Papers

ICMCTF2003 Session DP: Symposium D Poster Session

Monday, April 28, 2003 5:00 PM in Room Town & Country

Monday Afternoon

Time Period MoP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2003 Schedule

DP-1 Effect of Silicon Doping on the Mechanical, Optical and Structural Properties of Carbon Nitride Thin Films D. Sarangi, R. Sanjines, A. Karimi (Swiss Federal Institute of Technology (EPFL), Switzerland) Carbon nitride thin films have taken much attention due to their predicted extreme hardness values. We, in the present investigations synthesize the CN_x thin films by microwave assisted hot-filament plasma enhanced chemical vapor deposition (PE-CVD) technique using acetylene C₂H₂), ammonia NH₃ and hydrogen H₂) as feedstock gases at about 650°C. The films are doped with Si by using silane SiH₄) gas along with other gases. Nano-indentation, FTIR, RBS, techniques were employed to characterize the deposited Si doped CN_x films. Nano-indentation reveals that the films are very hard. Typical hardness of these films is found to be about 20-24 GPa. The hardness of the films is influenced by the Si doping percentage. FTIR analysis indicates that Si-H, N-H, Si-C, Si-N, C-N and C N triple bonds are present in the Si doped CN_x films. The shift of bands with SiH₄ partial pressure changes also been investigated. RBS measurement reveals that a high amount of nitrogen is incorporated into the film. The typical value of the nitrogen is about 45 at %. The surface morphology and topography of the deposited films also been characterized by SEM and AFM. The influence of substrate bias and the microwave power are studied carefully.
DP-2 Characterization of Ternary Boron Carbon Nitride Films Synthesized by r.f. Magnetron Sputtering D.-H. Kim, D.-G. Kim, U.-H. Nam, E. Byon, J.-K. Kim (Korea Institute of Machinery and Materials, South Korea) Boron carbon nitride (BCN) films are of considerable research interest because of their potential technological applications, in particular, as hard coatings, optical protective layers, and electronic applications because of the structural similarities between BN (cubic boron nitride (c-BN), hexagonal boron nitride (h-BN)) and carbon (diamond, graphite). In this work, we prepared ternary boron carbon nitride (BCxNy) films on silicon wafers by r.f. magnetron sputtering of boron nitride (BN) and graphite targets. The BCN films with different carbon contents were obtained by varying the graphite target power. With increasing of the graphite target power, Fourier transform infrared spectroscopy showed that the structure of the BCxNy films was changed from the cubic BCN to the hexagonal BCN. The composition and bonding characteristics of the films were examined by X-ray photoelectron spectroscopy (XPS). And the possibility of the carbon segregation was studied by Raman spectroscopy when the graphite target power was increased. From this work, we have found out the possibility that the structure of the BCN films was controlled from the cubic to the hexagonal and the properties of the films were also changed according as their structures.
DP-3 Corrosion Behavior of Boron Carbon Nitride Films Grown by Magnetron Sputtering E. Byon (Korea Institute of Machinery and Materials, Korea); M. Son (National Institute of Advanced Industrial Science and Technology, Japan); K. Sugimoto (Tohoku University, Japan) Boron-Carbon-Nitrogen (B-C-N) system is an attractive ternary material since it has not only an extremely high hardness but also a number of other prominent characteristics such as chemical inertness, elevated melting point, and low thermal expansion. In this paper, the corrosion behavior of B-C-N thin films in aqueous solution was investigated. B-C-N films with different composition were deposited on a platinum plate by magnetron sputtering in the thickness range of 150-280nm. In order to understand effect of pH of solutions, BC_2.4N samples were immerged in 1M HCl, 1M NaCl, and 1M NaOH solution at 298K respectively. BCN samples with different carbon content were exposed at 1M NaOH solutions to investigate effect of chemical composition on corrosion resistance. Corrosion rate of samples were measured by ellipsometry. From results, optical constant of B_1.0C_2.4N_1.0 films was found to be N₂=2.110-0.295i. The corrosion rates of B_1.0C_2.4N_1.0 films were NaOH>NaCl>HCl in sequence. With increasing carbon content in B-C-N films, the corrosion resistance of B-C-N films is enhanced. The lowest corrosion rate was obtained for B_1.0C_4.4N_1.0 films.
DP-4 Mechanical and Optical Properties of Hard SiCN Coatings Prepared by Low Temperature PECVD P. Jedrzejowski (École Polytechique de Montréal, Canada); J. Cizek (University of West Bohemia, Czech Republic); A. Amassian, J.E. Klemberg-Sapieha, L. Martinu (École Polytechique de Montréal, Canada) Novel amorphous SiCN coatings are becoming very attractive because of their mechanical, optical and electronic properties. In the present work, SiCN films were fabricated by PECVD from SiH₄/CH₄/N₂/Ar gas mixtures at an intermediate substrate temperature of 400°C. Mechanical characteristics such as nanohardness, Young's modulus, friction coefficient and stress were evaluated, respectively, by depth-sensing indentation, microscratch and curvature methods. Their behavior is correlated with the film microstructure and composition determined by SEM, ERD-TOF, XPS, AFM and broad range spectroscopic ellipsometry. Films deposited under optimized conditions exhibited a hardness of >30 GPa, Young's modulus of >190 GPa, elastic rebound of nearly 90%, and a compressive stress of about 1 GPa. A very low friction coefficient of about 0.05 and a low surface roughness of about 1 nm were found to be accompanied by a refractive index ranging from 1.75 to 2.1 (at 550 nm) and an extinction coefficient between 110^-4 and 3.510^-2. Film properties are correlated with the microstructure.
