Papers

ICMCTF2004 Session DP: Symposium D Poster Session

Thursday, April 22, 2004 5:00 PM in Room San Diego

Thursday Afternoon

Time Period ThP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2004 Schedule

DP-1 Synthesis of Light Emitting Β-FeSi₂ Nano-dots on Si_0.8Ge_0.2 Y.L. Chueh, L.J. Chou, W.W. Wu, J.H. He, S.L. Cheng (National Tsing Hua University, Taiwan, R.O.C.); L.J. Chen (National Tsing Hua University, Taiwan, ROC) The formation of β-FeSi₂ quantum dots has been extensively studied, mainly because it has many merits such as less temperature fluctuation, low threshold voltage and high emitting gain. In present study, the beta-FeSi₂ quantum dots were formed on Si_0.8Ge_0.2 by interposing different thickness of amorphous-Si or epi-Si layer. The microstructure of the beta-FeSi₂ quantum dots were investigated by TEM, indicating that two different epitaxial relationship were found in between dots and substrate. The Strong photoluminescence (PL) peak at 0.81 eV was observed at 13 K for β-FeSi₂ nanodots grown on epitaxial Si on Si_0.8Ge_0.2 substrate. In contrast, the PL of polycrystalline beta-FeSi₂ nanodots grown on Si_0.8Ge_0.2 with a sacrificial amorphous Si layer was not evident. The measured PL peak is attributed to the electron-hole pair recombination in β-FeSi₂ nano-dots.
DP-2 Characterization and Formation of Nanocrystalline Diamonds in A-C:N Films by 90°-bend Magnetic Filtered Cathodic Vacuum Arc Plasma W.J. Hsieh, P.S. Shih, C.C. Lin, U.S. Chen, Y.S. Chang, H.C. Shih (National Tsing Hua University, Taiwan, R.O.C.) Nitrogen incorporated diamond-like carbon (a-C:N) films were deposited on silicon (111) wafers using a 90°-bend magnetic filtered cathodic arc plasma system. The structure and properties have been studied by TEM, glancing incident X-ray diffraction, SEM, ESCA, Raman, and FTIR. For the a-C:N film depositions a highly ionized energetic plasma was used to produce carbon ions with varying ion energies to form various carbon bondings in the film. The ion energy can be enhanced by applying a bias voltage to the substrate. Our previous work indicated that the DLC films can have a higher hardness with a substrate pulsed bias between 100V to 350V, and a maximum sp³ bonding content at a pulsed bias of 350V according to the result of ESCA. In this study a-C:N film shows a higher fraction of sp³ bonding contents due to nanocrystalline diamond clusters formed in the a-C:N film. The nitrogen content was also found to increase with increasing substrate bias voltage. However, the graphitization of the a-C:N film increases with the annealing temperature that causes a sudden loss of the sp³ bonding. The maximum incorporation of nitrogen to the a-C:N film is up to N/C=0.38(ESCA) using the 90°-bend magnetic filtered cathodic arc plasma system.
DP-3 The Proof of SLS Mechanism C.Y. Wang, H.C. Shih (National Tsing Hua University, Taiwan, R.O.C.) The SLS growth mechanism of synthesizing Si nanowires is detailed expressed by analyses of the catalyst structure and the nanowire composition. A thin catalyst layer of platinum ~5nm is first sputtered on the silicon wafer, the solid silicon source for nanowires. The platinum collapses into dots with diameter about hundreds of nanometers due to the stress during the heating in the furnace. SEM and SAD analyses show these dots transform into crystalline Pt₃Si with the substrate and serve as nucleation seeds for nanowire growing. Because of the high process temperature (~1100°C) and long duration time (~5hr), the silicon wafer transforms into amorphous silicon oxide and melts into the platinum silicide catalyst dots until saturation to form amorphous SiOx nanowires characterized by TEM and EELS. The SiOx nanowire is ~40-60 nm in diameter and several hundreds of micrometers in length.
DP-4 Preparation of Ni-Filled Carbon Nanotubes for Key Potential Applications in Nanotechnology E. Titus (University of Aveiro, Portugal); P.K. Tyagi, M.K. Singh, A. Misra, D.S. Misra (Indian Institute of Technology Bombay, India); N. Ali, J. Gracio (University of Aveiro, Portugal) Chemical Vapour Deposition (CVD) is now a well-established route to the growth of carbon nanotubes. Generally, a transition metal such as nickel dispersed as clusters on a non-reactive substrate acts as a catalyst for growth from carbon-bearing gases such as methane. Catalysis is a potentially powerful tool for controllable synthesis, for the selective production of carbon nanotubes either concerning diameter, wall thickness or simply well-crystallized structures, free of amorphous material. Zeolite materials are widely used as catalysts, absorbents and supports for catalysts. Hernadi et al first reported the use of zeolites (NaY, HY and ZSM-5) as catalyst supports to synthesize carbon nanotubes and the chemical separation of the formed carbon nanotubes from catalyst. Because zeolites are porous materials with regular crystal structures and pore arrangements, they are speculated to act differently from other solid materials. However, many aspects about catalytic production of carbon nanotubes using zeolite supports remain uninvestigated. Here we report a new technique of synthesis of carbon nanotube on Nickel /Zeolite substrate. HZSM-5 zeolite of pore size 5.7-5.8 was thoroughly mixed with nanosized (30-40nm) Nickel particle by fine grinding and was pressed in the form of a pellet of thickness 1mm. Depositions were carried out in hot filament chemical vapor deposition (HFCVD) system. The gas precursors for the depositions were CH₄ and H₂. The tubes were purified by acid treatment and oxidation 2. The characterization of the tubes by SEM, TEM and Raman spectroscopy techniques will be discussed in detail.
