Papers

ICMCTF2002 Session DP-1: Symposium D Poster Session

Monday, April 22, 2002 5:00 PM in Room Town & Country

Monday Afternoon

Time Period MoP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2002 Schedule

DP-1-1 The Effect of Bias Control on the Synthesis of a-C:N Nanotubes and Nanofibers by ECR-plasma X. W. Liu, J.H. Lin, W.J. Hsieh, H.C. Shih (National Tsing Hua University, Taiwan, ROC) Amorphous carbon (a-C:N) nanotubes and nanofibers on a porous alumina template were synthesized by an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system in which a various negative dc bias was applied to the substrate holder of graphite to promote the flow of ionic fluxes through the nano-channels of the alumina template in microwave excited plasma of Csnb 2Hsnb 2, Nsnb 2 as precursors. The aligned structure of a-C:N nanotubes and nanofibers were verified by field emission scanning electron microscopy (FE-SEM). Transmission electron microscopy (TEM) micrographs of a-C:N nano-rods showed that the nano-rods with a diameter of about 100-250 nm and a length of about 50-80 mm are well-aligned. The amorphous nature of the nano-rod was confirmed by the absence of crystalline phases arising from selected area diffraction (SAD) patterns. X-ray photoelectron spectroscopy (XPS) spectra indicated that these nanotubes and nanofibers was composed of nitrogen and carbon, and the N/C ratios could reach as high as 72 and 56 %. The absorption bands between 1250 and 1750 cm-1 in Fourier transform infrared (FTIR) spectroscopy provided a direct evidence for the nitrogen atoms that have effectively incorporated into the amorphous carbon network. Raman spectra showed the same feature of possessing a G-band at ~1580 cm^-1 and a D-band at ~1370 cm^-1 with the amorphous carbon film. The well-aligned a-C:N nanotubes and nanofibers can be predicted and expected to have potential applications in optic, electronic and optoelectronic devices.
DP-1-2 Carbon Nanotube Growth with the Aid of Cobalt Silicide Catalysts H.L. Chang, C. T. Kuo (National Chiao Tung University, Taiwan, ROC) Carbon nanotubes have been successfully synthesized by microwave plasma chemical vapor deposition method using cobalt silicide catalysts. Controllable shape morphologies were achieved by adjusting the synthesis process. Quasi-aligned nanotubes with bamboo-like structure were grown by CH₄and N₂ gaseous sources. Interesting, the cone shape nanotubes were grown by CH₄ and H₂ gaseous sources and TEM image indicates that this cone shape nanotubes were filled in metal inside the tube channel and on the top is a metal droplet. TEM, SEM, Raman, Auger and field emission characteristics characterized film microstructure, morphologies, band structure, composition, field emission property, respectively. Selective growth of carbon nanotubes were produced on wafer patterned with arrays of 1.8 µm diameter holes, where a thin cobalt silicide film was formed previously on the bottom of holes. This is a novel method compatible with semiconductor manufacturing and also provides a way for selective growth of carbon nanotubes.
DP-1-3 Well-aligned Carbon Nanotube Parallel to Substrate C.M. Hsu, H.L. Chang, C.H. Lin, C. T. Kuo (National Chiao Tung University, Taiwan, ROC) Low temperature growth of carbon nanotubes has been successfully synthesized on indium-tin-oxide (ITO) glass and Si substrate by microwave plasma chemical vapor deposition (MPCVD) method, using electroplated Co as catalysts material. We developed a technique that enables controlled synthesis of nanotube direction by adding additional capping layer on the substrate with a gap of several microm. And direction of nanotubes is controllable by adjusting the gap distance between capping layer and substrate, where for no capping layer the nanotube is growth perpendicular to the substrate. The preliminary results indicate that well-aligned carbon nanotube parallel to substrate shows significant emission current. Field emission property of different orientated carbon nanotubes will be compared. TEM, SEM, I-V measurement and Auger will characterize the film microstructure, morphology, field emission property and composition. The growth mechanism of nanotubes under the gap will be discussed.
DP-1-4 Ordered Carbon Structures Deposited By Hot-Filament CVD Using High Helium Concentrations V. Baranauskas (University of Oxford, United Kingdom); H.J. Ceragioli, A.C. Peterlevitz, S.F. Durrant (Universidade Estadual de Campinas, Brazil) Growth of carbon structures in the form of wires and nanotubes has been accomplished by the use of helium at very high concentrations (99.5 % vol.) in the feed mixture of a hot-filament CVD reactor. Ethanol vapor (0.5 % vol.) was used as the carbon precursor. Scanning electron (SEM) and transmission electron (TEM) microscopy analysis of the deposited material revealed that the use of helium as a diluent in the vapor phase favors the growth of spongy-like structures, ranging from micro-wires to nanotubes. Different structures are observed at different deposition temperatures. Raman spectroscopy, up to the fourth order scattering, was used to identify the chemical bonds and their structural resonances in the deposited material.
DP-1-5 Bias Effect on the Growth of Carbon Nano-tips Using Microwave Plasma Chemical Vapor Deposition C.-L. Tsai, C.-F. Chen (National Chiao-Tung University, Taiwan, ROC) The vertically aligned carbon nano-tips with high aspect ratio have been directly grown using microwave plasma-enhanced chemical vapor deposition (MPECVD) under bias effect. Due to the nano-tips grown in a high carbon concentration of the methane-carbon dioxide gas mixtures, the growth rate is better than conventional mixtures by using hydrocarbons diluted in hydrogen. In this study, the methane-carbon dioxide gas system is used. Under bias effect, the selective area deposition of well-aligned and sharp nano-tips was successfully achieved on patterned metal films. By the means of scanning electron microscopy (SEM), the growth rate and the morphology are significantly influenced by the bias. In addition, the size and uniformity of metal film also affect the growth of carbon nano-tips. Carbon nano-tips also have good performance on the application of field emission. The further information will be presented at conference.
DP-1-6 Synthesis of Pd Filling Multi-walled Carbon Nanotubes and Pd Nanowires by Microwave Plasma Chemical Vapor Deposition L. H. Chan, K. H. Hong, S. H. Lai, X. W. Liu, H.C. Shih (National Tsing Hua University, Taiwan, ROC) Multi-walled carbon nanotubes were synthesized on electroplated Pd films, using a microwave plasma enhanced chemical vapor deposition system with a mixture of methane and hydrogen. During the synthesis process, the molten Pd was able to fill through the central hollow area of multi-walled carbon nanotubes, and the morphologies were observed by transmission electron microscopy. A growth mechanism was proposed to describe Pd filling phenomena. In addition, samples were followed by oxygen plasma etching process to burn out the multi-wall carbon nanotubes and the Pd nanowires were revealed. Scanning electron microscopy was used to examine surface morphologies of electroplated Pd films, and transmission electron microscopy was applied to investigate the nanostructures of multi-walled carbon nanotubes and Pd nanowires. Raman spectra were assisted to study the first-order and second-order signals of multi-walled carbon nanotubes. Otherwise, it was found that bamboo shape carbon nanotubes were synthesized under methane atmosphere without hydrogen.