DP-5 Growth and Cathodoluminescence Properties of Oriented Silicon Carbon Nitride Films Ching-Hsing Shen (National Taiwan University, Taiwan, ROC); Ming-Shien Hu (Academia Sinica, Taiwan, ROC); Lu-Sheng Hong (National Taiwan University of Science and Technology, Taiwan, ROC); K.-H. Chen (Academia Sinica, Taiwan, ROC); L.-C. Chen (National Taiwan University, Taiwan, ROC) Ternary SiCN phases are attractive because of their potential application for high-speed electronics as well as blue and UV optoelectronic devices. In this report, we demonstrate oriented growth of SiCN films by microwave plasma enhanced chemical vapor deposition (MPCVD) with N₂, H₂, CH₄, and SiH₄ as the reaction source gases. Polished Si (100) wafers coated with SiC layer by thermal chemical vapor deposition were used as substrates. We found that the addition of argon gas during the microwave CVD process would promote oriented growth of SiCN crystals. Structure and morphologies of SiCN crystals were studied by field emission scanning electron microscopy and high resolution transmission electron microscopy. Composition and bonding were determined by energy dispersive spectroscopy and X-ray photoelectron spectroscopy analyses. In addition, high spatial resolution cathodoluminescence was performed to study luminescence property.
DP-6 Growth and Field Emission of Carbon Nanotubes on Gated Structured Device C.-F. Chen, C.-L. Tsai (National Chiao Tung University, Taiwan, ROC) Carbon nanotubes have attracted much attention of many scientists worldwide. The nanometer-size diameter, structural integrity, high electrical conductivity and chemical stability make them very good electron emitters. To date numerous works have been published on carbon nanotubes as emitters in a diode device. However, carbon nanotubes directly grown on the gated structured device is the trend for commercial use. In this study, selective area deposition of high-density carbon nanotubes grown on the 4 mm gated structured metal-insulator semiconductor (MIS) device is achieved by using a Pt layer as nucleation inhibitor. Besides, vertically well-aligned carbon nanotubes were synthesized on catalyst-deposited Si substrate in the bias-assisted microwave plasma chemical vapor deposition. Moreover, we use scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to observe their morphology and microstructures; Raman spectroscopy to analyze the quality of carbon nanotubes and I-V measuring system to obtain their field emission characterization. The more detail will be presented in the conference.
DP-7 Behavior of Carbon Thin Films at High Pressure and Temperature in Diamond Anvil Cell. L.K. Shvedov, N.V. Novikov, O.G. Lysenko (Institute for Superhard Materials, Ukraine) The diamond anvil cell (DAC) is widely used 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 (PT) and relaxation of intrinsic stresses in carbon materials. The X-ray and acoustic emission technique and apparatus were used for analysis of thin films under high pressure and temperature. The carbon films were deposited from RF-discharge plasma (operating frequency being 13.56 MHz) in a capacity type reactor. Behavior of carbon thin films on different substrates at pressure up to 30 GPa and different levels of temperature have been studied. Experiments have shown decreasing in intrinsic stresses of thin films and changing in their phase structure after high-pressure and temperature action.
DP-8 Synthesis of Thick DLC Film for the Micromachine Members S. Takeuchi, A. Tanji, H. Miyazawa, 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 um. 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-9 Self Selective Vertical Alignment of Carbon Nanotubes S.-H. Kim (Silla University, South Korea); T.-G. Kim (Miryang National University, South Korea) We deposited carbon nanotubes by using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system. The vertical alignment of carbon nanotubes could be obtained by the application of the negative bias voltage onto the substrate during the reaction. We observed the selective formation of carbon nanotubes onto the substrate as a function of the characteristics of the catalyst. Finally, the self selective vertical alignment of carbon nanotubes could be achieved by selecting the optimal characteristics of the catalyst under the higher negative bias voltage ( > -300 V ) condition. Detailed process to obtain the self selective vertical alignment of carbon nanotubes was presented. The characteristics of the carbon nanotubes were investigated as a function of the characteristics of the catalyst. Based on these results, the cause for the achievement of self selective vertical alignment of carbon nanotubes is discussed.