DP-5 Growth of Chromium Carbide Capped-carbon Nanotip using Bias-assisted Microwave Plasma Chemical Vapor Deposition C.H. Hsu, C.F. Chen, S.C. Shi (National Chiao Tung University, Taiwan, R.O.C.) Chromium carbide capped-carbon nanotips were synthesized using bias-assisted microwave plasma enhanced chemical vapor deposition. Such a material grew up to about several hundreds of nanometer long and tens of nanometer in diameter. Similar to the vapor-liquid-solid model of carbon nanotubes, the chromium nanoparticles were all lifted off during growth process. Accompany with the increasing tip length, the diameter also increase via vapor-solid transformation. It is also found that the growth of chromium carbide capped-carbon nanotips reaches a limit, which is due to the fully carburization of chromium that lost its catalytic behavior. The applied bias is also a significant parameter, that is, the higher bias is effective to increase the growth rate. However, the higher bias also contributes to a rapid formation of chromium carbide which leads to a shorter length of carbon nanotip at the same time. The higher ion energy also varies the tip diameter due to strong ion bombardment effect which is a competitor to deposition. The growth mechanism of chromium carbide-capped carbon nanotip is presented.
DP-6 Coating of SiC Surface by the Thin Carbon Films with Using of the Carbide-derived Carbon (CDC) Process A.V. Zinovev, J.F. Moore, M.J. Pellin, J. Carlisle, O. Auciello, J. Hryn (Argonne National Laboratory) The conversion of silicon carbide into carbon in helium-chlorine-hydrogen gas mixtures has been studied. Due to the more energetically favored reaction of Cl₂ with Si rather than C, the selective etching of SiC surface can take place, leading to the formation of a carbide-derived carbon (CDC) film. The results of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and SEM studies of single crystal SiC and industrial polycrystalline alpha-SiC, treated at different gas concentrations and different temperatures will be presented. XPS analysis of carbon C1s fundamental peak and valence band spectra show that CDC films are not phase pure but consist of a mixture of sp² and sp³ bonded carbon. A strong difference in the nature of the CDC process for different types of SiC materials (single crystal or industrial ceramics) was observed, which may be connected with different SiC grain boundary conditions and surface morphology effects in these materials.
DP-7 Effects of Catalyst Preparation on the Field Emission Properties of Carbon Nanotubes S.H. Lin, J.M. Ting (National Cheng Kung University, Taiwan, R.O.C.) Growth of carbon nanotubes (CNT) has been a subject that receives intensive research for more than 10 years. One of the important focuses is the preparation, and therefore the characteristics, of catalysts. Several methods have been used to prepare catalysts, leading to various characteristics. However, understanding the relationship between catalyst preparation and CNT's properties or performance desires additional studies. Furthermore, new potential catalysts remain to be explored. In this study, we have investigated the use of new iron alloys as the catalysts for the growth of CNT. The preparation of the thin film alloy catalysts and its effect on the field emission properties are addressed. The preparation is such that the resulting alloy catalysts exhibit different compositions, thickness, roughness, grain size, and crystallinity. The growth of CNT was carried out using a thermal chemical vapor deposition (CVD) method. The reaction gases were C₂H₂ and NH₃ with a fixed C₂H₂/NH₃ ratio. The growth time was 10 min approximately. CNT obtained was characterized for microstructure using micro-Raman and high resolution transmission electron microscopy (HRTEM), and subjected to field emission test at room temperature.
DP-8 Effects of Substrate-biasing on Structural and Field-emissive Properties of Carbon Nanotubes Synthesized by LCP-CVD Method C.K. Park, J.P. Kim, Y.D. Kim, H.S. Uhm, J.S. Park (Hanyang University, South Korea) Carbon nanotube (CNT) field-emitters are purported to be ideal candidates for the next generation of flat panel displays, microwave power amplifiers, and so on. Various methods have been utilized for the synthesis of carbon nanotubes. The CVD method has several advantages over the other methods, which includes low deposition temperature and control of diameters of the nanotubes grown. Furthermore, it is relatively easy to obtain vertically-aligned CNTs by increasing the nucleation density and growth rate. Recently, it has also been reported that controlling the plasma potential during CNT-growth by means of using substrate-biasing techniques may be helpful for the alignment of nanotubes grown and furthermore, of benefit to improve the quality of the CNTs. However, this issue has failed to be profoundly investigated. In this research, we present experimental results regarding the effect of substrate-biasing on structural and field-emissive properties of well-aligned multi-wall CNTs which are synthesized by inductively-coupled plasma-CVD (ICP-CVD). A patterned TiN film (150nm) is prepared on a SiO₂(200nm)/Si(100) substrate by DC magnetron sputtering. A Ni catalyst layer (5µm-diameter) is formed on the TiN layer by RF magnetron sputtering. Prior to growth of CNTs, NH₃-plasma etching is performed to improve the density and uniformity of nanosized Ni droplets. CNTs (1-2µm length) are subsequently grown using a gas mixture of C₂H₂ and NH₃ by varying the DC substrate bias voltages from -550V to 300V. Nanostructures and morphologies of the CNTs grown are analyzed by monitoring the results obtained from Raman spectroscopy, field-emission SEM, and high-resolution TEM. Nitrogen concentration in the CNTs has also been measured by AES, as a function of the bias voltage. For all the grown films, field emission characteristics are measured, which are also correlated with crystal structures, nitrogen concentrations, and morphologies.
DP-9 Metal-doped Diamond-like Carbon Films Synthesized by the Hybrid Filter Arc Evaporation and the Metal Plasma Ion Implantation Process K.W. Weng, Y.C. Chen, Y.C. Ho (Mingdao University, Taiwan, R.O.C.) In our previous researches [1,2], the metal-doped diamond-like carbon films (DLC) have been synthesized successfully using the cathodic arc evaporation (CAE) process and possess excellent mechanical properties. The interfacial gradient and the high surface roughness are inherent disadvantages of the conventional CAE-DLC process and limited itâ€™s application in precision industries. Nowadays, a novel particle-free DLC process has been designed. The powerful equipment is combined with the quarter plasma duct filter arc (FAD) and the MPII ion source. In the initial coating stage suitable carbon dose of 21017 atoms/cm² was implanted by MPII to activate the substrate surface and to improve the interface properties due to the appearance of the dispersive new carbide phase, supersaturation alloys and high dislocation density. During deposition process chromium target was used in the filter arc system and the working pressure was controlled at 2.0 Pa. The intense Cr plasma energy generated from the quarter plasma duct activated the decomposition of hydrocarbon source gas C₂H₂ to from the particle-free, denser structure and excellent mechanical properties metal-doped DLC. Absolutely to solve the nature disadvantages of the conventional CAE process and extend the application field not only in the cutting tools and furthermore can be used in the 3C industries.
