ICMCTF2007 Session DP: Symposium D Poster Session

Thursday, April 26, 2007 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic D Sessions | Time Periods | Topics | ICMCTF2007 Schedule

DP-1 The Effects of Si Interlayer Thickness on the Roughness and Microstructure of the Diamond-Like Carbon Films J.I. Jeong, J.H. Yang, Y.-H. Park (Research Institute of Industrial Science & Technology, Korea) The effect of Si interlayer thickness on the roughness and microstructure of diamond-like carbon (DLC) films has been investigated by employing atomic force microscopy and transmission electron microscopy. The films have been prepared by ion beam excited hydrocarbon plasma with the assistance of pulse bias of 2 kV. The anode voltage of 45 V was chosen to make an appropriate beam current and the benzene was used as a carrier gas. The thickness of prepared DLC film was in the range of around 500 nm. The Si wafer and tungsten carbide were employed as a substrate. The surface of tungsten carbide was polished up to average roughness below 20 nm. Si interlayer was deposited using an un-balanced magnetron sputtering source and the thickness of interlayer was changed from 10 to 50 nm. The change of roughness and microstructure by varying the interlayer thickness will be presented together with the characteristics of DLC films such as friction coefficient and hardness of the films.
DP-2 Substrate Bias Voltage Effect on the Properties of Fluorinated Amorphous Carbon (a-C:F) Films Deposited by Filtered Cathodic Vacuum Arc Plasma System Y.-C. Hsueh, Y.-H. Lin, H.-C. Shih (National Tsing Hua University, Taiwan) Fluorinated amorphous carbon(a-C:F) films were deposited on Si(100) substrates by filtered cathodic vacuum arc plasma system at the working pressure of 0.12Pa under various substrate negative bias voltage in the range from 300 to 750 V. The effect of varying bias voltage on the surface morphology, structure and tribological properties of the DLC films were investigated by means of atomic force microscopy (AFM), Raman spectroscopy, x-ray photoelectron spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), surface energy and contact angle. The results revealed an ultra-small nanostructure on the coating surface at about -750 V bias voltage, the diameters of the a-C:F nano-particles (NPs) films are about 10-20 nm. The transform of the surface morphology of the a-C:F film to the a-C:F NPs film by optimizing the parameters and discussing the growth mechanism. The RMS roughness of a-C:F films were increased from 0.346 to 0.840 nm with increasing the bias voltage. Core-level peak area of N(1s) and C(1s) shift from low to high values also with the increasing bias voltage. The effects of the deposition parameters on the formation of a-C:F films were also investigated in this study. Ref: 1. Yan-Way Li, Yew-Bin Shue, Chia-Fu Chen, Teng-Chien Yu, Jack Jyh-Kau Chang, Diamond Relat Mater 11 (2002) 1227-1233 2. Wei-Jen Hsieh, Chen-Hao Wang, Shih-Hsiang Lai, Jhih-Wei Wong,Han C. Shih, Tzu-Shiang Huang, Carbon 44 (2006) 107-112.
DP-3 Characterization of Hydrogen-Free Diamond-like Carbon Film for Inverted Top Emission Organic Electro-luminescence Application D-Y. Wang, F.-K. Chen (Mingdao University, Taiwan) The applicability of the inverted top emission organic light-emitting diode (TEOLED) with multilayer electrodes depends on an ultra smooth, low-transmittance, insulating substrate overcoat to support the device structure. In this study, the feasibility of the diamond-like carbon (DLC) film as a viable device component for TEOLED was accessed. Owing to its advanced physical and chemical advantages such as high hardness, chemical stability, and wide band-gap optical transparency, the hydrogen-free DLC exhibits promising characteristics as the flexible substrate or TFT component overcoat. Ultra smooth hydrogen-free DLC thin films were synthesized by both PVD and PECVD processes. Raman spectroscopy, FTIR, AFM, and electron microscopy were used to characterize the electronic, morphological, and microstructural properties of DLC. The cathode of TEOLED was made of Bragg reflector (DBR), which was assembled with alternating dielectric thin films, each of a quarter wave-length of the incident light source to enhance the reflectivity efficiency. A commercial grade ITO was adopted as the device anode. The influence of the relative thickness of each intermediate thin film on the brightness and luminance of the TEOLED device will be investigated. The design of the TEOLED will be optimized to reach the emission efficiency of 1-3 cd/A. Keyword: TEOLED, DBR, DLC.