DP-10 Effect of Cycling Oxygen Flow Rate on the Enhancement of Diamond Nucleation Density S.-H. Kim (Silla University, South Korea); T.-G. Kim (Miryang National University, South Korea); J.H. Yang (Changwon Polytechnic College, South Korea) We deposited diamond films by using a microwave-plasma-enhanced chemical vapor deposition (MPECVD) system. To enhance the diamond nucleation density, we apply cyclic on/off modulation of oxygen gas flow during the initial deposition stage as a function of the reaction time. Detailed process to enhance the diamond nucleation density by applying cyclic on/off modulation of oxygen gas flow was presented. Surface morphologies and diamond qualities of the films were investigated as a function of oxygen gas flow on/off time ratio. The diamond nucleation densities would be much more enhanced under the condition of the lower oxygen gas flow on/off time ratio. The enhancement of the diamond qualities by the cyclic process was noticeable under the condition of the higher oxygen gas flow on/off time ratio. Based on these results, we discussed the cause for the enhancement of the diamond nucleation densities and the diamond qualities as a function of oxygen gas flow on/off time ratio.
DP-11 Multi-wall Nano-onion and Nanotube Structures Produced by Arc Discharges in Water J.J. Hu, J.E. Bultman, J.S. Zabinski (Air Force Research Laboratory, WPAFB) Nano-structured particles such as inorganic fullerene-like (IF) WS₂ and MoS₂ have been studied for tribological applications in the past few years. The advantages of IF nanoparticles include (1) closed, oxidation resistant structures, (2) ultra-low friction, and (3) wide environmental operating range. However, the cost of making nano materials is relatively high because of the use of vacuum chambers or purge-gas handling systems in their fabrication. Simple arc-methods utilizing water or liquid nitrogen mediums permit continuous synthesis of nanoparticles at relatively low-cost and they are environmentally benign. Other authors have reported growth of carbon nano-onions and nanotubes in water and liquid nitrogen. In this study, an easily controlled arc discharge system was built and used to grow some familiar as well as new structures. Multi-wall nano-onions and nanotubes were formed simultaneously during arc discharging of graphite rods in water. High-resolution transmission electron micrographs also revealed the existences of some hollow and polyhedral carbon nanoscale particles. The tribological properties of the nanostructures will be presented and the discharge conditions leading to the different carbon structures will be discussed.
DP-12 Photoluminescence of Carbon Films Produced by Polyethylene-Glycol Pyrolisis V. Baranauskas, M. Fontana, H.J. Ceragioli, A.C. Peterlevitz (Faculdade de Engenharia Elétrica e Computação - UNICAMP, Brazil) Luminescent carbon films have been prepared by dipping the substrates (Si or quartz) in polyethylene-glycol and subjecting the coating to pyrolysis at different temperatures under an inert gas atmosphere. The carbon coatings obtained using this method showed good adherence and uniform thickness. Films prepared in the 473-673 K range have been characterized by micro-luminescence, micro-Raman spectroscopy. Morphological data obtained using scanning electron microscopy (SEM) and atomic force microscopy (AFM) are also presented.
DP-13 Influence of Metal Plasma Ion Implantation on Selected-area Nucleation and Growth of Carbon Nanotubes Chi-Lung Chang, D.-Y. Wang (Ming-Dao University, Taiwan, ROC) Clustered and directionally grown carbon nanotube (CNT) has shown great potential in microfabrication of catalyst carriers and nanodevices. In this study, metallic catalysts such as Fe, Ni, Co, and Cr were implanted onto the near surface of silicon substrates before being subjected into CVD plasma for CNT growth. The influence of the medium-energy (30-50 KeV) metal plasma ion implantation (MPII) on the selected-area nucleation and growth of CNT clusters were investigated. The ion energy and dose of each metallic catalyst comprise the major parameters for effective and durable growth of CNT clusters. Scanning probe microscopy (SPM), transmission electron microscopy (TEM), Auger electron spectroscopy, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction (XRD) techniques were employed to study the microstructure and growth mechanism of the modified interface. Results indicated that an effective MPII pre-treatment created a favorable condition for nucleation and growth of selected-area CNT clusters. Keywords: carbon nanotubes, metal plasma ion implantation, interface, catalyst.
DP-14 Electron-emission from Nano- and Micro-crystalline Diamond Films: the Effects of Nitrogen and Oxygen Additives S.H. Seo, T.H. Lee, C.K. Park, J.S. Park (Hanyang University, South Korea) Recently, CVD diamond films have received great attention as electron emitters for vacuum microelectronic devices since diamonds exhibit a negative electron affinity (NEA) surface that allows diamond surface to emit electrons under a relatively low electric field. Although the CVD diamond films may exhibit the NEA nature, the undoped films inherently possess a significantly small concentration of electrons in the conduction band due to wide band gap energy (~ 5.5 eV), which may act as a barrier that prevents the electron-emission. For this reason, n-type doping of diamonds with several donor atoms like lithium, phosphorus, and nitrogen is considered to be very essential for enhancing the emission capability of diamond films. In addition, it is known that the electron-emission from diamond may depend on the crystal structure that includes micro- and nano-crystalline. However, a successful method for the n-type doping has not been introduced in literature and furthermore, an exact mechanism responsible for the electron-emission is not clearly elucidated. In this research, we investigate the electron-emission properties of nanoand micro-crystalline diamond films, which are grown using a microwave-plasma CVD method, by placing special emphasis on the effects of nitrogen and oxygen additives. For all the grown films, Raman spectra, XRD patterns, and field-emission SEM morphologies are characterized in terms of growth conditions and the electron-emission is measured using a parallel plate configuration at a pressure below 2x10^-7Torr. Nitrogen-incorporated diamond films are also prepared by injecting an additive N₂gas and varying the N₂/(CH₄+H₂) ratio from 0.5 to 2.0 %, which is performed with or without adding an O₂ gas. By increasing the CH₄/H₂ratio, the emission current density significantly increases from a few pA/cm²to 50µmA/cm²at 15 V/µm. This may be attributed to the phase transition of grown films from micro- to nano-crystalline. For the grown microcrystalline films, it is to be noted that by adding the O₂ gas, the emission current density remarkably increases, while it slightly changes by increasing the N₂/(CH₄+H₂) ratio. Cathodoluminescence (CL) studies on the nitrogen-incorporated films clearly show that the nitrogen-related CL emission becomes stronger by adding the oxygen. This may indicate that the oxygen plays an important role in the incorporation of N atoms into the grown diamond films. Similar experiments are also performed with nano-crystalline diamond films and finally the long-term stability for the electron-emission is discussed.