DP-1-7 Growth of Carbon Nanotubes by Microwave Plasma Chemical Vapor Depsotion using CH₄ and CO₂ Gas Mixture M. Chen, C.-M. Chen (National Chaio-Tung University, Taiwan, ROC); C.-F. Chen (National Chiao-Tung University, Taiwan, ROC) Carbon nanotubes were grown vertically and aligned on Fe catalytic nanoparticles which were deposited on a Si substrate at low temperature using CH4 and CO2 gas mixtures. A dynamic form of optical emission spectroscopy was used to detect the species in the plasma. These data show the dominant species in gas phase reaction. After deposition, the morphology and the quality of carbon nanotubes was determined using scanning electron microscope, high-resolution transmission electron microscope and laser Raman spectroscope. The results showed that as microwave power was set at 300W and the pressure range 10~15 torr, the ratio of CH4/CO2 flow rate was changed from the range of 100% to 70%, and the negative DC bias voltage was adjusted from â€“150V to -200V. However, the higher quality vertically aligned multi-wall carbon nanotubes were obtained.(detail data will show in conference).
DP-1-8 Fabrication of Carbon Cones and Nanowires by Ion sputtered Graphite N.G. Shang, X.M. Meng, W.K. Wong, F.Y. Meng, Y. Lifshitz, C.S. Lee, I. Bello, S.T. Lee (City University of Hong Kong, P. R. China) Since Iijima found carbon nanotube in 1991, it has received much attention due to its excellent mechanic and electronic properties. In addition to the traditional methods of arc discharge and chemical vapor deposition, ion beam (sputtering) deposition has been used to fabricate carbon nanotubes. In the present work, Ar ion sputtering of graphite plates surrounded with metal sheets induced the formation of carbon cones and nanowires over a large area on the graphite plates. Scanning electron microscopy shows aligned carbon cones with some tips shrunk into carbon nanowires of 40 to 350 nm in diameter and 500 nm to 25 µm in length. Transmission electron microscopy studies reveal that there are also carbon nanowires of several nanometers in diameter with a preferential orientation quite different from the graphite plate on which the nanowires were grown. The formation mechanism of carbon cones and nanowires may be attributed to a combined effect of the preferential sputtering, stress in the growing film and crystal growth.
DP-1-10 Characterization of Structures, Compositions and Field Emission Properties of Carbon Nitride Nanotubes by Microwave Plasma Chemical Vapor Deposition L. H. Chan, K. H. Hong, S. H. Lai, X. W. Liu, H.C. Shih (National Tsing Hua University, Taiwan, ROC) Carbon nitride nanotubes were synthesized on electroplated Pd films, using a microwave plasma enhanced chemical vapor deposition system with a mixture of methane, hydrogen and nitrogen. The nanostructures were investigated by high resolution image and SAD (Selected Area Diffraction) pattern of transmission electron microscopy. EELS (Electron Energy Loss Spectroscopy) and XPS (X-ray photoelectron spectroscopy) were assisted to study how nanostructures varied with increasing content of nitrogen. In our field emission test, carbon nitride nanotubes has properties superior to those of carbon nanotubes, such as smaller turn-on voltage and larger current density. Field emission properties of carbon nitride nanotubes with different nitrogen content were also compared and discussed on Fowler-Nordheim coordinates.
DP-1-11 Field Emission Properties of Aligned Carbon Nanotubes Growing on Bias-enhanced Plasma Pretreated Cr Film C.-F. Chen, C-L. Lin, C.-M. Wang (National Chiao-Tung University, Taiwan, ROC) In this report, the aligned carbon nanotubes have been grown on Cr film by bias-enhanced microwave plasma chemical vapor deposition using CH₄/H₂ and CH₄/CO₂ two systems source gases. Cr film on silicon wafer is at a constant thickness of 1000, and bias-enhanced plasma pretreatment was performed in various periods for modifying surface condition of Cr film. H₂ and CH₄/CO₂ plasma pretreatment were selected for CH4/H2 and CH4/CO2 deposition, respectively. In our preliminary results, we found that pretreatment period and source gases were major parameters in affecting the surface conditions of Cr film, and then the resulted nanotubes and their properties. The surface roughness, grain size and particle size of pretreated Cr film were analyzed by AFM, and compositions were examined by x-ray diffraction. The morphology and distribution of nanotubes were observed by SEM, the quality was analyzed by Raman spectroscopy, and the structure was characterized by HRTEM images. Finally, we used I-V measuring system to obtain the field emission characterization. A light emission device was fabricated using carbon nanotubes as a cathode, and the ITO glass with a printed ZnO:Mn blue phosphor as an anode plate. This device involving gap structure between the cathode and the anode. Effects of pretreatment condition on the resulted nanotubes structures and properties have been studied and the results will be presented at conference.
DP-1-13 The Effect of Graphitization by Argon on the Electron Field Emission Properties of the a-C:N Thin Films X. W. Liu, J.H. Lin, W.J. Hsie, H.C. Shih (National Tsing Hua University, Taiwan, ROC) Amorphous carbon nitride thin films were synthesized on silicon as electron emitters by the electron cyclotron resonance chemical vapor deposition (ECR-CVD) system in which a negative dc bias was applied to the substrate holder of graphite and a mixture of Csnb 2Hsnb 2, Nsnb 2 used as precursors. The addition of Ar combined with the application of a negative dc bias can eliminate the dangling bonds in the film determined by Fourier transform infrared (FTIR) spectroscopy, decrease the film thickness measured by field emission scanning electron microscope (FE-SEM), increase the film roughness measured by atomic force microscope (AFM) and raise the graphitic content examined by Raman spectroscopy. An onset emission field of amorphous carbon nitride (a-C:N) with Ar as an extra addition to the precursors can be as low as 6.5 Vµm^-1 compared with 9.5 Vµm^-1 of the film without the addition of Ar.
DP-1-14 ECR-CVD Deposition of Thermally Stable Amorphous Carbon Nitride Thin Films with Low Dielectric Constants X. W. Liu, J.H. Lin, W.J. Hsieh, H.C. Shih (National Tsing Hua University, Taiwan, ROC) Amorphous carbon nitride (a-C:N) and fluorinated amorphous nitride carbon (a-C:N:F) films were synthesized on silicon as new low-dielectric-constant materials by using an electron cyclotron resonance / chemical-vapor deposition (ECR-CVD) system with an application of negative rf bias to the silicon substrate in a mixture of Csnb 2Hsnb 2, Nsnb 2, and CFsnb 4 as precursors. The dielectric constants (k) of a-C:N and a-C:N:F thin films were found to be as low as 1.4 and 1.2, at 1 MHz, respectively. The thermal stability of the films has been improved by the incorporation of nitrogen atoms into the amorphous carbon network. The dielectric constants of a-C:N:F thin films could be lowered due to the addition of fluorine atoms. The basic structure, composition, and electronic properties of these films were analyzed by Fourier transformation infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), field-emission scanning electron microscopy (FE-SEM), and dielectric-constant measurements. The dielectric constants of a-C:N thin films can be significantly lowered by the formation of the cross-linked structure and hard C-N bonds in the films due to increasing the N/C ratios, and sp³-bonded carbon contents in the a-C:N films with the decreasing of substrate negative rf bias.