DP-4 Depth Profiling of Fluorine-Doped Diamond-Like Carbon Films (F-DLC): Localized Fluorine in the Top-Most Thin Layer Can Enhance the Non-Thrombogenic Properties of F-DLC T. Hasebe (Tachikwa Hospital, Japan); S. Nagashima (Keio University, Japan); A. Kamijo (The University of Tokyo Hospital, Japan); S. Yohena, T. Yoshimura, T. Ishimaru, Y. Yoshimoto, H. Kodama, A. Hotta (Keio University, Japan); K. Takahashi (University of Tokyo Hospital, Japan); T. Suzuki (Keio University, Japan) Diamond-like carbon (DLC) films attract much attention as anti-thrombogenic coatings for blood-contacting medical devices. It is now well understood that the surface properties of the biomaterial plays the major role in controlling the blood compatibility compared to its bulk properties. Several attempts were reported to improve the blood compatibility of DLC films by doping it with suitable elements such as fluorine, silicon, phosphorus and boron. We have previously reported fluorine-doping in DLC films (F-DLC) showed the excellent non-thrombogenicity in human blood. Although we have demonstrated the key factors for non-thrombogenicity of F-DLC, such as mediated proteins, chemical properties of the surfaces, wettability and surface structures, the mechanism for this advantage has not been fully elucidated. In this present study, we particularly focused on the distribution of fluorine in the F-DLC films, and evaluated the relationship between the distributed fluorine and the non-thrombus properties of F-DLC in the human blood. F-DLC films were prepared on the substrates using radio frequency (RF) plasma enhanced chemical vapor deposition (CVD) method. 50-nm-thick F-DLC film was etched every 10 nm in thickness using Argon plasma in RF-CVD apparatus, and the depth profile analysis of each surface layer was performed by X-ray photoelectron spectroscopy (XPS). Thereafter, each etched layer of F-DLC films was incubated with platelet-rich plasma isolated from human whole blood and evaluated the ratio of platelets-covered area on the sample surfaces. XPS showed the localization of doped fluorine was especially in the several nanometers of top-most thin layer. The number of adhering platelets on F-DLC films was increased in each deeper etched-layer, which corresponded to the decrease of the fluorine content on sample surfaces. Our result indicates that the localized top-most fluorine in the films is one of the key factors to promote non-thrombogenicity of F-DLC films.
DP-6 ¹²⁵Xe Produced from Xenon Atoms Implanted in Amorphous Carbon Thin Films G.A. Viana (Universidade Estadual de Campinas, Brazil); R.G.F. Goncalves, A.S. Leal, L.O. Ladeira, M.V.B. Pinheiro, A. Ferlauto, R.G. Lacerda (Universidade Federal de Minas Gerais, Brazil); P.F. Barbieri, F.C. Marques (Universidade Estadual de Campinas, Brazil) In this work amorphous carbon (a-C) is used as a host matrix for natural xenon atoms for further activation by neutron beam to produce hot ¹²⁵Xe radioisotopes. By electron capture, according to the equation ¹²⁴Xe(n,γ) ¹²⁵Xe(EC) ¹²⁵I, ¹²⁵Xe decays to ¹²⁵I, which is largely used in Brachytherapy seeds. The a-C samples, of about 100 nm, were prepared by a Dual-Ion-Beam-Assisted-Deposition (DIBAD) system on a Si(111) substrate, while natural xenon was implanted during the deposition using a Kaufmann-Like ion gun. A TRIGA-I nuclear reactor was used to irradiate the samples, which were analyzed by gamma spectroscopy in order to identify the radioisotopes activated. The results show that the process is an efficient way to produce ¹²⁵I from the ¹²⁴Xe atoms present in natural xenon implanted in the a-C films. Besides the high mechanical stability of a-C, biocompatibility and the yield of Xe trapping, this process opens a new possibility for the production of low-dose brachytherapy seeds without previous hot materials manipulation.