DP-15 Stress Reduction of cBN Films by Addition of H₂ During Sputter Deposition H.S. Kim, Y.-J. Baik (Korea Institute of Science and Technology, South Korea) During the past few years, many authors have reported the hydrogen effect in the cBN deposition including the computational calculations. Regardless of many previous results on the investigations of chemical reaction, key questions of stress reduction and cBN microstructure variation have not been studied in a systematic way. In this study, we investigated the role of hydrogen ion during the cBN growth focusing on the stress reduction. BN films were deposited on (100) Si wafer by using radio-frequency (RF) unbalanced magnetron sputtering source. Hexagonal boron nitride disk (99.9% in purity) was used as a sputter target. The BN films were deposited at 400 W of target radio-frequency (13.56 MHz) electric power and with various substrate bias voltages (200 kHz high-frequency). The chamber was evacuated to a pressure less than 1.0X10^-5 Torr and then filled with argon - 10% nitrogen mixed gas up to 1.3 mTorr. The hydrogen gas was added from 0.25 sccm to 2 sccm during the cBN film growth. During the precleaning and deposition process, a substrate holder (100 mm in diameter) was not heated additionally. The residual compressive stresses of cBN films were reduced by addition of hydrogen during cBN growth. The decrease of Ar concentration at the aligned tBN interface may reduce the residual compressive stress considerably. It is confirmed that Ar incorporation in the tBN interface layer may be interrupted by the adsorption of hydrogen and the nucleation of cBN phase may be possible without high compressive stress. The adhesion of cBN films is also improved by hydrogen addition.
DP-16 Interaction of Oxygen with a-C and a-C:H Films V. Kulykovskyy (Institute for Problems of Materials Science, NASU, Czech Republic); V. Vorlicek, P. Bohac, J. Zemek (Institute of Physics AS CR, Czech Republic); A. Kurdyumov (Institute for Problems of Materials Science, NASU, Ukraine); L. Jastrabik (Institute of Physics, AS CR, Czech Republic) New type of amorphous graphite-like CO_x films was obtained by two ways: (i) magnetron sputtering of graphite target in the gas mixture Ar + O₂; (ii) air annealing at 250 - 300°C of a-C and a-C:H films deposited by magnetron sputtering in Ar or gas mixture Ar + CH₄. These films contain at most 18 - 22 % of atomic oxygen depending on the way of their preparation. They remain stable in air and vacuum up to 300 °C. The transition from graphite-like a-C to a-CO_0.2 is accompanied by sharp increase of electrical resistivity and IR transmittance. Two characteristic absorption bands at approximately 1700 and 1605 cm^-1 appear and the G band in Raman spectrum shifts to ~ 1605 cm^-1 in a-C and a-C:H films. After vacuum annealing of a-CO_x films at 750°C G band shifts from ~1605 cm^-1 to ~ 1595 cm^-1 and the oxygen content in these films sharply decreases. The electron diffraction reveals that only the films with the 002 interlayer distance increased with respect to graphite may be saturated with oxygen up to ~ 22 atomic % until they become strongly vaporized.
DP-17 Enhancement of sp³ Bonding Characteristic in Amorphous Carbon (a-C) Films by Chemical Bond Modification with Si-incorporation H.S. Jung, H.H. Park (Yonsei University, South Korea); J.-L. Lee (Pohang University, South Korea) The formation of highly tetrahedral, dense amorphous carbon (ta-C) films has generally been attributed to the deposition by energetic species. This work demonstrates that it is possible to deposit highly sp³ bonded amorphous carbon (a-C) by chemical bond modification and physical ion bombardment. In this work, Si incorporated amorphous carbon (a-C:Si_x) films have been deposited by co-sputtering of graphite and silicon targets. For the physical ion bombardment of deposited a-C:Si_n films, DC Ar ion plating is induced to Si substrate. Structure and properties of these films are controlled by deposition parameters such as sputtering power and substrate bias. From this process, Si/C ratio for these films can be in range of 0-0.9, however the minimum Si/C ratio in this work was 0.04. The bonding configurations have been identified from X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FT-IR) spectroscopy and Raman spectroscopy. Specially, Raman spectroscopy and XPS were used to probe the topographical nature of three- and four-fold coordinated carbon atom bonding and clustering of their distribution. Also, to investigate the thermal stability of this film, film stress and shrinkage after anneal were evaluated at various temperatures up to 500 °C.