DP-1-15 Thermal Diffusion of Aluminum on Near Stoichiometric a-SiC:H Films A.R. Oliveira, M.N.P. Carreño (Universidade de São Paulo, Brazil); I. Pereyra (Escola Politécnica da USP, Brazil) During the last few years silicon carbide has attracted considerable interest due to its advantages over silicon for high temperature, high power and high frequency applications, motivating research on the material production and characterization. In this way we have demonstrated the possibility of obtaining at low temperatures (320°C) and by plasma enhanced chemical vapor deposition (PECVD) an amorphous counterpart of crystalline SiC which preserves some of the notorious properties of this material (a-Si_0,5C_0,5:H). On the other hand, in order to driven the development of SiC based electronics devices, selective area doping technology is essential. Aluminum is as excellent acceptor impurity for SiC but,differently than for silicon, Al thermal diffusion is not an effective doping technique for this material, since the diffusion coefficient of Al in SiC is very small and the effective diffusion occurs only at very high temperatures (greater that 1800°C). On the other hand, previous results have show that Al diffusion in our amorphous SiC is very much efficient than in crystalline SiC and in this work, with the aim of investigating the P-type doping by this technique, we develop a series of thermal diffusion experiments. Therefore, we study different diffusion times and temperatures and correlate them with the electrical properties of the a-Si_0,5C_0,5:H films. Preliminary results indicate an effective doping effect, suggesting that this technique can be a real option for doping this type of SiC films.
DP-1-17 Thin Film Structural Stabilization using Low Energy Ion Beam Assisted Deposition W. otano, V. Pantojas, N. Vazquez (University of Puerto Rico at Cayey) Boron nitride is a model system to study thin film nucleation and growth. Energetic bombardment during film growth, e.g., a high flux of particles with energies over 50 eV, has been one of the process parameters necessary to stabilize the boron nitride cubic structure (cBN) instead of the stable hexagonal phase. Using ion beam assisted deposition (IBAD), several authors have been able to correlate this energetic bombardment with P/a, the total momentum imparted to the growing film per arriving boron atom. Kaufman sources used in these previous IBAD studies provide a moderate amount of ion current with energies in the 200-500 eV range. Plasma glow discharge methods have been used at lower energies but accurate measurements of the bombarding ion fluxes and energies are difficult. In this research project an End-Hall ion source has been incorporated to the IBAD system to study the cBN thin film nucleation at bombarding ion energies in the 50-120 eV range. This source is able to increase the ion current by a factor of 2 as compared to the traditional Kaufman sources. Because P/a is proportional to the product of the bombarding ion flux and the square root of the bombarding ion energy, an increase of two in the flux allows decreasing the ion energy by a factor of four. Bombarding the growing film with ions of 100 eV produces the same energetic bombardment as a Kaufman source with ion energies of 400 eV. The formation of boron nitride thin films using this system, and the implications for the nucleation process of the cubic phase, will be presented.
DP-1-18 Mechanical Properties of Amorphous Boron Carbon Nitride Films Produced by Dual Gun Sputtering S.C. Chien, S. Chattopadhyay, L.C. Chen, S.T. Lin (National Taiwan University, Taiwan); K.H. Chen (Institute of Atomic and Molecular Sciences, Taiwan) Boron carbon nitride (BCN) enjoys the proximity, in terms of the micro-hardness values, to that of diamond and hence an important material for industrial applications. Problems faced by diamond in high temperature cutting applications involving ferrous alloys and the comparatively lower hardness of c-BN has put BCN in an important frame. A dual gun sputtering system was employed to grow amorphous BCN (a-BC_xN_y). Hardness and roughness of the films were studied by nanoindentation techniques and atomic force microscopy, respectively. Measurements of the hardness and elastic modulus of a-BC_xN_y films having different carbon concentrations reveal that ~25 at. % of incorporated carbon produced the best films, at a substrate temperature of 75Â°C. Increasing carbon concentrations resulted in certain soft phases that deteriorated the film properties. For a higher substrate temperature, however, more carbon could be incorporated in the amorphous matrix in the favourable coordinated phases. The chemical composition and phase identification was done collectively by X-ray Photoelectron spectroscopy, Auger Electron spectroscopy and Fourier Transform Infra red spectroscopy, to reveal the hybridisation levels of the constituent elements and to show the evolution of different phases in the a-BC_xN_y network.
DP-1-19 Micro-tribological Properties of Boron Carbide and Carbon Films T. Saitoh, S. Miyake, W. Shuichi (Nippon Institute of Technology, Japan) Micro-tribological characteristics of a diamond like carbon (DLC) and boron carbide (B-C) films and nitrogen ion implanted those films were evaluated by atomic force microscope (AFM). Adhesion and strength of film were evaluated by an oscillatory scratching test with acoustic emission (AE). Nanoindentation hardness and elastic modulus of B-C film is higher than those of DLC films. Nanoindentaton hardness and elastic modulus of both those films increased by ion implantation. Microwear of B-C film was smaller than that of DLC film, similar to nanoindentation hardness evaluated by AFM. Microwear resistance in microscratching test of DLC film was remarkably improved by N⁺-implantation. However, micro wear of B-C film decreases contrarily by N⁺-implantation in spite of its hardness increase. From the evaluation of oscillatory scratching test, a critical load of DLC film that AE counts increases rapidly and film fracture occurred, remarkably increased by N⁺-implantation. However, critical load of B-C remarkably decreases by N⁺ implantation. These results correspond to micro-wear properties in micro-scratching test. In oscillatory scratching test of DLC film, damage at low load was small and mainly consisted of plastic deformation. In this case, the waveform was continuous, wave amplitude was small, and high-frequency component was little. At higher load, brittle fracture occurred, and large amplitude and high-frequency components increased. Damage of N⁺-implanted DLC film is also small in the condition that AE occurs. Sudden type waveform increased,though amplitude is small. In oscillatory scratching test of B-C film, sudden type waveforms were observed at the beginning of AE occurrence and higher-frequency component as 400 kHz was obtained than that from DLC film. A clear brittle fracture of B-C film is speculated to cause sudden type waveform and high-frequency components more than 400 kHz.