DP-8 Diamond Synthesis Using high Power Microwave Plasma CVD Y.T. Takami (Chiba Institute of Technology, Japan) Recently, diamond can be synthesized using various CVD methods such as hot filament CVD and microwave plasma CVD. However, the cost for synthesis diamond is so expensive to apply CVD diamond for commercial use. Therefore, large area and high rate growth ere required for low cost production. Investigation was carried out diamond synthesis using high power microwave plasma CVD. Diamond was synthesized using mode translation type microwave plasma CVD apparatus is. Mixture of CH₄-H₂ was used as a reaction gas. CH₄ flow rate was varied from 1.0 to 2.0 SCCM and pressure was varied from 13.3 to 20.0 kPa, microwave power was varied from 1.0 and 1.5 kW, respectively. Reaction time was fixed to 3 h. Silicon wafers which scratched by diamond powders were used as substrates. Surface and cross section of deposits were observed using SEM. Raman spectroscopy was used to estimate the qualities the deposits. As a result of SEM observation, particle size was about 3.0 mm and the film thickness was 2.0 mm for microwave power; 1.0 kW. However, particle size was about 5.0 mm and the film thickness was 14.0 mm for microwave power; 1.5 kW. The particle size and deposition rate were increased with increasing of microwave power. In addition, the diamond peak at 1333 cm-1 and DLC peak at 1550 cm-1 were observed in there Raman spectra of all samples. And the DLC broad peaks with a center around 1550 cm-1 were decreased with increasing of microwave power. As a conclusion, particles size and quality of films were effected microwave by power and quality of the film was improved at higher microwave power.
DP-9 Effects of the Substrate Setting Position on Diamond Growth Using Hot Filament CVD K. Watanabe (Chiba Institute of Technology, Japan) Investigation was carried out on the effects of the substrate setting position on diamond growth using Hot Filament CVD to understand basic knowledge about three-dimensional diamond coating. Mixture of CH₄ and H₂ was used as a reaction gas system. The synthesis pressure was 4.0 kPa, reaction time was 3 h and distance between the filament and the substrate was kept 3 mm. The substrate was set below the filament and above the filament when the filament was set horizontal. And the substrate was set beside the filament when the filament was set vertical. Estimation of deposits was carried out by Scanning Electron Microscopy (SEM) and Raman spectroscopy. As a result of SEM observation, particle was about 5 µm in diameter for below the filament, about 10 µm in diameter for beside the filament, and about 15 mm in diameter for above the filament. The grain size of the particle increased by changing the substrate position from below the filament to above the filament. For the estimation of deposits by Raman spectroscopy, the peaks of diamond and DLC were observed in Raman spectra of each sample. And inclusion of DLC decreased by changing the substrate position from below the filament to above the filament. It was clear that qualities of films were improved and the grain size of the particle was increased by changing the substrate position from below the filament to above the filament.
DP-10 The Effect of Nitrogen Addition on the Morphology and Quality of Boron-Doped Diamonds Grown by the Microwave Plasma-Assisted Chemical Vapor Deposition M. Nishitani-Gamo, K. Iwasaki (Toyo University, Japan); H. Gamo (Toppan Printing Co., Ltd., Japan); K. Nakagawa (Toyo University, Japan); T. Ando (National Institute for Materials Science (NIMS), Japan) We investigated the effect of a simultaneous addition of diborane and nitrogen on the chemical vapor deposited diamond growth. The doped diamonds were grown on Si substrates by the microwave plasma-assisted chemical vapor deposition (MPCVD) method. We used a mixture of hydrogen and methane as a reactant gas. For the boron doping, diborane (B2H6) gas was introduced in the range from 0 to 10 ppm in the gas phase. Nitrogen was introduced in the range from 0.0 to 2.0 %, as well. The input microwave power was 800 W. The substrate temperature was independently controlled from the plasma condition by using a substrate cooling/heating system placed in the substrate holder. The grown temperature was controlled in the range from 973 K to 1173 K. The effect of a simultaneous addition of diborane and nitrogen on the morphology was studied by a Scanning Electron Microscopic observation of the isolated diamonds. We also measured the micro Raman spectra of the diamonds to know the effect on the quality. The growth rate of the doped diamond was calculated from the thickness measured by a cross-sectional SEM observation of the grown film. With increasing of the N2 concentration in the gas phase above 0.4%, the morphology of the isolated diamonds varied from a cubo-octahedral shape to a sphere-like shape. The added small amounts of N2 in the gas phase gave a sphere-like crystal. Under the same N2 addition of 0.8% in the gas phase, a different B2H6 addition yielded a different morphology as following: In the case of the lower B2H6 concentration (2 ppm) in the gas phase, the isolated diamond crystals showed a sphere like morphology similar to that observed in the case of N2 addition alone. Contrary to this, at the higher B2H6 addition of 10 ppm in the gas phase, the isolated diamond crystals were in the form of a cubo-octahedral shapes. We found that the effect of nitrogen addition on the morphology decreased with increase of the B2H6 concentration in the gas phase.