DP-18 Fluorinated Carbon Nanotubes Produced Directly in Anodic Alumina Template via Electron Cyclotron Resonance Plasma S.-H. Lai (National Tsing Hua University, Taiwan, ROC); K.P. Huang (National Chiao Tung University, Taiwan, ROC); L.-H. Chan (National Tsing Hua University, Taiwan, ROC); P. Lin (National Chiao Tung University, Taiwan, ROC); Han. C. Shih (National Tsing Hua University, Taiwan, ROC) Unlike the general fluorination, the amorphous fluorinated carbon nanotubes (a-C:F NTs) have been synthesized directly by an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system with a mixture of C₂H₂, CF₄ and Ar as precursors. The a-C:F NTs were produced in anodic alumina membrane template which consisted of a packed array of parallel, straight, uniform channels. The plasma chemistry of the system was analyzed by optical emission spectrometer (OES) to investigate the active chemical species that were involved in the formation of a-C:F NTs. The morphology of aligned a-C: F Nts were observed by SEM and TEM. X-ray photoelectron spectroscopy (XPS) was used to investigate changes in the surface chemical nature of a-C:F NTs. XPS and Fourier transform infrared spectroscopy (FTIR) spectra showed that C-F bonding varied from semi-ionic to covalent with increasing deposition temperature from R.T. to 300°C. With increasing deposition temperature, the ratio of fluorine to carbon (F/C) is increasing which was determined by XPS.
DP-19 Deposition of DLC Films by Mechanically Induced Decomposition of Organic Compounds A. Torosyan (Armenian Academy of Science, Armenia); L. Takacs (University of Maryland Baltimore County); A. Bakhshai (Goucher Collage) Diamond like carbon (DLC) is an amorphous form of carbon with hardness near to the hardness of diamond (i.e. up to about 80 GPa) and remarkably low friction (friction coefficient around 0.1 in air). In addition, DLC is a chemically inert material that makes DLC coatings an attractive candidate for a wide variety of engineering applications. Several techniques have been successfully used for the deposition of DLC film, among them pulsed laser deposition, the pulsed vacuum arc-discharge source process, CVD, etc. Simultaneously, the structural, mechanical and physical properties of DLC coatings are the subjects of intense investigations. In particular, questions concerning the adhesion of DLC films to the substrate and the coating of three-dimensional objects with a DLC layer require further studies. The microstructure of DLC films is an important subject of investigation, because the mechanical and physical properties of the coating depend on the microstructure while the microstructure itself can be controlled by the deposition technique. The present study describes a novel technique for the deposition of DLC films that is based on the in situ mechanically induced decomposition of organic compounds. Several DLC films have been deposited by mechanically induced decomposition of solid (naphthalene) and liquid (toluene) compounds under a variety of conditions. Raman spectroscopy, SEM microscopy, and X-ray diffraction were utilized for the characterization of the obtained layers. The authors expect that DLC films deposited by mechanochemical methods will find trybological applications due to their advantageous microstructure formed under mechanical impact conditions.
DP-20 Carbon Films Synthesized by Atmospheric Plasma CVD H. Kodama, T. Suzuki (Keio University, Japan) Thin films are generally deposited using vacuum technique, but vacuum process costs much for cheap plastic products. There are few reports on atmospheric plasma as papers, but many researchers have paid attention to its importance. At the beginning, this technique has been used for etching in the semiconducting fields. In this study, we designed and set up atmospheric plasma CVD equipment and successfully synthesized carbon films using acetylene gas. The XPS, Raman spectroscopy and cross-sectional TEM techniques were used for analyzing films.
DP-21 Effects of Bias Voltage on Initial Nucleation of CVD Diamond Deposited on Si Substrates I. Kiyoto, H. Kodama, T. Suzuki (Keio University, Japan) It has been recognized that highly oriented-diamond films could be obtained on Si substrates by the bias-enhanced nucleation (BEN) pretreatment. In this study, we measured changes in bias current against time at various bias voltages to investigate the nucleation mechanism of CVD diamond. It was found that a negative bias voltage over 100V was required to obtain high nucleation density, although sufficient BEN treatment times were also necessary. The excess BEN treatment with higher voltage and longer time led to form secondary nucleation, which was obviously detrimental effects to obtain flat epitaxial diamond films. Cross-sectional transmission electron microscopy (TEM) showed that several layers of SiC were epitaxially grown on Si substrate and that diamond nuclei are deposited on SiC. Effects of bias-voltages on the nucleation behavior were studied based on the observation by Raman spectroscopy, X-ray photoelectron spectroscopy and TEM.