DP-10 UV Stimulated Photo-catalytic Activity on Polycristallyne Diamond Film Surfaces L.M. Apatiga, V.M. Meneses (Universidad Nacional Autonoma de Mexico) A photo-catalytic reaction produced on polycrystalline diamond film surfaces by UV light was studied by micro Raman spectroscopy. The diamond films were specially prepared for this study by the Radio Frequency assisted CVD technique (RFCVD). The photo-catalytic activity was analyzed in terms of the sharpness of the typical diamond Raman band at 1332 cm^-1 and by the weak non-diamond carbon features around 1550 cm^-1. The micro Raman analysis shows a decrease of the non-diamond carbon content originally co-deposited on diamond film surfaces during the synthesis, which was proportional to UV irradiation time, suggesting that the photocatalytic reaction can be controlled by the UV dose. Since, a selective reduction of the non-diamond carbon phase was obtained on diamond surfaces. The UV irradiation was applied continuosly during 1, 2, and 3 days in open atmosphere at room temperature. The role of oxygen radicals, such as ozone and atomic oxygen on the photo-catalytic reaction is discussed, as well.
DP-11 Improvement of Cutting Performance with Diamond Coating by Boron Doping H. Hanyu (OSG Corporation, Japan); S. Kamiya (Tohoku University, Japan); Y. Murakami (OSG Corporation, Japan) Diamond has been used for cutting tools for many years, because of their significant advantage of abrasive resistant property due to their hardness. Especially, diamond coating, which has been developed in recent periods, has been showing excellent performance in the case of cutting with non-ferrous material and non-metal material, which shows very heavy abrasive properties. But by the reason that diamond is consisting of carbon, diamond has weakness against oxidation under high temperature atmosphere. Boron doped diamond is well known about its electric property. And it is also known the anti-oxidation properties could be improved by Boron doping. In this research, we tried to apply this Boron doped diamond coating to the rotating shaft tools to improve their cutting performance. In our research, first we tried to cut some kind of ferrous materials with endmills. In the case of cutting cast iron, we could recognize the advantage of Boron doping, and we could get better results than normal diamond. We could observe improved wear resistance much better than normal diamond in cutting cast iron. However, in the case of normal carbon steel, which has large property of diffusion of Carbon into their systems, we could observe better durability with Boron doped diamond than normal diamond, but the performance was not enough in comparison with normal abrasion resistant coating such as TiAlN. We also tried to cut the other kind of materials, and we could observe improved performance in the case of cutting non-ferrous material, which has high abrasive properties.
DP-12 Characterization of Titanium-containing Diamond Like Carbon Films Deposited by Cathodic Arc Evaporation P.C. Tsai (National Huwei Institute of Technology, Taiwan, R.O.C.); J.Y. Chiang, Y.F. Hwang (National Taipei University of Science and Technology, Taiwan, R.O.C.); W.J. Chen (National Pintung University of Science and Technology, Taiwan, R.O.C.) Titanium-containing diamond-like carbon films have been produced by mixing C⁺ and Ti⁺ plasma streams originated in cathodic arc plasma sources processed at substrate-bias voltage ranging from -50 to 300V. The characteristics of the films were investigated using Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and nanoindentation tester. The microstructures of the films were evaluated using field emission scanning electron microscopy (FEGSEM), X-ray diffractometry (XRD) and high-resolution transmission electron microscopy (HRTEM). The results showed that thick and well adhesive titanium-containing DLC films were synthesized on the substrate successfully by a Ti interlayer. The films reveal a layered structure and consist of DLC, TiC and TiO₂. The nanoindentation hardness of the films was between 8 and 12 Gpa. The roughness (Ra) of the films ranged from 2 to 8 nm. The effects of processing parameters on the deposition rate, sp³/sp² ratio, roughness, and nanohardness of the deposited films were evaluated. The XPS spectra of the films and high-resolution transmission electron microscopy (HRTEM) studies on the films will also be discussed.
DP-13 Synthesis of Multiple-junction Carbon Nanotubes using a Thermal CVD Method T.P. Li, J.M. Ting (National Cheng Kung University, Taiwan, R.O.C.) Due to their excellent properties, the use of CNT in molecular-scale or nanoscale devices is being extensively explored. This inevitably involves the creations of two-dimensional (2D) and three-dimensional (3D) junctions, which have been considered as the building blocks of nanodevices. Two-dimensional junctions were previously with or without the use of a template. In a previous study, we have obtained not only 2D but also 3D junction CNT using a thermal chemical vapor deposition (CVD) method without the use of any template. However, the mechanism for the growth of multiple-junction CNT is not known. In this study we have therefore investigated the growth mechanism by addressing the role of crystal orientation of the catalyst. The substrate used was silicon which was subjected to scratching prior to the growth of CNT. CNT were grown in a thermal CVD chamber using various mixtures of CH₄ and H₂. The growth temperature was also varied. The CNT obtained were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Correlation between the crystal orientation and the splitting direction of CNT was made. A growth mechanism based on such a correlation is discussed. Keywords: CNT, Multiple junction, Catalyst.