DP-1-20 XPS and XRR Studies on Microstructures and Interfaces of DLC Films Deposited by FCVA Method C.K. Park, S.M. Chang, H.S. Uhm, S.H. Seo, J.S. Park (Hanyang University, Korea) One of the most important factors governing the film quality of diamond-like carbon (DLC) is the hybridized sp³/sp² atomic carbon ratio. Among the successful methods for the preparation of DLC films, the filtered cathodic vacuum arc (FCVA) method has been known to produce highly tetrahedral-bonded amorphous carbon films at reasonable deposition rates. In determining the sp³/sp² ratio of DLC films, several techniques have been used. The most commonly used techniques are electron energy loss spectroscopy (EELS), near edge x-ray absorption fine structure (NEXAFS), and Auger electron spectroscopy (AES). However, there are still some ambiguities related to the interpretation of the spectra obtained using EELS and NEXAFS. On the other hand, the electron beam used in AES can induce structural modifications of the DLC film during analysis. Recently, xray photoelectron spectroscopy (XPS) has been used to directly decompose the C 1s peak into sp² and sp³ peaks, and subsequently evaluate the sp³ content in DLC films. In addition, x-ray reflectivity (XRR) has also been proposed to study the film density, surface roughness, and layered structure of DLC films without destroying the samples. However, for the DLC films prepared by the FCVA method, there has been few studies on the structural analysis using these techniques. In this paper, we present the XPS and XRR results of DLC films prepared by using a compact FCVA deposition system and produce a quantitative information on the microstructures of the DLC films as well as the DLC/Si interfaces. DLC films were deposited at room temperature by varying the substrate-bias voltage ranging from 0 to -250V. The I_D/I_G intensities and G-band peak widths were monitored by the Raman spectroscopy. The sp³/sp² ratios of the deposited DLC films were evaluated from the deconvoluted data of XPS spectra of the C 1s core level. It was observed that the sp³ content in the DLC films was almost monotonically decreased with the substrate bias, which was in good agreement with the result obtained from the Raman spectra. The depth profiles of the XPS spectra from the C 1s, Si 2p, and O 1s core levels were obtained by accompanying the Ar⁺ beam etching of the sample with the XPS measurements. From the XPS depth profile the DLC film was modeled as a structure having three different layers, such as surface, bulk, and interface. Using the XRR technique has successfully produced a quantitative information on the density, roughness, and thickness of each layer in the DLC film. High-resolution transmission electron microscopy (HRTEM) studies on the DLC films will also be discussed.
DP-1-21 On Tribological Performance of Diamond-like Carbon Films Synthesized by a Hybrid Filter-Arc Evaporation Process K.W. Weng (National Chung Hsing University, Taiwan, ROC); D.-Y. Wang (Mingdao University, Taiwan, ROC) Damond-like carbon film (DLC) was synthesized successfully using a hybrid PVD process consisting of a filter arc evaporator and a Metal plasma ion implanter (MPII). Density of macroparticles was substantially reduced by a quarter torus plasma duct filter. Graphite targets were used in the cathodic arc evaporation process. Intensive electron and ion energy generated from the plasma duct facilitate the activation of carbon plasma and deposition of high quality DLC films. To enhance the film adhesion and surface properties, DLC films were co-deposited with high-energy carbon ions at 2x10¹⁷ atmos/cm² dosage. The ion energy is maintained at 45 KV. The effect of ion mixing at film interface is examined using TEM microscopy. The phase transformation and reduction of residual stress at the film surface are investigated.
DP-1-22 Catalysis Effect of Metal Doping on Wear Properties of Diamond-like Carbon Films Deposited by Cathodic Arc Evaporation Y.-Y. Chang (National Chung-Hsing University, Taiwan, ROC); D.-Y. Wang (Mingdao University, Taiwan (ROC)); W.T. Wu (National Chung-Hsing University, Taiwan, ROC) Diamond-like Carbon films (DLC) containing various metal dopings were synthesized by cathodic arc evaporation process with pulsed plasma technology. Metal plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gas (C₂H₂), and induces the formation of the hydrogenated DLC film with a mixture of sp² and sp³ carbon bonds. The composite film structure consists of a metal- doped DLC films and a graded metal nitride interlayer. To improve the adhesion and toughness, the catalysis effect of various metal contents was investigated by X-ray diffraction (XRD), Raman spectroscopy (RS), and x-ray photoemission spectrometry (XPS). Tribological performances such as friction coefficient, and wear life were evaluated by using pin-on-disk tests as well as field analysis. Results reveal the correlation between the wear properties and the metal doping. The Cr-C:H carbon film exhibits a dense microstructure and a higher sp³ bond ratio, showing great potential in wear performance. Details in DLC deposition and wear analyses will be discussed.
DP-1-23 Effects of Ti Interlayer on Nitrogenous DLC Coatings Prepared by the Filtered Cathodic Arc Technique M.-S. Leu, S.Y. Chen (Industrial Technology Research Institute, Taiwan, ROC); B.F. Chen (Materials Research Laboratories, Industrial Technology Research Institute) Properties of nitrogenous diamond-like carbon (DLC-N) films prepared by filtered cathodic arc deposition technique are reported. Emphasis is placed on the effect of the thickness of the titanium interlayer on the adhesion property, film surface roughness, film hardness and sp³/sp² bonds ratio of the nitrogenous DLC coating prepared. Significant improvement of adhesion property, as evaluated by the scratch test was observed, as the thickness of the interlayer was increased. However, the surface roughness and hardness values were deteriorated with the increasing thickness of the Ti interlayer. A maximum microhardness value of Hv=5,000 was obtained corresponding to a minimum Ti interlayer thickness. In addition, the Raman spectroscopy showed the ratio of sp3 bonds of about 72 % in the (DLC-N) coating obtained.
DP-1-24 The Effect of Substrate Bias and Nitrogen Incorporation on the Diamond-like Carbon Film Depositions by 90°-bend Magnetic Filtered Cathodic Arc Evaporation Plasma W.J. Hsieh, P.-S. Shih, J.H. Lin, H.C. Shih, X. W. Liu (National Tsing Hua University, Taiwan, ROC) The properties of nitrogen incorporated diamond-like carbon (DLC) films were deposited on silicon (111) wafers by a 90°-bend Magnetic filtered cathodic Arc Evaporation Plasma system .The structure and properties have been studied by TEM/EELS, Raman spectra, Vickers hardness, RBS, and SIMS spectra. For the DLC depositions using highly ionized energetic plasma, carbon ions with varying energies can form different types of carbon bonding in the films. The energies can be controlled by applying a variable bias to the substrate. It has been reported that the DLC films have the highest hardness with a substrate pulsed bias between ¡V100V to ¡V150V, and the maximum sp³ bonding content can be obtained at a pulsed bias of ¡V150V (duty cycle:50%) is up to 85% as measured by ESCA. The DLC films have a higher hardness when the content of sp³ bonds have a higher fraction of sp³ bonding contents. The hardness seems to be related to the Raman I(D)/I(G) ratio. It also founds that nitrogen content increases with increasing substrate bias and the deposition temperature on DLC films. However, the deposition above 400°C causes a sudden loss of sp³ bonding. The maximum incorporation of nitrogen to the DLC films was measured up to 15%(N) by SIMS as well as RBS.