DP-22 The Thermal Stability of Microhardness and Internal Stress of the Hard a-C Films with Predominantly sp² Bonds V. Kulykovskyy (Institute for Problems of Materials Science, NASU, Ukraine); V. Vorlicek, P. Bohac (Institute of Physics AS CR, Czech Republic); A. Kurdyumov (Institute for Problems of Materials Science, NASU, Ukraine); A. Deineka, L. Jastabik (Institute of Physics AS CR, Czech Republic) Study of the thermal stability of microhardness (H) and its connection with level of the internal stress in superhard and thick (about 1.5 µm) a-C films formed with predominantly sp² bonds is the main goal of this paper. Microhardness, internal stress and Raman spectra of the hardest film (H ~ 50 GPa) produced by magnetron sputtering have been investigated in dependency on annealing temperature (up to 820°C). The changes of microhardness and internal stress of this film after annealing in vacuum do not correlate to each other. Annealing up to 500°C leads to substantial increase of microhardness and simultaneous decrease of internal stress. It indicates that not only internal stress, but also the special film nanostructure formed in the process of film growth is responsible for the high hardness of this film. The compressive stress do not relax fully even after annealing at 820°C and the microhardness remains enough high (H ~ 40 GPa). The analogous data for thick a-C films with lower hardness (H ~ 20 GPa ; H ~ 10 GPa) are presented for comparison too. It is shown that a release of even relatively small compressive stress of 0.7 GPa leads to 0.7 % increase in the linear film size.
DP-23 Characteristics of Carbon Nanotubes with Hot Filament Plasma Enhanced Chemical Vapor Deposition Method K.-H. Jung, J.-H. Boo, Y.-J. Kim, B. Hong (Sungkyunkwan University, South Korea) Carbon nanotubes were prepared by HFPECVD (hot filament plasma-enhanced chemical vapor deposition) system with the various growth conditions which include angles between substrate and anode. The ammonia (NH₃) and acetylene (C₂H₂) gas were used for a dilution and a carbon precursor for the growth of the carbon nanotubes, respectively. The pretreated catalyst layer was investigated with AFM, which shows that the micron-size grains were formed. Also, the films were characterized using SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) with their growth conditions. Raman spectroscopy of nanotubes showed that G-band and D-band peak around 1370 cm^-1 and 1590 cm^-1. The angle between substrate and anode affected the growing direction of carbon nanotube.
DP-24 Analysis of Structures and Compositions in Nitrogen Doped Multiwall Carbon Nanotubes L.-H. Chan, K.-H. Hong, D.-Q. Xiao (National Tsing Hua University, Taiwan, ROC); T.-C. Lin (National Chung Hsing University, Taiwan, ROC); S.-H. Lai, Han. C. Shih (National Tsing Hua University, Taiwan, ROC) Multiwall carbon nanotubes (MWCNTs) doped by nitrogen atoms were synthesized by exposing carbon nanotubes under the atmosphere of nitrogen plasma, using a 3.1 kW microwave input power. The nanostructures were investigated by high-resolution image and selected area diffraction pattern of transmission electron microscopy. Incorporation of nitrogen atoms into carbon nanotubes would distort the original parallel graphene layers, introduce pentagon defects into the structures and increase the local curvatures of graphene layers. Even some fullerene-like structures were formed in the structure. Raman spectrums also showed the more disturbed G-band signals in nitrogen doped MWCNTs. X-ray photoelectron spectroscopy and Fourier transform infrared spectrum in grazing angle method were assisted to track the atomic signals and bonding configurations. It was found that there were no triple bonds of nitride bonding forming in these structures. In addition, the results of electron energy loss spectrum showed that sp² contents of carbon would increase when nitrogen is doped into MWCNTs.
DP-25 Hydrogen and Oxygen-related Defects in Combustion-deposited Diamond Films Subjected to Different Heating Process L.M. Apatiga, R. Velazquez, V.M. Castano (Universidad Nacional Autonoma de Mexico) Hydrogen and oxygen-related defects in polycrystalline diamond films were studied by FTIR sepctroscopy. The films were deposited by the combustion flame technique at 800°C in open atmosphere using an oxy-acetylene gas mixture. The hydrogen and oxygen-related defects were studied through the FTIR spectral changes followed during different heating process, in the temperature range from 400 to 1000°C. It was found that the hydrogen and oxygen are present on as-deposited diamond films surfaces as a result of the growth process. The C-H and C-O vibrational frequencies came from two contributors, the diamond crystallite surfaces and the diamond grain boundaries, they were assigned according to the type of carbon hybridization and to the type of group. After a heat treatment at 600°C, the weight loss measured through the high temperature thermogravimetry analysis, show an appreciable oxidation that progresses rapidly at 1000°C. The oxidation of diamond was accompained by a redistribution in the FTIR intensities, with some peaks growing and other decreasing.