DP-14 Comparative Study of Amorphous Hydrogenated Carbon Films Produced from Methane, Butane, Butadiene C.A. Achete, P.J. Araujo, R.A. Simao (Universidade Federal do Rio de Janeiro, Brazil); C.M. Lepienski (Universidade Federal do Parana, Brazil) Amorphous hydrogenated carbon (a-C:H) films and its alloys are being successfully used opptical filters, protective layers semiconductors and also as a barrier against permeation and in polymers superficial modification in order to produce liquid-gas separation membranes. However, the residual stress is still a serious problem to be solved to improve the quality of the system. In the present work a-C:H were produced by glow discharge at the radio frequency of 13,56MHz using the following gases: Methane, Butane, Butadiene. This technology can be used with membranes, polymers surfaces, mechanical tools, surfaces needing protective coatings such as fibers and optical "things". Different self-bias were used in order to investigate its influence on the produced films. Pieces of silicon (100) were used as substrate. The nano hardness was measured by nano identation technique and related to the applied self-bias. Films that present high values of residual stress can have cracks. Different values for the residual stress, nano-hardness were obtained by changing the work gas. The a-C:H films thermal stability was measured by the gas effusion technique. The nano-structure of the films as its frictional coefficient was analyzed by he atomic force microscopy (AFM).
DP-15 Nucleation Behavior during Initial Stage in Sublimation Epitaxy of SiC Films on 6H-SiC (0001) Substrate S.H. Seo, J.S. Song, M.H. Oh (NeosemiTech Corporation, South Korea); J.S. Park (Hanyang University, South Korea) The epitaxial silicon carbide (SiC) layer grown by sublimation epitaxy method is considered to be one of wide band-gap materials promising for high-temperature and high-voltage power electronic device applications and optical sensors in the ultraviolet region. High growth rate of SiC layer is necessary for development of various SiC-based devices in the industrial issue. In typical CVD process, the epitaxial growth rate is below 2µm/h, but the growth rate by sublimation epitaxy is higher than that for typical CVD. A sublimation method has generally been applied for SiC single crystal because this shows high growth rate of few hundreds to thousands micrometer. The SiC substrate and source for growth are simultaneously settled into high-purity graphite crucible. Accordingly, the unwanted nuclei can be formed on SiC substrates during the initial stage of raising temperature. (e.g the growth-induced defects and unwanted polytypes such as 3C, 4H, 6H and 15R are available to form in initial nucleation stage as a function of rising time for temperature, pressure and decompression rate.) However, there have scarely been reported on the systemically microscopic and spectroscopic evaluation on the nucleation behavior of epitaxial SiC layers grown on 6H-SiC (0001) substrates by sublimation epitaxy with various process conditions. In this research, we tried to clarify the nucleation behavior during the initial stage as a function of working pressure, decompression rate for gas, temperature and rising time until the wanted temperature and to suggest the optimized process conditions for high-quality SiC-epitaxial layer through various analyses. The SiC nuclei were formed in the temperature range from 1700 to 2240°C and pressure range from 5 to 50 Torr on 6H-SiC (0001) of on-axis. The rising time until 1700 to 2240°C and the decompression rate of working pressure during temperature-rising stage were performed for comparison of nucleation behavior. The nucleation density was decreased with process temperature increased. The island (3D-nulei : island growth mode) formation was increased with temperature increased and the step-growth (layer growth mode) behavior on surface was conspicuously revealed as process temperature increased. The nuclei formed at 1700°C were a coalescence of many triangular nuclei. With temperature increased, also, the nuclei were transformed from the coalescent triangular plate to the plateau. Raman spectra of SiC nuclei formed at the relatively low temperature of 1700°C exhibit the 3C polytype characteristics accorded with triangular shape of 3C (111) face at near 796.2 cm-1, while the nuclei formed at the relatively high temperature of above 2000°C show very weak spectra related to 3C. It should be noted that the 3C polytype was transformed to 6H at high temperature. Furthermore, the analysis data of the crystallographic and spectroscopic properties on the nucleation behavior are presented through employing high-resolution XRD, RHEED, photoluminescence, AFM techniques with micro-Raman data to elucidate the nucleation behavior.
DP-16 Hard Conductive a-C and a-C:H films Prepared by Magnetron Sputtering H.S. Myung, Y.S. Park, B. Hong, J.G. Han (SungKyunKwan University, South Korea) In recent carbon nitride (CN_x) films have been a subject of great interest due to high hardness, high elastic modulus and low friction coefficient, etc. These films can be synthesized by several techniques, such as chemical vapor deposition, ion beam deposition, arc ion plating, laser ablation and sputtering. Among these techniques, closed-field unbalanced magnetron sputtering has a lot of advantages such as process simplicity and control, film homogeneity and high deposition rate. In this study, therefore, carbon nitride films were synthesized by closed field unbalanced magnetron sputtering (CFUBM) to increase deposition rate and physical properties. Film structures and physical properties of carbon nitride were investigated as a function of nitrogen partial pressure. The film structures were investigated in Raman spectroscopy and FTIR. The mechanical properties of carbon nitride films were evaluated by nano indentation test and wear test.
DP-17 Optimisation of the New Time-Modulated CVD Process using the Taguchi Method N. Ali, V.F. Neto, S. Mei, J. Gracio (University of Aveiro, Portugal) In this paper, we report key findings relating to the deposition of polycrystalline diamond films onto silicon wafers using our newly developed time-modulated CVD (TMCVD) process. This new process was designed to render greater independent control, during film growth, over key film properties, such as morphology, crystallite size, surface smoothness, etc, in producing nano-sized diamond film coatings for biomedical, optical and mechanical applications. In this investigation, we employ the renowned taguchi technique to optimise the TMCVD process for preparing micro- and nanocrystalline diamond film coatings. The taguchi method for process optimisation is very efficient and cost effective since it reduces, considerably, the total number of experiments required during process optimisation and manufacturing. For the taguchi calculations, five parameters and five variables were considered for the analysis. Key process parameters, such as methane pulse cycles, modulations times, substrate temperature and deposition pressure, were varied accordingly during the taguchi analysis. In total, 16 experiments were performed, in accordance with the taguchi technique. All the film samples were characterised for microhardness, surface smoothness, growth rate, electrical resistivity and film morphology. The results were tabulated and additional graphs were constructed from the tabulated data in order to observe the trends. The data generated graphs enabled the selection for the optimum parameters. The as-grown film coatings were characterised for microstructure and morphology using SEM, XRD and AFM analysis, and for film purity using micro-Raman spectroscopy.
