that of Ti-free DLC. The morphology of the mechanical tested samples was analyzed to evaluate the mechanical performance. Results of Raman spectra, XPS spectra and microstructure analysis will also be discussed in this study.
DP-18 Effect of Coupling Agent and TiO2 on Surface Composition and Characteristics of Polyimide/TiO2 Hybrid Films
M.-H. Tsai, S.-J. Liu (National Chin-Yi University of Technology, Taiwan); P.-C. Chiang, C.-H. Chao (Mingdao University, Taiwan); P.-J. Chen (National Chin-Yi University of Technology, Taiwan)
Composites, which are formed from two or more distinct materials, have desirable combinations of properties that are not found in the individual components. In this study, a series of PI/TiO2 hybrid film has been successfully fabricated through the sol-gel process. The 4,4'-(4,4'-Isopropylidenediphenoxy) bis (phthalic anhydride)] (IDPA), 4,4'-diaminodiphenyl ether (ODA) and 3-aminopropyltrimethoxysilane (APrTMOS) are mixed entirely to form the APrTMOS-polyamic acid (APrTMOS-PAA) solution. Tetraethyl orthotitanate (Ti(OEt)4) and actylacetone (ACAC), the latter one is used as chelating agent, are then added to the APrTMOS-PAA solution. Through the sol-gel process and thermal imidization, the cross-linked structure of PI/TiO2 hybrid film is formed. The more APrTMOS is added, the higher transparency of the PI/TiO2 hybrid film can be obtained. The glass transition temperature (Tg) and thermal stability of the hybrid films are increased by introducing the APrTMOS. Meanwhile, the surface energy of the hybrid film is decreased with APrTMOS content. On the other hand, the more TiO2 is added, the higher glass transition temperature and surface energy are observed. However, the transparency and thermal stability of the hybrid film are decreased with TiO2 content. According to the results of x-ray photoelectron spectroscopic (XPS) analysis, the hybrid film incorporated with APrTMOS shows higher content of Ti component on the top of hybrid film surface as compared with the one without APrTMOS added. This result implied that the addition of APrTMOS could facilitate the migration of Ti component toward the surface of hybrid film.
DP-21 Synthesis of Ti2AlN Thin Films by Plasma Nitridation of Titanium Aluminides
T. Cabioch, F. Pailloux, M. Jaouen (University of Poitiers, France)

To better understand the formation of Ti2AlN when titanium aluminides are used as templates, we studied by X-Ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and Glow Discharge Optical Spectroscopy (GDOS) the first stages of the nitride formation when plasma nitridations of bulk TiAl and Ti3Al samples, but also of TixAl1-x thin films (0,47 ≤x ≤0,66) deposited onto Si(100) substrates or bulk TiAl, were achieved between 600°C and 900°C.

XRD and cross-sectional TEM observations clearly indicate that this nitridation process first leads in almost all cases to the growth of a Ti2AlN thin layer instead of TiN, this result being attributed to the very low solubility of nitrogen into TiAl but also to the relationships between the structures. Furthermore, in the case of TixAl1-x thin films deposited onto bulk TiAl or silicon substrates, strongly textured (0002) Ti2AlN thin films were obtained. On the contrary no nitride formation was achieved when Ti3Al was used as a template, a result that explains why a complete transformation of Ti2Al thin films into Ti2AlN is not achieved after the nitridation treatment. Our results strongly suggest that a rapid formation of Ti2AlN is obtained when very fine grains of TiAl are submitted to the nitrogen plasma. This was confirmed by HRTEM cross-sectional observations of nitrided TiAl thin films or by GDOS characterizations that clearly indicate the low diffusion of nitrogen into large TiAl grains.

DP-23 Influence of Substrate Bias on the Morphology and Field Emission Properties of AlN Thin Films Grown at Low Temperatures
R.S. Pessoa, H. Toku, M.A. Fraga, H.S. Maciel, M. Massi, A.S. da Silva Sobrinho (Technological Institute of Aeronautics, Brazil); L.V. Santos (INPE/MCT-Instituto Nacional de Pesquisas Espaciais, Brazil)

Recently, field emission (FE) properties of AlN thin films have called attention because the similar properties to diamond. Moreover, their high mechanical strength and excellent chemical stability are favourable for construction of long lifetime FE-based devices.

In this work, low temperature (less that 75°C) AlN thin films were deposited on Si(100) substrates by DC sputtering technique under various applied negative bias voltage ranging from 0 to -200V. The influence of negative substrate bias on the surface morphology and FE properties of as-deposited films has been studied and correlated. For this, AFM measurements were realized for analysis of surface morphology. The FE properties were investigated by measurements of FE characteristics curves and Fowler-Nordheim plots of the films. The measurements showed that low values of turn-on field (approx. 0.4 V/µm) can be obtained. From these results, we have observed that the negative dc bias voltage improves the crystallinity level and orientation for AlN films grown under low substrate temperature. Furthermore, we observed that this technique allows us to control the RMS roughness and the peaks density on the film surface, giving rise the possibility of growing AlN films with high emission current densities.

DP-24 Electron-Emission Properties of Titanium Carbide-Coated Carbon Nanotubes Grown on a Nano-Sized Tungsten Tip
Y.K. Kim, J.P. Kim, C.K. Park, S.J. Yun, W. Kim, J.S. Park (Hanyang University, Korea)
Recently, the x-ray tube using a carbon nanotubes (CNTs)-based cold cathode has been reported to yield better resolved x-ray images than that using the conventional thermionic emitters. To realize a micro-focused x-ray tube using a CNTs-based cold cathode, the emittance of electron beam should be decreased as small as possible, but this manner brings about reduction of emission current level. Furthermore, when the CNTs grown on a micro-tip shaped substrate are used as emitter, the degradation of CNTs at the emitter-summit due to prolonged emission of electrons is a crucial problem to be overcome. Titanium carbide (TiC) is known to have good electrical and thermal conductivities, high melting point and hardness, and a low work function (~ 3eV). This work aims to enhance the electron-emission properties and the stability of field emitters based on CNTs by coating the thin TiC layer. The CNTs are directly grown on a nano-sized (< 500nm) W-tip with Ni catalyst and Al/Ni/TiN buffer by using an inductively coupled plasma-chemical vapor deposition system. Prior to TiC-coating, CNTs are annealed at 700°C in He atmosphere and Ti films are deposited on CNTs by RF magnetron sputtering. The synthesis of TiC is performed at 700°C by introducing the C2H2 gas. Morphologies and microstructures of TiC-coated CNTs are monitored by SEM and TEM. Raman spectroscopy is also used to analyze the carbon structure and the crystal quality of CNTs. Effects of TiC-coating on electron-emission properties of the CNTs-based field emitters are examined by characterizing the threshold voltage for electron-mission, the maximum emission current, and the long-term stability.
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