DP-26 Amorphous Hydrogenated Carbon-nitrogen Alloys Prepared by RF-PECVD EF Motta, I. Pereyra (University of Sáo Paulo, Brazil) Carbon nitride compounds have attracted much interest due to the predicted superior properties of C₃N₄. Thus the accurate determination of material composition, in order to evaluate whether an ideal phase can be obtained is of paramount importance to study the growth of CN_x films. Therefore, the relationships between the deposition, the growth mechanisms, the microstructure and electronic density of states of carbon nitride films prepared by PECVD from hydrocarbons needs to be understood. In this work, films deposited on Si (100) substrates in a 13.56 MHz, RF driven plasma reactor at 150° C using methane, nitrogen and noble gas mixtures are studied. The ration of N₂ to CH₄ was varied from 1 to 50 and noble gases (NG) were added to the mixture, varying the gases flow fraction (NG/ NG⁺ N₂) from 0 to 1. The films are characterized by FTIR spectroscopy, Raman scattering, perfilometry, ellipsometry, and Rutherford Backscattering (RBS). It is shown that increasing nitrogen fraction favors the increase of nitrile groups and that the incorporation of noble gases leads an increasing of the deposition rate and to an increase of the CN bonds and a decrease in the CH bonds.
DP-27 Synthesis and Characterization of Nanostructured Carbon Films on Ni/Cu Surfaces Deposited by Pulsed-DC-PECVD J.G. Céspedes, J.L. Andújar, C. Corbella, M. Vives, G. Viera, E. Bertran (Universitat de Barcelona, Spain) Nowadays, nanostructured carbon films represent a very promising field for many applications related with sensors and membranes. In the current work, it was studied the growth of nanostructured carbon on Ni, Cu and Ni/Cu catalyst metal layers deposited on a pretreated surface. The metallic layers were deposited by RF magnetron sputtering while the nanostructured carbon was grown on them by RF-PECVD and pulsed-DC-PECVD. The growth of nanostructured carbon was studied under several deposition conditions of bias voltage (up to -800V), CH₄:NH₃ ratio (varying from 0.2 to 0.7) and using various catalysts annealing temperature. The resulting films were characterized by high resolutions transmission electron microscopy, HRTEM, selected area electron diffraction, SAED and Raman spectroscopy. The results have been discussed in terms of growth deposition conditions.
DP-28 Growth of Highly-oriented Diamond Films on 6H-SiC (0001) and Si (111) Substrates and the Effect of Carburization T.H. Lee, S.H. Seo (Hanyang University, South Korea); S.M. Kang (Hanseo University, South Korea); J.S. Park (Hanyang University, South Korea) Diamonds have been considered to be a promising semiconductor material for high temperature and high power electronic devices due to its superior properties, such as wide energy gap, high thermal conductivity, and high hole-mobility. To realize the electronic usage of diamonds, it is important to synthesize highly oriented diamond films on non-diamond substrates. The oriented growth of diamonds has mostly been reported on Si (100) substrate. Recently, (111)-oriented diamond films, which are grown on Si (111), 6H-SiC (0001), and Pt (or Ir)/sapphire substrates, have received great attention for electronic applications. In growing oriented diamond films bias-enhanced nucleation (BEN) prior to film growth has generally been carried out to obtain a high density of cubic SiC nuclei which have an orientation preferring the crystal orientation of substrate. In addition, adopting a carburization step to the BEN process is reported to enhance the formation of cubic SiC nuclei. However, there have been no reports on the effect of applying the carburization step to the BEN process in the growth of (111)-oriented diamond film on 6H-SiC (0001) and Si (111) substrates. In this research, we present experimental results regarding to the growth of highly (111)-oriented diamond films on 6H-SiC (0001) and Si (111) substrates by microwave plasma CVD as well as the characterization of carburization effects on the structural property of grown films. The nucleation process is carried out under the condition of working pressure = 40 Torr and microwave power = 900 W. The CH₄/H₂ gas mixing ratios are controlled to be 5 ~ 12 % for the carburization step and 3 % for the BEN process, respectively. The film growth is carried out at a fixed CH₄/H₂ratio of 0.5 % and by varying the microwave power from 700 to 950 W. Raman and XRD results obtained from the grown diamond films show that, by lowering the CH₄/H₂ratio in the carburization step, Raman quality factor increases (up to approximately 90%) and the crystal orientation is transferred from random to (111)-orientation. It is also confirmed from the field-emission SEM measurement that the diamond nucleation density is noticeably increased by adopting the carburization step and highly (111)-oriented diamond films can successfully be grown on 6H-SiC (0001) and Si (111) substrates. Furthermore, the analysis data on lattice structure of grown films are presented employing TEM, RHEED, and EBSD techniques to elucidate the mechanism responsible for the growth of (111)-oriented diamond on 6H-SiC (0001) and Si (111) with carburization.
DP-29 A Study on Mechanical Properties of Diamond-like Carbon Thin Films Prepared by a Microwave Plasma-Enhanced Chemical Vapor Deposition Method W.-S. Choi, I. Chung, B. Hong (Sungkyunkwan University, South Korea) DLC thin films were prepared by microwave plasma-enhanced chemical vapor deposition method on glass and silicon substrates using methane (CH₄) and hydrogen (H₂) gas mixture. The negative DC bias (0 V ~ - 500 V) was applied to investigate the adhesion between the film and the substrate and the film properties. And also another set of films was prepared by doping with silicon. The films were characterized by Raman, AES and FT-IR measurement. The hardness was measured with nanoindentor. And also, the friction coefficients were investigated by atomic force microscope (AFM) in friction force microscope (FFM) mode, which were compared with the pin-on-disc measurement.