DP-18 Structure and Properties of Nanocomposite WC-C Films Deposited by a Hybrid Process of Ion-beam Deposition and DC Magnetron Sputtering A.Y. Wang, T.Y. Kim, K.R. Lee (Korea Institute of Science and Technology, South Korea) W-containing diamond-like carbon films were prepared on silicon (100) wafer by a hybrid deposition system composed of an end-hall type hydrocarbon ion gun and a DC magnetron sputter source of W. W concentration in the film could be controlled by changing the C₆H₆ fraction of the mixed Ar/C₆H₆ sputtering gas. Residual stress, hardness, elastic modulus and electrical resistivity were investigated as a function of W concentration. Raman spectroscopy, XRD and high resolution TEM were employed to characterize the microstructure of the deposited films of various W concentrations. It was shown that the films consisted of nano-sized WC particles embedded in an amorphous hydrocarbon matrix and were nanocomposite thin films at a higher W concentration. The mechanical properties of the films were discussed in terms of the spatial distribution of the WC particles.
DP-19 Cutting Force and Wear Evaluation in Peripheral Milling by CVD Diamond Dental Tools R. Polini (Universita' di Roma Tor Vergata, Rome, Italy); S. Guarino, F. Quadrini (Universita' di Roma Tor Vergata, Italy); H. Sein, W Ahmed (Manchester Metropolitan University, United Kingdom); A. Allegri (Universita' di Roma Tor Vergata, Italy) Co-cemented tungsten carbide (WC-Co) tools are currently employed in dental application for prosthesis fabrication. The deposition of a diamond coating would allow both to increase the tool life and to machine abrasive materials at higher speeds. However, at present it is very difficult to quantify the effective advantage of the application of a diamond coating onto dental tools compared to traditional uncoated tools. Therefore, in this work, we have deposited diamond coatings onto WC-Co dental tools having different geometries by Hot Filament Chemical Vapour Deposition (HFCVD). Prior to deposition, the WC-Co tools were pre-treated in order to roughen to surface and to modify the chemical surface composition (H. Sein et al., ICMCTF 03). The use of the HFCVD process allowed to deposit a uniform coating despite the complex geometries of the dental mills. For the first time we have studied and compared the cutting behaviour of both virgin and diamond coated dental tools by measuring both wear and cutting force time evolution under milling a very hard Co-Cr-Mo dental alloy (by DEGUSSA). To ensure constant cutting rate (20.000 r.p.m. cutting rate, 0.01 m/min feed rate and 0.5 mm depth of cut), a proper experimental apparatus was used. Three different mill geometries were considered in both coated and uncoated conditions. The results showed that, under the high speed conditions here employed, uncoated tools underwent to catastrophic failure within few seconds machining. Diamond coated tools exhibited much longer tool lives. Lower forces were measured when the coated tool is employed due to the much lower material-mill friction. The best behaviour was observed for coated mills with the presence of a chip-breaker.
DP-20 Characteristic of Carbon Nanotubes Deposition by Atmospheric Pressure PE-CVD C.W. Kim, Y.H. Lee, S.J. Kyoung, G.Y. Yeom (Sungkyunkwan University, South Korea) In the industrial plasma processes, low-pressure plasmas are dominant in the processing of the materials such as thin film deposition, etching, and surface treatment. However, to generate plasmas at low pressures, costly vacuum equipment and vacuum measurement tools are required, and the use of vacuum in the processing increases the fabrication cost and decreases throughput. If stable glow discharges can be realized under atmospheric conditions in large area, the expensive vacuum equipment and the measurement tools can be eliminated and the throughput can be also increased. However, if it used to be, also it discharged stabilize the plasma at atmospheric pressure, it will more advantage than low pressure about throughput, and cost. Especially, Carbon nanotubes (CNTs) are grown at low pressure. If we can grow CNTs at atmospheric pressure, processing cost and time can reduce. Already many people studied characteristic of atmospheric, so we tried application of atmospheric pressure plasma for growth of CNTs. In this study, we tried to grow of CNTs by the atmospheric pressure plasma. The CNTs were grown by using capillary electrode discharge of acetylene (C₂H₂) and ammonia (NH₃) at atmospheric pressure, we obtained 30nm multi-layer CNTs. The structure and morphology of product was analyzed by a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a Fourier transform Raman spectrometer (FT-Raman). This study provides a new method at atmospheric pressure and low temperature, which has some specials advantages for scale-up production or applications.
DP-21 Effect of Thermal Annealing and Ultraviolet Light Irradiation on Amorphous Carbon Nitride Films by RF-pecvd E.F. Motta, I. Pereyra (Universidade de Sao Paulo, Brazil) The deposition of amorphous nitrigen-carbon alloys has received particular attention since the theorical prediction of metastable carbon-nitride-like phase, i.e., C₃N₄. Extensive experimental efforts had been made on the preparation of carbon nitride using DC/RF sputtering and Plasma enhanced chemical vapor deposition (PECVD), which is one of the most widely used techniques. One of the difficulties encountered with PECVD as well as with other processes is to obtain films with the required 3:4 C/N atomic ratio. In this study, the changes in density, composition and structure of CN_x films induced by heat treatments as well as that of UV light irradiation were investigated. Raman scattering and Fourrier transform infrared (FTIR) spectroscopy were used to investigate the structural modifications, while the composition and chemical bonding in the CN_x films were analyzed by X-ray photoelectron spectroscopy (XPS). The fraction of sp² cluster decreases for increasing UV irradiation time and leads to an increase of the optical band gap. The thickness decreased for all annealing time suggesting increasing material density.