DP-1-25 Influence of Ion Energy and Surface Temperature on the Constitution of Highly Tetrahedral Hydrogenated Carbon Thin Films S. Sattel, P. Pesch (TZO GmbH, Germany); K. Lang (Nuenschweiler, Germany); S. Ulrich, M. Stueber (FZK IMF1, Germany) Highly tetrahedral hydrogenated amorphous carbon thin films have been deposited by a plasma beam source (PBS). The PBS consists of a capacitive coupled, magnetically confined, high frequency (13.56 MHz), low pressure (0.02 Pa) acetylen plasma discharge. As a result from energy and mass analysis the film forming particle flux consists to a main extent (95%) of C₂H₂+ ions. The ion current density amounts to be 0.2 mA/cm². The influence of the deposition temperature TS (30°C < TS < 400°C) and of the ion energy per C-atom Eion,C (65 eV < Eion,C < 260 eV) on the film constitution (XRD, EELS) as well as on the film properties (stress, density) has been investigated systematically. A new model is proposed to describe quantitatively the film densification by direct subsurface ion implantation and the film relaxation processes, induced by both, ion bombardment and substrate temperature.
DP-1-26 Influence of the Chromium Content on the Mechanical Properties and Microstructure of Chromium-Containing Diamond-Like Carbon Coatings A. Lee (National Sun Yat-sen University, Taiwan); H. Huang (Chinese Military Academy, Taiwan, ROC); D. Gan (National Sun Yat-sen University, Taiwan, ROC); Y. Yang, T. Cho (Metal Industries R & D Center, Taiwan, ROC) Cr-containing diamond-like carbon coatings (Cr-DLC) with gradient interlayers were studied to elucidate the effects of Cr content on the mechanical properties and microstructure of the deposited coatings. The coatings were deposited with a closed field unbalanced magnetron sputtering (CFUBMS) system. Mechanical properties of the coatings were evaluated with micro-indenter, scratch tester, ball-on-disk tribo-tester and ball crater. Microstructures of the films were characterized by SEM, TEM, and Raman spectroscopy. Experimental results show that an increases in Cr content from 5 at.% to 30 at.% for the Cr-DLC coatings deposited at substrate bias of -40V results in the increase of the hardness, Young's modulus, adhesion and friction coefficient. TEM analysis revealed layered structure of about 35 nm period and fine CrC crystallites of 5~10 nanometer in size on the top layer of the Cr-DLC coatings.
DP-1-27 Structural and Electrical Properties of Co-sputtered Fluorinated Amorphous Carbon (a-C:F_x) Film H-S. Jung (Yonsei University, Korea); H-H. Park (Yonsei Univeristy, Korea) This work presents the results of deposition and characterization of fluorinated amorphous carbon (a-C:F_x) by co-sputtering of polytetrafluoroethylene (PTFE) and graphite targets. The process-structure-property relationship was investigated in detail to assess the potentiality of a-C:F_x film for electrical application. Structural properties of these films are controlled by processing conditions such as sputtering power and deposition temperature. From this process, F/C ratio for these films is in range of 45-65 %, and films contain no hydrogen. The bonding configurations have been identified from X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FT-IR) spectroscopy and Raman spectroscopy. The C-F bonding configurations exist in the film as C-C/H, C-CF_x, C-F₁, C-F₂, and C-F₃. F/C ratio and the fraction of C-F₂ and C-F₃ have a proportional relationship. Concerning with the thermal stability of this film, film stress and shrinkage were evaluated at various temperatures after anneal up to 500°C.
DP-1-28 Structural and Mechanical Properties of Fluorinated a-C:Si:H Films E.C. Rangel, P.A.F. Silva (UNESP, Brazil); N.C. Da Cruz (UNESP/FEG, Brazil); R Landers (UNICAMP, Brazil); S.F. Durrant (Universidade Estadual de Campinas, Brazil) Complex amorphous hydrogenated carbon films also containing silicon and fluorine were produced from hexamethyldisilane - carbon tetra-fluoride - argon mixtures by ion implantation by plasma immersion. Films were produced at different proportions of CF₄ in the chamber feed, RF. Argon was used as a plasmogenic gas, its flow rate being controlled such that the total feed flow rate was constant. Chemical structure and composition of the films were examined as a function of RF by infrared reflectance-absorbance and x-ray photo-electron spectroscopies. The dependencies of the Young’s modulus and hardness of the films on RF were determined using nanoindentation. Surface energy and contact angles were also determined. Critical discussion of the observed dependencies of the mechanical properties on RF is presented.
DP-1-29 Amorphous Carbon Layer Deposition on Plastic Film by PSII S. Watanabe, M. Shinohara, H. Kodama (Hiroshima Institute of Technology, Japan); T. Tanaka (Hiroshima Iinstitute of Technology, Japan); T. Takagi (Hiroshima Institute of Technology, Japan); M. Yoshida (Mitsubishi Heavy Industries Ltd, Japan) Plasma source ion implantation (PSII) was successfully used to form a thin amorphous carbon layer on the surface of polyethylene terepthalate (PET) film, applying high negative voltage pulses (~10 ms pulse width, 300-900 pps, -10 kV) to the sample immersed in C₂H₂ gas with and without Ar. This pulsed voltage condition was found to generate the plasma by itself covering the substrate and the PET film to form the carbon thin layer. The oxygen barrier characteristics of the PET were improved remarkably by the formation of the thin amorphous carbon layer. Based on laser Raman, x-ray photoelectron and Fourier-transform infrared spectroscopy spectra and scanning electron microscopy observations, the thin amorphous carbon layer was found to consist primarily of graphite crystal with the characteristic of diamond-like carbon. And the ratio of sp² (graphite) to sp³ (diamond) was found to vary according to the gas pressure of C₂H₂ and adding Ar to C₂H₂.
DP-1-30 Investigation of the Alignment Phenomena Using the Diamond Like Carbon Thin Films for Liquid Crystal Alignment Materials S.J. Rho, D.K. Lee, H.-K. Baik, J.Y. Hwang, Y.N. Jo, D.S. Seo (Yonsei University, Korea) We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of diamond like carbon (DLC) thin films. The DLC thin films were fabricated by remote plasma enhanced chemical vapor deposition (RPECVD) method using the C₂H₂ and He gases. The deposited DLC thin films were irradiated by argon ion beam using the Kaufman type ion gun at 200eV. A good LC alignment by ion beam irradiation and the pretilt angles were efficiently changed by the variations of the deposition conditions and ion beam irradiation conditions. A good LC alignment was observed at the annealing temperature of 200 °C, and the alignment defect of the NLC was observed above annealing temperature of 220 °C.