DP-11 Ultra-Fine Patterning of the N-Doped CVD Diamond Films I. -N₂ Addition in the Gas Phase for Nano-Fabrication H. Gamo (Toppan Printing Co., Ltd., Japan); K. Shimada, M. Nishitani-Gamo (Toyo University, Japan); T. Ando (National Institute for Materials Science (NIMS), Japan) Diamond has attracted much attention because of its outstanding properties, such as its high hardness, high Young's modulus, high thermal conductivity, chemical inertness, wide band gap, and wide potential window. The applicable form of the diamond is usually to be a polycrystalline film grown by a chemical vapor deposition. The crystal size of these films is in the range from several to several-tens micrometers. For use the excellent potential of diamond films for wider applications, it is necessary to establish the fabrication technique of the diamond films for desired patterns. In order to fabricate diamond films with a nanoscale ordered ultra-fine pattern, it is essential to elucidate how the surface roughness, crystallinity, and crystal size of the diamond films affect the fabricated patterns. We have investigated how the growth conditions affected the crystallinity, the crystal size, and the surface morphology of polycrystalline diamond films grown by microwave plasma-assisted chemical vapor deposition (MPCVD) for use in a nanoscaled patterning process. As a reactant gas, methane (CH₄) and nitrogen (N₂)) diluted with hydrogen (H2) was used. The grown surface morphology was drastically changed by the addition of a small amount of N₂ in the range of 0% to 2.0% in the gas phase. The surface roughness of the diamond films showed a maximum value when the films were grown at an N₂/CH₄ flow rate ratio of 0.010, and above this ratio, it was sharply decreased. Atomic force microscopy revealed that the film grown using an N₂/CH₄ ratio of 0.100 had a minimum RMS value of 66 nm. The X-ray diffraction patterns revealed that a diamond film with a rougher surface showed a higher (220) / (111) intensity ratio. The reduction of surface roughness was caused by the decrease of the crystal size of polycrystalline diamond films.
DP-12 Ultra-Fine Patterning of the N-Doped CVD Diamond Films II. -Electron Beam Lithography- H. Gamo, N. Fukugami, A. Tamura (Toppan Printing Co., Ltd., Japan); M. Nishitani-Gamo (Toyo University, Japan); T. Ando (National Institute for Materials Science (NIMS), Japan) Diamond materials have specific properties applicable to mechanical, chemical, optical electronic, and electrochemical devices. For advanced practical applications, the diamond is generally used as thin-films on heterogeneous substrates such as silicon (Si). For example, an electrochemical sensor head, which is expected to be one of the most effective applications of diamond films, must be as small as possible for achieving the best detection limit. This necessitates the development of nano-scale diamond fabrication technique. For nano-scaled patterning utilizing the e-beam lithography method, the surface morphology of diamond films will affect the limit of resolution and the fine structure of the fabricated pattern. In this study, we have investigated the relation between the surface morphology of polycrystalline diamond films grown by microwave plasma-assisted chemical vapor deposition (MPCVD) on Si and the properties of nano-meter scaled ultra-fine patterning produced by utilizing e-beam lithography. One Âµm-thick polycrystalline diamond films of differing morphologies on 4 inch Si wafers were prepared by the addition of 0% (undoped), 0.1%, and 1.0% nitrogen in the gas phase, respectively, into 10% methane diluted using a hydrogen system during MPCVD. Surfaces rougher than Rms=45nm were observed in both undoped and 0.1% N-doped diamond films, therefore producing many protuberances on the edges of the fabricated linear patterns. On the other hand, in the 1.0% N-doped diamond film, which has a relatively small degree of surface roughness of Rms=18nm, an edge-roughness of 14nm in ultra-fine fabricated patterns was obtained. It was shown that the resolution and the edge-roughness on the nano-scaled ultra-fine patterns depended on the surface roughness of the polycrystalline diamond films.