DP-22 Characterization of Nitrided Stainless Steel Coatings Deposited on Steel Substrate by Reactive DC-magnetron Sputtering G. Terwagne, J, Colaux (Universitaires Notre-Dame de la Paix, Belgium); D.R. Mitchell, K.T. Short (Ansto, Australia) Stainless steel coatings were deposited on low carbon steel and mono-crystalline silicon substrates by DC-magnetron sputtering in a reactive atmosphere containing argon and nitrogen. As the deposition process should be applied for industrial applications, the substrates were grounded and not heated during the deposition. The nitrided stainless steel coatings were studied from the structural and tribological point of view. The preferential orientation (111) and/or (200) of the layers associated with a column-like morphology underlined by X-Rays diffraction and transmission electronic microscopy is related to the thermal history of growth of the coatings. An evolution of the magnetic properties according to the atomic nitrogen concentration integrated within the layers is revealed by means of Massbauer spectrometry and magnetic force microscopy. Interstitial nitrogen atoms are homogenously distributed in the fcc array of austenitic steel (LEEIXS).
DP-23 Micro Processing of Thick DLC Films using by the Focused Ion Beam Techniques A. Tanji, S. Takeuchi, H. Noguchi, K. Mastuno, M. Murakawa (Nippon Institute of Technology, Japan) A DLC (Diamond-Like Carbon) film generally includes problems such as low adhesion strength i.e., easiness of peeling off from the surface of a substrate due to the internal compressive stress, as high as 1-2 GPa, generated in the film resulted in the limitation of the film thickness as thin as 1-3 µmm. The purpose of this study is to establish a technology which can synthesize DLC films thicker than 40 um, for micromachine members, using the RF plasma CVD method. The results showed that the introduction of Si element can reduce the stress to about 0.8 GPa, and the formation of multi-layered structure accompanied with introduction of Si element can reduce it much more to 0.68 GPa i.e., succeeded in reducing the stress as much as 30-60 % compared with that in the film synthesized by conventional techniques. Furthermore, the reduction of the stress realized the formation of freestanding thick DLC film that can be used as the material for micromachine members. Micro cutting and grooving performances of the film, by the usage of laser and Focused Ion Beam techniques, are also shown.
DP-24 Effect of Temperature in Controlling Plasma Etching of Silicon Substrates for the Formation of Monolithic Silicon Nanotips C.H. Hsu (National Taiwan University, Taiwan, R.O.C.); H.C. Lo (National Chiao Tung University, Taiwan, R.O.C.); S Chattopadhyay, K.H. Chen (Academia Sinica, Taiwan, R.O.C.); C.F. Chen (National Chiao Tung University, Taiwan, R.O.C.); L.C. Chen (National Taiwan University, Taiwan, R.O.C.) Formation of well aligned silicon nanotips etched monolithically from a silicon substrate has been demonstrated. The effect of the growth temperature on the morphology of these nanotips has been investigated. The longest nanotips (2.2 µm) were formed at growth temperatures of 250°C and then decreased in length with increasing growth temperature. Above 800°C, the growth of the silicon nanotips were inhibited. This has been attributed to the efficient formation of silicon carbide thin film at higher growth temperatures, instead of discontinuous nanomasks at lower growth temperatures, that prevents etching of the substrate. Another contribution to this inhibited growth of nanotips is the decaying etching rate of the silicon by agents such as atomic H at higher growth temperatures.
DP-25 Modification of Si Nano Emitters by Diamond-clad Process C.L. Tsai, C.F. Chen (National Chiao Tung University, Taiwan, R.O.C.) The potential to achieve high-current devices is one of the most attractive issues of field emitters. In this work, needle-like Si tips with high aspect ratio is achieved by hydrogen plasma. Scanning electron microscopy (SEM) shows the average diameter and height of need-like Si tips are approximately 70 and 350 nm, respectively. To improve the field emission property of pure Si tips, the diamond-like carbon nanoparticles are further deposited on the top of the Si tips. Experimental results present that the diamond-like carbon-clad process improves the stability as well as the conductivity. Transmission electron microscopy (TEM) and Raman spectroscopy are used to observe their nanostructures and quality. Besides, the Auger electron spectrum also detects the partial growth of silicon carbide during modification process. The more detail will be presented in the conference.
DP-27 The Investigation of Micro-Mechanisms on DLC Coating Prepared By Filtered Cathodic Arc Technique M.-S. Leu, L.-G. Chao, N. Yang, W.-T. Hsiao (Industrial Technology Research Institute, Taiwan, R.O.C.) An investigation of micro-mechanism of diamond-like carbon coating (DLC) thin films prepared by filtered cathodic arc deposition technique is reported. It has been observed that the amplitude of magnetic field on the filter device will affect the adhesion property of the DLC coating. As the magnetic field was increased to more than 100 Gauss, the coating deposited on the silicon and stainless steel substrates were easily to peel automatically as the specimen was taken from vacuum to atmosphere state. Besides, as the different interlayer made by Cr and Ti elements will get different mechanisms of microstructure. The adhesion property on the DLC coating of Cr interlayer was better than the DLC coating of Ti interlayer. But the DLC coating of Ti interlayer has a very excellent micro-hardness of about 45 GPa, which was measured by nano-indenter. The sp³ bonds fraction in these DLC coatings were examined close to about only 60 % by Raman spectroscopy and X-ray photoelectron spectroscopy. However, such a low sp³ fraction can be correlated to the well distributed nano-scale particles of graphite on the DLC coating.
DP-28 The Effect of H and Si Incorporation on the Tribological Property of DLC Coatings in Water Environment S. Ohmoto, K. Yamamoto (Kobe Steel Ltd., Japan) A series of DLC coatings which contain H and Si as dopant, were deposited by UBMS (unbalanced magnetron sputtering) and tribological behavior under water lubrication was investigated. Mechanical and structural properties of doped DLC coatings were investigated against concentration of doped elements and deposition conditions such as substrate bias. Concerning the structural analysis, Raman spectroscopy, XPS and AES-EELS were used to determine chemical bondings and short-range cluster structure. Friction tests were conducted using a ball-on-disk tribometer with a normal load 2, 5 N, sliding velocity 0.5m/s.Both disks and balls were AISI 630 and only disks were DLC coated. In case of H added DLC coatings, the specific wear rate was increased as the hardness of DLC coatings and no observable correlation was found between wear rate and H content. In case of Si containing DLC coatings, wear rate was smaller compared to the H added DLC coatings with comparable hardness. The effect of Si addition on tribological property will be reported in terms of structural and change in chemical nature of DLC coatings.