DP-1-31 Mechanical Properties of Nitrogenated Plasma Polymers N.C. Da Cruz (UNESP/FEG, Brazil); P.A.F. Silva, E.C. Rangel (UNESP, Brazil); R Landers (UNICAMP, Brazil); S.F. Durrant (Universidade Estadual de Campinas, Brazil) The mechanical properties of amorphous thin films clearly depend on their chemical composition and structure. In this work, amorphous hydrogenated carbon films containing different proportions of nitrogen were fabricated using Plasma Chemical Vapor Deposition in a vacuum chamber fitted with a radiofrequency-excited (13.56 MHz) cathode and a substrate-holder to which a pulseable bias could be applied. The films were deposited from benzene, nitrogen, argon mixtures, the proportion of nitrogen in the chamber feed, RN, being varied from 0 to 50%. Structural and compositional analyses of films grown at different RN were obtained by infrared reflectance-absorbance and x-ray photoelectron spectroscopies. Nanoindentation was employed to determine the Young's modulus and the hardness of the films as a function of RN. The dependencies of the mechanical properties on RN are traced and discussed. Surface energy and contact angle measurements were also made. Greater nitrogenation favors greater contact angles.
DP-1-32 Non-hydrogenated Carbon Amorphous Prepared by RF Plasma Enhanced Chemical Vapour Deposition (PECVD) E.F. Motta, I. Pereyra (Escola Politécnica da USP, Brazil) Research on tetrahedral amorphous carbon (taC), is still at a young stage, in the sense that film preparation and characterization as well as practical applications have yet to be proven. In this way, the relationship between the deposition conditions, the growth mechanisms, the microstructure and the electronic density of states of films prepared by PECVD from hydrocarbon gaseous precursors are not fully understood. Therefore, in this work, we perform a systematic study by means of several complementary techniques to determine the correlation of the material microstructure and optical properties with the deposition conditions for taC samples deposited by radio-frequency glow discharge from methane and argon gaseous mixtures at 25°C. The studied deposition parameters were the plasma Rf power, the deposition pressure and the argon flow rate.
DP-1-33 Gas Permeation Through Polymer Membranes Modified by a C:H(N) Films Deposited Using Butene, Butadiene and Nitrogen Gas Mixture C.A. Achete, E.F. Castro Vidaurre, R.A. Simo, AC Habert (COPPE/UFRJ, Brazil) Pure amourphous hydrogenated carbon (a-C:H) and amorphous nitrogen incorporated (a-C:H(N)) films, with thickness up to 1 mm, were deposited onto asymmetric porous substrates of polysulfone (PSf) membranes by 13.56 MHz r. f. self bias glow discharge using pure Butadiene, Butene or mixtures with nitrogen. Several deposition parameters, namely bias voltage (Vb) , nitrogen partial pressure (PN) and total pressure P, were varied in a controlled way. The permeation of the gasesN2, and CO₂ was measured and the reduction of the permeability coefficient was correlated to composition and structure of the a-C:H(N) films obtained with different gases. The stoichiometry of the layers was analyzed using ion-beam techniques on films deposited onto silicon samples. The surfaces were analyzed using optical microscopy and atomic force microscopy (AFM). Room temperature conventional gas permeation measurements were performed on uncovered membranes and as a function of film thickness for layers deposited with different gases, Vb and PN. It was observed a general tendency of reduction of the permeability coefficient with the film thickness, reaching a minimum reduction of 95% for polymerlike layers of about 100 nm. Surprisingly, the barrier efficacy of the coating decreases with increasing a-C:H(N) film thickness or increasing bias voltage. This unexpected result is attributed to both, appearance of a network of cracks on the hole surface of the coating and the severe etching of the membrane surface during the deposition.
DP-1-34 Blood Compatibility of Diamond-Like-Carbon Films: Effects of Physical Properties P. Yang (City University of Hong Kong); N. Huang, J.Y. Chen (Southwest Jiaotong University, China); Y. Leng (Hong Kong University of Science & Technology); P.K. Chu (City University of Hong Kong) Diamond-like-carbon (DLC) films have received much attention recently and applications are being developed to take advantage of their good biocompatibility, for instance as biomaterials in blood contacting-devices such as rotary blood pumps, mechanical heart valves, coronary artery stents, and so on. However, the blood compatibility mechanism of the materials is not well understood. In this work, we focus on the relationship between the film physical properties and blood compatibility. Diamond-like carbon films are fabricated on different substrates at room temperature using plasma immersion ion implantation and deposition (PIIID). By adjusting the deposition process parameters, we obtain a series of DLC films with different physical and chemical structures. The blood compatibility of the films is evaluated in vitro platelet adhesion tests. The adhesion, activation, and morphology of the platelets are investigated using scanning electron microscopy (SEM). The film physical properties and surface characteristics are examined, including the semiconductor property parameters and surface wettability. The results provide insights in the blood compatible mechanism of DLC films.
DP-1-35 Effect of High Pressure in Diamond Anvil Cell on Carbon Thin Films. L.K. Shvedov, O.G. Lysenko, O.M. Kutsay (Institute for Superhard Materials, Ukraine) The deformation of materials in DAC is a widely used method to study different physical and chemical phenomena in materials. Information about mechanisms of high-pressure action on thin carbon films is necessary to better understanding in mechanics of phase transformations and relaxation of intrinsic stresses in carbon materials. A new technique and apparatus using X-ray and acoustic emission analysis to study of thin films under high pressure was developed. The carbon films were deposited from RF-discharge plasma (operating frequency being 13.56 MHz) in a capacity type reactor. Structural changes and phase transformation in carbon films at pressure up to 50 Gpa and room temperature have been studied. Experiments have shown decreasing in intrinsic stresses of thin films after high-pressure action.
DP-1-36 Growth of Nanocrystalline Diamond Films by Hot Filament Chemical Vapor Deposition Using CCl₄/H₂ Gases C.H. Ku, T.-C. Wong, J.-J. Wu (National Cheng Kung University, Taiwan, ROC); C.T. Wu, K.H. Chen (Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan); L.C. Chen (National Taiwan University, Taiwan, ROC) Nanocrystalline diamond films have been successfully deposited at 550°C using CCl₄ as carbon source in a hot filament chemical vapor deposition reactor. Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) were employed to characterize the surface roughness and the structure of the films. The crystalline size of the diamond films could be reduced by either increasing the CCl₄ concentration or increasing the filament temperature. The roughness of the nanodiamond film (rms) determined by AFM could be as low as 6 nm. The TEM results indicate that a uniform film with an average crystal size less than 50 nm was formed using 2.5 % CCl₄ at a filament temperature of 2000°C. All d values calculated from the selection area diffraction patterns can be indexed as those of diamond. Moreover, the high resolution TEM images of the nanodiamond film reveals that in addition to the diamond structure represented by the diamond lattices, the fragmental onion-like structures also appear within the film. The characterization of the growth of nanodiamond films and further EELS bonding analyses of the fragmental onion-like structures within the film will be presented in this paper.