DP-13 Preparation of CVD Diamond using RF Thermal Plasma K.O Onizawao (Chiba Institute of Technology, Japan) Chemical Vapor Deposition (CVD) using thermal plasma is well known as one of methods for high growth rate diamond synthesis. 4MHz RF power supplies of the self-oscillation were used for these methods generaly. However, stabilization of plasma was not satisfied for high growth diamond synthesis. In this report, generations of thermal plasma using 13.56MHz power supply of crystal-oscillation and diamond synthesis by thermal plasma were investigated. The mixture of H₂ and CH₄ as reaction gas and Ar as carrier gas were used to introduce the plasma torch. Si and Mo were used as substrates. Synthesis pressure was fixed to 520hPa and H2 flow rate was varied from 1 to 1.5SLM. CH₄/H₂ concentration was varied from 1% to 5%. Scanning Electron Microscope (SEM) and Raman Spectroscopy were used for evaluation of deposits. As a result, generation of the plasma was recognized from 260hPa to 780hPa. From the SEM observation, particles were observed in images of the deposits of each substrates and the particle size was increased with increasing of CH₄ concentration. In addition, a diamond peak at 1333 cm-1 and broad peaks of amorphous carbon around 1350 cm-1 and 1580cm-1 were observed in Raman Spectra. From the above result, thermal plasma can be generated by 13.56MHz power supply and diamond particles can be synthesized using this thermal plasma.
DP-14 Etching of Graphite in Atomic Hydrogen, a Simple Method for Characterization of Diamond CVD Chambers F. Faili, C. Engdahl, E. Francis (Crystallume) In an attempt to establish an empirical model for the characterization of diamond CVD chambers, graphite coupons were etched in atomic hydrogen. With the reported reaction path for graphite etching in atomic hydrogen as: C + 2H* ---> CH₂, CH₂ + 2H* ---> CH₄, graphite etch rates were quantified in response to variation in factors such as power, pressure, hydrogen flow, etc., and the establishment of process trends. To examine the validity of the graphite etching as a rough measure of trending for the diamond CVD process, a series of deposition tests were performed. The conditions of the deposition runs, were duplicate of the etching runs, with the addition of the methane gas and the use of silicon and/or tungsten carbide substrates. The graphite etch and diamond deposition trends were demonstrated to be in good agreement. With the typical etching time of thirty minutes or less per run, this novel approach for characterization of diamond CVD reactors is both simple and economical. A screening DOE matrix could be completed in a single day.
DP-17 Properties of CN Nanofibers Synthesized by Plasma-Enhanced Chemical Vapor Deposition J.H. Yang, J.I. Jeong (Research Institute of Industrial Science & Technology, Korea); M.H. Yum, D.H. Ryu, S.Y. Lee, W.S. Song, J.Y. Hong, C.-Y. Park (Sungkyukwan University, Korea) The morphology and the electronic structure of carbon nitride (CN) nanofibers synthesized by plasma-enhanced chemical vapor deposition have been investigated. A gas mixture of C₂H₂, NH₃, and N₂ was used as precursor, and Si(100) wafer coated with Ni and TiN, which were a catalyst and a buffer layer, respectively, was used as substrate. The growth temperature of CN nanofibers was 650°C. X-ray photoelectron spectroscopy and near-edge x-ray absorption fine structure spectra showed the existence of nitrogen molecules in CN nanofibers. Elemental mapping images with electron energy loss spectroscopy of the CN nanofiber showed that nitrogen atoms and molecules were distributed in the nanofiber and the catalyst. CN molecules were main source of carbon and nitrogen, which was investigated by optical emission spectroscopy. Through these results, it was concluded that atomic nitrogen diffused into the catalytic metal particle because of the concentration gradient and then saturated at the bottom of the particle. Saturated nitrogen atom participated in the formation of the CN nanofiber wall but most of nitrogen was trapped in the central hollow of the nanofiber as molecules. Also, this report suggested the growth mechanism of CN nanofibers.