DP-29 Structure and Biocompatibility of Phosphorus Doped Diamond-like Carbon Films Synthesized by Plasma Immersion Ion Implantation Deposition S.C.H. Kwok, J. Wang, P.K. Chu (City University of Hong Kong) There is increasing interest in developing novel coatings to improve the blood compatibility of cardiovascular implants such as artificial heart valves and bones. In this paper, the structure and biocompatibility of phosphorus-doped diamond-like carbon (DLC) films prepared by plasma immersion ion implantation and deposition (PIII-D) are presented. The films structure and physicochemical properties are evaluated using different chemical and biololgical techniques. Microstructures manifesting as dots are visible under optical microscopy while atomic force micrographs disclose that these round and flat islands are distributed evenly on the film surface. AES and XPS show that they are composed of C, P and O while only C and O can be found in the areas away from the islands. ATR-FTIR spectroscopy indicates the presence of many PO_x and CP_xO_x species. The P-doped DLC film exhibits excellent wettability (16.9o water contact angle) and the Hall effects measurement reveals successful conversion from p (undoped) to n-type (after phosphorus incorporation). To evaluate the blood compatibility, in vitro platelet adhesion and coagulation factor experiments are conducted. The amount of adherent platelets and platelet activation are reduced on the P-doped DLC film, and it is believed that the superior hemocompatibiltiy is due to the improved interfacial tensions and perhaps the change in the semiconducting properties.
DP-30 Electrodes with Carbon Based Nano-materials for Proton Exchange Membrane Fuel Cell C.C. Chen, C.F. Chen (National Chiao Tung University, Taiwan, R.O.C.) The utility of platinum is a main limitation for the development of proton exchange membrane fuel cells. On the basis of cost reduction, variety of carbon based nano-materials such as carbon nanotubes and carbon nanowalls were fabricated on the graphite paper utilizing bias assisted microwave plasma enhanced chemical vapor deposition. The depositions of catalysts for growth of carbon based nano-materials were carried out by electroless plating and e-beam evaporation technologies. During the growth process, the electrical field dominated the formation of nanotubes or nanowalls. The carbon nanowalls can be produced by switching bias. The characteristics of morphologies and structures were achieved by means of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. These materials revealed extremely high surface area from the BET test. With comparison of traditional carbon black, these materials are more suitable as the electrodes for proton exchange membrane fuel cell. Also, the effects of different platinum deposition methods were discussed in detail. High resolution transmission electron microscopy shown the diameters of platinum particles were only several nanometers. BET measurement appealed the high utility of platinum catalysts. Therefore, cost reduction can be realized by using carbon based nano-materials as the platinum supports.
DP-31 RF Plasma Deposition of Thin Si_xGe_yC_z:H Films using a Combination of Organometallic Source Materials C. Rapiejko, M. Strojek, H. Szymanowski, L. Klimek, M. Gazicki-Lipman (Technical University of Lodz, Poland) Since its very beginning, elements of the IV group of periodic table, with particular presence of carbon and silicon, have been accompanying a fast development of PECVD techniques, taking place in the last two decades. As a result, deposition technologies of such materials as a-Si:H, a-C:H orμ-C:H (DLC) have been successfully established. What followed, was an ever growing interest in binary systems of the A_x(IV)B_y(IV):H kind. One possible way to deposit such systems comprises a use of either organosilicon compounds¹(to deposit Si_xC_y:H films) or organogermanium connections²(to deposit Ge_xC_y:H materials), as source substances. The present paper reports on an RF plasma deposition of a Si_xGe_yC_z:H trinary system, using a combination of organosilicon and organogermanium compounds. Thin Si/Ge/C films have been fabricated in a small volume (ca. 2dm³) parallel plate RF plasma reactor using, as a source material, a combination of tetramethylsilane (TMS) and tetramethylgermanium (TMG) vapours carried by argon. SEM investigations reveal a continuous pinhole-free character of the coatings and their uniform thickness. Elemental composition of the films has been studied using EDX analysis. The results of the analysis show that the elemental composition of the films can be controlled by the TMG/TMS ratio in the initial mixture. Ellipsometric measurements show good homogeneity of these materials. Chemical bonding in the films has been studied using FTIR technique. Bandgap calculations have been carried out using ellipsometric data and applying both the Tauc law and the Moss' approach. ¹ A.M. Wrobel and M.R. Wertheimer, Chapter 3 in: R. d'Agostino (Ed.) "Plasma Deposition, Treatment and Etching of Polymers", Academic Press, Boston 1982² M. Gazicki, Chapter 2 in: S. Mitura (Ed.) "Nanotechnology in Materials Science", Elsevier, Amsterdam 2000.
DP-32 Electrical Breakdown Studies of 90nm-Node Copper Dual Damascene Technology with Various Etching Stop Layer Materials J.H. Lin (Taiwan Semiconductor Manufacturing Company, Taiwan); Y.L.. Cheng (National Chiao-Tung University, Taiwan, R.O.C.); H.C. Chen, J.Y. Cheng, C.M. Wu (Taiwan Semiconductor Manufacturing Company, Taiwan, R.O.C.) Silicon carbides and nitrides have been widely used in the copper dual damascene process as a diffusion barrier and etching stop layer. In this study, the electrical breakdown behaviors of most popularly used silicon carbides and nitrides films, such as SiC, SiCN, SiN-A(A-condition) and SiN-B(B-condition), were investigated with capacitance-voltage(C-V), current-voltage(I-V) and time-dependent-dielectric-breakdown(TDDB) measurement under various voltage bias and temperature conditions. A typical patterned Cu/LK dual damascene structure with silicon carbide or nitride barrier layer was prepared for the breakdown measurement. The correlations of the electrical breakdown behaviors and the physical stress of dual damascene stacks are also discussed in this paper. The failure mechanism analysis was carried out with HRTEM/EDS. The breakdown resistance was found to be closely related to the properties of the barrier films.