DP-30 Characterization of Diamond Coatings on Titanium Substrates V. Baranauskas, H.J. Ceragioli, A.C. Peterlevitz (Universidade Estadual de Campinas - UNICAMP, Brazil) Diamond coatings on pure titanium substrates are of interest for tribological and bio-medical implants, among others. However there are large differences in the thermal expansion coefficients of diamond and titanium, which usually results in poor adherence and residual stress. To minimize this difficulty a two-step deposition process was employed. The first step is designed to accommodate the diamond nuclei to the titanium substrate and the second step is to increase the diamond thickness to its final desired value. A hot-filament. CVD system fed with ethanol highly diluted in hydrogen was employed. The surface and cross-section morphology of the samples, analyzed by scanning electron microscopy (SEM), are discussed in relation with results obtained from micro-Raman spectroscopic analysis.
DP-31 UV Photoresponse of Nano-meter Thin Films In₂O₃ by USP CVD Method Z. Zhou, R. Cui (Shanghai Jiaotong University, PR China) In₂O₃ thin films were prepared by ultrasonic spray pyrolysis CVD (USP-CVD) method. XRD and AFM are used to probe the microstructure and topography of the films The nano-scale size of the grains forming the films could be controlled within the range between 10nm and 100nm by adjusting the deposition temperature and the concentration of the spray solution. The films show a strong UV photoresponse phenomenon. The photoresponse gain reaches 10² with a irradiated 300W mercury light source. A rise time and a fall time of 2 sec. are observed under irradiation of the ultraviolet light. We have proposed a model to explain the high photoresponse gain and long response time of the photoelectron based on coulomb blockage and quantum tunneling in the paper.
DP-32 Root Growth of Multi-well Carbon Nanotubes C.-M. Hsu (Industrial Technology Research Institute, Taiwan, ROC); C.-H. Lin (National Chiao Tung University, Taiwan, ROC); H.-J. Lai (Industrial Technology Research Institute, Taiwan, ROC); C.-T. Kuo (National Chiao Tung University, Taiwan, ROC) In order to develop the effective process to control the nanostructure, orientation and properties of carbon nanotubes (CNTs) and to examine the relationships among the CNTs growth and interfacial reactions, The vertically and horizontally oriented CNTs were successfully synthesized on interlayer-coated Si wafer by MPCVD or ECRCVD with CH₄, H₂ as source gases and Co as catalyst. The SiO₂ interlayer was obtained by wafer oxidation. The Ti interlayer and Co catalyst films were deposited on Si wafer by physical vapor deposition (PVD) method. The interlayer and Co catalyst-coated substrates were then followed by H₂ plasma pretreatment to become the well-distributed nano-particles to act as catalyst for CNTs growth. The deposited nano-structures were characterized by SEM, TEM, HRTEM, XRD, Raman spectroscopy, AES and I-V measurements. The results show that the CNTs deposited by MPCVD are dominated by the vertically-oriented and well-aligned dense CNTs. In general, a single catalyst with an average size of ~ 100 nm could grow many MWCNTs of 10 ~ 15 nm in tube diameter, as so called root-growth model. About effect of interlayer materials, the SiO₂ interlayer prefers to form tip-root growth Co-assisted CNTs, and the Ti interlayer the base-root growth Co-assisted CNTs. This is due to the fact that the 100 nm SiO₂ interlayer can effectively block the chemical bonding of Co with the Si substrate, and both Ti and Co can form silicides to promote the bonding with the substrate and so base-root growth of CNTs, which are in agreement with the results of XRD and XTEM analyses.
DP-33 Significance of Substrate Temperature in Time-modulated CVD N. Ali, V.F. Neto, Y. Kousar, J. Gracio (University of Aveiro, Portugal) The methane pulse cycles performed during the Time Modulated Chemical Vapour Deposition (TMCVD) process had an influence on the substrate temperature. The substrate temperature changed during each high (3%), low (2%) methane pulse cycle from 776 to 802°C, respectively. This study aimed at investigating the effects of substrate temperature, in TMCVD, on key film properties, such as growth rate, morphology and surface roughness. We present new findings obtained from a comparative study, where two types of samples were prepared, sample A and sample B. The latter sample was prepared using TMCVD and the substrate temperature was allowed to fluctuate during the methane pulse cycles. On the contrary, the former sample was prepared under identical conditions employed in producing sample A, but instead the substrate temperature was kept constant throughout the growth process. It was observed that sample B consisted of smaller sized diamond crystallites as compared to sample A. Furthermore, sample B was deposited at a higher growth rate and it displayed a smoother film surface. Several reasons explaining the trends observed relating to substrate temperature and methane flow have been presented.

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