DP-1-37 Characterization of the Crack-Paths and Fracture Resistance of Chemically Vapor Deposited Diamond Thin Films H. Takahashi, S. Kamiya, M. Saka, H. Abé (Tohoku University, Japan) Ever since chemical vapor deposition (CVD) methods were developed, polycrystalline diamond films have attracted increasing attention because of its superior properties. In many kinds of application, the excellent properties of diamond are expected to bring significant advantages. However, the applications of CVD diamond films are still limited due mainly to their weak mechanical strength, especially their brittleness. CVD diamond films could be considered as a kind of polycrystalline ceramics, therefore the crack extension resistance would be strongly dependent on their characteristics of crystal grain orientations and grain boundary structures. The crack-paths in CVD diamond films were extensively surveyed in this report over a variety of films with different crystal grain structures which could be obtained by changing the deposition conditions in microwave plasma enhanced CVD. Transmission electron microscopy as well as scanning electron microscopy revealed that distinctive deviation of microscopic crack extension could be observed when the film had a specific structure. This fact would suggest a potential to significantly enhance the macroscopic crack extension resistance. Fracture toughness of these films was quantitatively measured by a new technique developed by the authors. The possibility for the development of super-tough diamond films would be further discussed from the view point of positive control of deposition condition.
DP-1-38 Diamond Coating Of Blade Cutting Edges V. Baranauskas (University of Oxford, United Kingdom); A.C. Peterlevitz, H.J. Ceragioli, S.F. Durrant (Universidade Estadual de Campinas, Brazil) The nucleation, structural defects, crystalline structure and growth mechanisms of diamond fabricated by chemical vapor deposition are directly related to the geometry of the substrate surface. These parameters are usually studied for planar or flat substrates, where there is competition for space between neighboring grains, inhibiting growth in their preferred crystalline direction, which often results in columnar structured materials. In this work, we focus our attention on diamond growth upon substrates with very sharp surfaces, such as blade cutting edges. Our objective is to discuss the nature of the columnar structure and the possibilities of obtaining adherent diamond films on steel and silicon. Critical discussion of experimental analyses of the samples by transmission and scanning electron microscopies and micro-Raman spectroscopy is given.
DP-1-39 Effective Thinning Free-standing Diamond Films by Plasma Diffusion Etching Process S.-H. Kim (Silla University, South Korea); T.-G. Kim (Miryang National University, South Korea); E.-J. Bae (Pusan National University, South Korea) We placed the free-standing diamond film between the metal (or the metal alloy) and the Mo substrate like a metal-diamond-moybdenum (MDM) sandwich. We set the sandwich-type MDM in a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system. The sandwich-type MDM was heated over ~ 1,273 K by using the hydrogen plasma. Planarization of the free-standing diamond film surface as smooth as possible could be obtained by using the hydrogen plasma etching with the diffusion of the carbon species into the metal or its alloy. After etching the free-standing diamond film surface, we measured surface roughness and morphologies as a function of the metal. The incorporated impurities on the etched diamond film surface were also investigated. Detailed processes to obtain a very fine etched state of the diamond film surface, the characteristics of the etched area, and the reason for the enhancement of the etching efficiency are presented and discussed.
DP-1-40 Progress In The Fabrication Of Porous Diamond V. Baranauskas (University of Oxford, United Kingdom); H.J. Ceragioli, A.C. Peterlevitz, S.F. Durrant (Universidade Estadual de Campinas, Brazil) The wide range of technological applications of diamond stems from its unique properties such as chemical inertness, high thermal conductivity, great hardness, and low coefficient of friction. The thrust of most experimental and theoretical research efforts, however, is directed towards the production and understanding of bulk crystals or solid films. Porous diamond is a material of potential interest for molecular filters, field emission devices, photonic band-gap devices, and so on. Here we discuss progress in the development of methods of fabrication of porous diamond. We compare novel techniques for the production of porous diamond, such as the addition of noble gases to the reactor feed, or the use of porous silicon or natural fibers as templates for diamond growth. Results are discussed in terms of growth mechanisms and texture, porosity, and strength. Morphological data obtained by scanning electron microscopy (SEM) and results from Raman spectroscopic analyses are also presented.
DP-1-41 Electron Paramagnetic Resonance Centers in Combustion-deposited Diamond Films Subjected to High Gamma Radiation Levels L.M. Apatiga (Universidad Nacional Autonoma de Mexico); D. Mendoza-Anaya, F. Urena (Instituto Nacional de Investigaciones Nucleares, Mexico); A. Castaneda-Miranda, V.M. Castano (Universidad Nacional Autonoma de Mexico) Electron paramagnetic resonance centers in combustion-deposited diamond films were studied at 9.5 Ghz. The films were subjected to high doses of gamma radiation, ranging from 0.3 to 1.2 kGy, at room temperature. High quality diamond films with a ve ry low non-diamond carbon content were used in this study, previously deposited at 800 °C on molybdenum substrates by the combustion flame technique, using an oxygen/acetylene gas mixture. The EPR spectra reveal well-defined nitrogen and hydrogen-re lated d efect states on the diamond surface, due to the growth conditions and to the deposition zone, which is highly enriched in hydrogen and carbon monoxide. The concentration of EPR centers is highly sensitive to the gamma radiation. At g=2.0028 th e EPR intensity decreases, for a given dose, from 0.3 to 0.9 kGy and increases at 1.2 kGy. This behavior suggest a H-terminated diamond surface as well as the well-defined sbstitutional nitrogen defect states on the diamond network. Confocal micro Raman spectroscopy and scanning electron microscopy were also used to characterize the diamond films. Ë‡.
DP-1-42 New Method for Surface Modification and Hard Coatings A. Torosyan (National Academy of Sciences, Armenia); M. Becker, T. Schuelke (Fraunhofer USA) A new approach to modify metal surfaces and deposit hard coatings is introduced. It is well known that the improvement of surface quality and its activation are integral parts of many deposition techniques. It has also been established that the mechanical impact processing of solids with milling balls significantly activates solid surfaces by increasing the speed of chemical interactions. Moreover, the residual compression acts to inhibit crack growth, improves wear properties, and prolongs fatigue life of components treated in this way. The high degree of hardening and low roughness of the substrate surface achieved at this stage leads to a better quality of the resulting coatings. The method discussed in this paper is based on the in-situ mechano-chemical processing of the substrate and the formation of hard coatings. All these processes take place at room temperature, making them attractive to coat low-alloy aluminum and steel components. As an interesting example of surface modification, namely its purification and hardening, the mechano-chemical processing of low-carbon containing steel substrates in organic solvents and its doping with carbon was chosen. Simultaneously, the deposition, characterization, and application of diamond containing Al_xO_x micro-composite films are presented. The latter system was selected due to its superior adhesion and mechanical properties. Some mechanical properties of the modified layers and formed coatings were identified by means of strain-strength and micro-hardness tests. It has been shown that mechanical processing in reducing mediums by removing unwanted impurities brings significant improvements of the substrate micro-hardness. Laser-induced surface acoustic waves (SAW) have been used to determine the Young’s modulus of the film material.