DP-33 Dielectric Properties of AlN_x Thin Films Prepared by RF Magnetron Sputtering of Al using a N₂/Ar Sputtering Gas Mixture R.D. Gould (Keele University, United Kingdom); S.A.. Awan (Peshawar University, Pakistan) Aluminium nitride is a low conductivity material having applications as a dielectric and passivation layer. Normally this material is prepared using chemical vapour deposition or molecular beam epitaxy, but following earlier work in which it was shown that silicon nitride may be successfully prepared by RF magnetron sputtering, we have investigated the electrical ptoperties of aluminium nitride prepared by this technique. Al-AlN_x-Al sandwich structures were prepared using a pure Al target with a sputtering gas mixture of N₂/Ar in the ratio 3: 7 (partial pressure 0.40 Pa nitrogen and 0.93 Pa argon) with an RF discharge power of 180 W. Measurements indicated that the relative permittivity was about 9.1 and that the capacitance was independent of applied DC voltage, indicating that Schottky barriers were absent.The AC conductivity σ was observed to follow an expression σ = Aω^s, where A is a constant, ω is the angular frequency and s is an index. Values of s were found to be in the range 0.62-1.31, increasing with increasing frequency in the range 100 Hz-20 kHz and decreasing with increasing temperature in the range 161-373 K. This type of behaviour was consistent with a carrier hopping process having a density of localised states value N ~ 7 x 10²⁴ m^-3. Low temperature activation energies were in the range 0.001-0.008 eV, again indicating the presence of a carrier hopping process. The capacitance showed a decrease with increasing frequency and an increase with increasing temperature, tending towards a constant value at higher frequencies and lower temperatures. Measurements of loss tangent as functions of frequency and temperature showed a minimum which appeared to shift to higher frequencies with increasing temperature. These measurements concur with the model of Goswami and Goswami for samples with ohmic contacts, and are representative of results obtained on other insulating films, including nitrides.
DP-34 Obtentionof Dielectric Films with Low Dielectric Constant using Fluorine S.C. Trippe, R.D. Mansano (Universidade de Sao Paulo, Brazil) The hydrogenated amorphous carbon film (a-C:H) is a material that has as a principal characteristic a low dielectric constant (~1,7) smaller then SiO₂ (~3,7), which is the main material used in technological applications. The main advantage in use of a-C:H is the possibility to obtain small devices without the influence of parasitary capacitance present in the microelectronic devices which difficult the ultra very large integration (sub-half micrometer technology). The films are widely used with passivation layer and used in packaging of devices, because this film has a high thermal condutivity. The purpose of this paper is to present a study of the effect that the addition of fluorine causes in the above mentioned properties of a-C:H films. These films were produced by a reactive RF magnetron sputtering system from a target of pure carbon in a stable graphite allotropic form of nominal purity of 99,9999 %. The a-C:H films were deposited on Si [100] substrates. The fluorine was obtained with CF₄ addition in the plasma process. The concentration of CF₄ added to the plasma of H₂ was varied from 0 to 70 % and the concentration of CF₄ added to the plasma of CH₄ was varied from 0 to 90 %. The parameters which were used during all of the deposition processes are a power of RF 150 W at 13,6 MHz and a pressure of 8 mTorr. The resulting films were characterized, by Atomic Force Microscopy (AFM), by Fourier Transformed Infrared Spectroscopy (FTIR), by Rutherford Backscattering Espectroscopy (RBS). We performed measurements of electrical characteristic curves of capacitance and current as a function of the applied tension (C x V and I x V) to information about dielectric constant and material resistivity.
DP-36 Adhesion Strength of Multi-layered Diamond Films on WC-Co Alloy Substrate S. Takeuchi, M. Kojima, M. Murakawa (Nippon Institute of Technology, Japan) When diamond is used as a wear-resistant material for tools, its unique wear resistance cannot be fully exploited due to the possibility of brittle fracture. In general, diamond films synthesized by the vapor phase method are polycrystalline exhibiting columnar crystal growth. In the polycrystalline structure, once cracks occur on the surface of the film, they tend to propagate through the columnar particles, leading to a decrease in toughness. The authors succeeded in synthesis of a multi-layered diamond films by repeating bias enhanced hot filament method. The multi-layered films was superior in surface roughness, and indicate the bending strength of the film is approximately 30% higher than that of a conventionally produced diamond film. In this study, we synthesized multi-layered diamond film by hot filament method using a W-Co alloy substrate, and evaluated the adhesion strength for various cutting tools.
DP-37 Low-temperature Growth Nano-crystalline Diamond using Low-density Plasma C.T. Hsieh, J.M. Ting (National Cheng Kung University, Taiwan, R.O.C.) Nano-crystalline diamond thin film has received much attention due to the excellent properties it provides. The growth of nano-crystalline diamond thin film is typically accomplished using microwave plasma enhanced chemical vapor deposition (CVD) techniques, hot filament assisted CVD techniques, and ion beam processes. In this paper we report the use of a low-temperature, low-density plasma to grow nanocrystalline diamond thin films. The low-density plasma was generated by an rf source under a pressure that varied from 0.5 torr to 3 torr. The hydrocarbon used was CH₄, which was balanced by H₂ and/or NH₃. The ratio of hydrocarbon and balancing gas was varied from 1/20 to 1/1. The substrate was either not heated or heated to 200 or 400. The substrates used include silicon and glass and were not subjected to any polished prior to the growth. The resulting diamond films were found to consist of nano-crystalline diamond phase whose percentage in the films depends on the growth condition. The diamond films were characterized for structure using micro-Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), and low-angle x-ray diffractometry. The diamond films were also examined for optical transmittance from visible light to UV. The results were then used to determine the value of optical band gap. Atomic force microscopy (AFM) was used to determine the surface roughness.

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