DP-1-43 Field Emission and Structure Studies of Carbon Nanotubes In-situ Growing by Hot Filament Chemical Vapor Deposition C.-F. Chen, C-L. Lin, C.-M. Wang (National Chiao-Tung University, Taiwan, ROC) Carbon nanotubes have been considered the most promising material for electron field emitter due to their low turn-on field and high emission current. Otherwise, there are reports demonstrated the possibility to modify the properties of carbon nanotubes by integrating deposition and post heat treatment processes, which can be used for blue light emission applications. A modified hot filament chemical vapor deposition (HFCVD) which using the filament, Fe-Cr wire, acts as catalytic source and heat source has been developed to in-situ growing carbon nanotubes. This method can be considered as direct-syntheses, instead of catalytic coating on substrate. Carbon nanotubes were deposited on Si substrate with CO2, Ar and/or N2 as carrier gas through ethanol. The preliminary results show that various deposition parameters, such as carrier gas and flow direction to the substrate, affect the morphology and structure of the carbon nanotubes. Furthermore, we fabricated a novel light emission device using carbon nanotubes synthesized on silicon substrate as a cathode, and the ITO glass with a printed ZnO:Mn blue phosphor as an anode plate. This device involving gap structure between the cathode and the anode. The morphology and distribution of nanotubes were observed by SEM, the quality was analyzed by Raman spectroscopy, and the microstructure of nanotubes was characterized by HRTEM images. Finally, we used I-V measuring system to obtain the field emission characterization. Effects of deposition parameters on nanotubes structures and properties have been studied and the results will be presented.
DP-1-44 Low Temperature Growth of High Yield Multi-walled Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition Using CH₄ and CO₂ Gas Mixture M. Chen, C.-M. Chen (National Chaio-Tung University, Taiwan, ROC); C.-F. Chen (National Chiao-Tung University, Taiwan, ROC) The vertically-aligned carbon nanotubes(CNTs) with multi-walled structure were successfully grown on a Fe-deposited Si substrate at low temperature below 300°C by using the microwave plasma chemical vapor deposition of methane and carbon dioxide gas mixture. That is apparently different from the conventional reaction in gas mixtures of hydrogen and methane, hydrogen and acetylene, and hydrogen and benzene..etc for the formation of diamond and carbon nanotubes. After deposition, the microstructure morphology of carbon nanotubes was observed by using scanning electron microscope and high resolution transmission electron microscopes. The characteristics of CNTs was analyzed by laser Raman spectroscopy. The results showed that a vertically aligned carbon nanotubes with the diameter of about 15nm and multiwalled were illustrated by SEM and HRTEM However, the highest yield of carbon nanotubes in about 50% was obtainted at low temperature below 300°C by MPCVD using the CH₄-CO₂ gas mixture of properly controlled parameters.
DP-1-45 Correlation of Microstructural and Mechanical Properties with the Biological Acceptance of Diamond-like Carbon Coatings A. Dorner-Reisel (Freiberg University of Mining and Technology, Germany); C. Schürer (Chemnitz, Institute of Physical and Mechanical Technologies, Germany); E. Müller (Freiberg University of Mining and Technology, Germany) Diamond-like carbon coatings are suitable materials for the surface finishing of implants. These coatings exhibit a bioinert behaviour, which can be further modified and tailored by doping the DLC with appropriate elements. Due to the chemical resistance and the low permeability of DLC, these coatings are applied as corrosion protection and diffusion barrier on metallic implants successfully. With this, the so called metallosis is prevented, which is a negative tissue reaction of the living body caused by the release of metallic ions. Low friction coupled with outstanding wear resistance are properties of DLC, which obtain significance for surface finishing of joint prostheses. Due to the harsh mechanical and tribological loading of such prostheses, a sensitive adjusting of the nano- and microstructural features is essentially. Current research focuses on the generation of nano- and microstructures, which improve both biocompatibility and -functionality of metallic and ceramic prostheses. The mechanical data of DLC coatings are investigated and correlated to the coatings nano- and microstructure. Additional emphasise is given to the characterisation of the biological acceptance of the DLC. Cell culture test were carried out with mouse fibroblasts of the type L929 and give evidence of different biocompatibility of the coatings.
DP-1-46 Small-scale Mechanical Property Testing of Thin Films at Elevated Temperatures J.F. Smith, B. Beake, S.R. Goodes (Micro Materials Limited, United Kingdom) Small-scale indentation and scratch testing of thin films is normally carried out at room temperature, even when the films are actually used at higher temperatures. The potential pitfalls in extrapolating room temperature data in this way are obvious. Hitherto, room temperature testing has been preferred simply because of the difficulties in using highly sensitive displacement measuring instruments in a stable fashion across a temperature range. To remedy this, a depth-sensing indentation instrument has been adapted for operation at temperatures exceeding 500°C. With this apparatus, thermal drift rates of less than 0.01 nm/s have been achieved, even at the highest temperatures. For the first time, therefore, it has been possible to study, at widely different temperatures, the behaviour of thin films subjected to a variety of mechanical operations. Several thin film + substrate structures and bulk material surfaces have been investigated, in several cases at 500°C. The particular techniques used were: (i) indentation for hardness and modulus determination, (ii) scratch testing for adhesion determination, and (iii) impact testing. As anticipated, in some cases temperature was found to be an extremely important testing parameter, with temperature variation resulting in substantial property changes.
DP-1-47 The Control of Grain Size in Process of CVD Diamond Growth T.B. Huang, A. Fernandes, V. Neto, J. Gracio (University of Aveiro, Portugal) Diamond coatings are attractive for potential application owing to their extreme properties. Mechanical applications of diamond coatings need to produce films with controlled grain size. Growth diamond films by chemical vapor deposition (CVD) includes a complex reaction in which a hydrocarbon gas mixed in low concentrations with hydrogen is energized thermally or in a plasma prior to contact with a heated substrate. In conventional CVD process, the reaction gases are kept at a constant rate. As a result of growth competition, some diamond crystals with preferential orientation become larger and larger with the growth evolution. The films therefore exhibit non-uniform structure along the profile. Furthermore, the surface roughness has been shown to be proportional to the size of diamond crystals and consequently many applications may be limited by a rough surface. One of the essential growth characteristics of CVD diamond is the column structure appearing after an initial growth stage. The growth competition between the diamond crystals leads to gradual increase in the crystal size along the film profile. This phenomenon is considered as a result of very few secondary nucleation sites during the crystal growth. Such a variation in the microstructure and morphology is usually undesired. For instance, a electrical conductivity and defect concentration include contributions from both the diamond grains and the grain boundaries, the non-uniform structure along the profile leads to a change in the ratio of grain/grain boundary, making the film properties uncertain. The experiments reveal that the grain size of diamond crystals can be controlled well by process parameters. A short beginning stage is applied with relatively higher concentration of hydrocarbon. The subsequent stage is applied with low concentration hydrocarbon. The above process is effective to control the grain size. In addition, the concentration of other gases can affect the grain size.

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