DP-18 Formation of Beaded Vapor Grown Carbon Nanofiber J. Ting, Y. Chen, W. Wu (National Cheng Kung University, Taiwan) Vapor grown carbon nanofiber (VGNF) normally exhibits tree annual ring type of structure and has a hollow core whose diameter is influenced by the size of the catalyst particle used. Tubular VGNF also exhibit a bamboo-like structure where the hollow core is sectioned. Although effects of temperature on the growth and characteristics of VGNF have been investigated, these studies primarily focused on temperatures below 1200. A previous study reports the formation of beaded VGNF obtained at 1400. Beads were found along the length of the nanofiber. However, the formation mechanism was not reported. In this paper, we report the formation of another type of beaded VGNF and discuss the formation mechanism. The formation and frequency of the beads occurrence were both influenced by the growth conditions. The formation of such an unusual structure is related to the defect microstructures found in the nanofiber during growth and explained in terms of a three-dimensional nucleation model.
DP-19 Characterization of Amorphous CN_x Films Grown by Electrochemical Deposition Using Acrylonitrile Liquid H. Kiyota (Kyushu Tokai University, Japan); H. Gamo (Toppan Printing Co., Ltd., Japan); M. Gamo (Toyo University, Japan); T. Ando (National Institute for Materials Science (NIMS), Japan) Carbon nitride has been of great interest in developing superhard and wide band-gap material since theoretical prediction of β-C₃N₄ phase by Liu and Cohen. Therefore growth of carbon nitride has been extensively studied using conventional vapor-deposition techniques. In this work, we have attempted electrochemical deposition of carbon nitride films using nitrogen-containing organic liquid. The deposition of carbon nitride was carried out by application of DC bias to Si substrate immersed in acrylonitrile (CH₂CHCN) liquid. To clarify fundamental properties of the grown films, composition, bonding states and electronic structure of the films were studied using scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Continuous and uniform films are grown with the application of negative bias as well as with that of positive bias. The difference in surface morphology of the grown films is caused by the deposition parameters such as bias polarity during the film growth. Raman spectra of the grown films show two broad peaks at 1320 cm^-1 and 1580 cm^-1, indicating that a structure of the film is similar to that of amorphous carbon. The XPS survey spectra reveal a presence of C, N, and O atoms as major components of the grown films. Atomic ratio of nitrogen to carbon is estimated to be 0.16 - 0.24 in the films. From an analysis of C 1s and N 1s core-level spectra, major bonding states of a-CN_x films can be explained by a mixture of CN triple bond and hydrogenated C=N bond. The valence-band spectra show several peaks related to C-C π-bond, C-N π-bond, C-N σ-bond, C 2s and N 2s states, and a mixture of 2s and 2p states. In particular, the peak assigned to N 2s state and C=N bonds due to C 2p and N 2p electrons are found dominating the valence-band spectra of a-CN_x film.
DP-20 Synthesis and Structural Evolution of Boron Nitride Films and Nano-Structures P.C. Huang, M.S. Wong (National Dong Hwa University, Taiwan) Boron nitride films and nano-structures grown on nanocrystalline diamond films and silicon substrates were prepared under the reaction of B₂H₆ and NH₃ in H and Ar atmosphere in a microwave plasma enhanced CVD system. Boron nitride nano-structures (BNNS) of nano-rods, nano-tips, and nano-fibers were formed under low substrate bias about -100 V and their morphologies changed with the variation of layer thickness or substrate bias value. Fourier transform infra red spectroscopy and transmission electron microscopy studies confirmed that various phases of boron nitride in BNNS were formed including hexagonal (h-BN), turbostratic (t-BN), rhombohedral (r-BN), explosion (E-BN), wurzitic (w-BN) and cubic (c-BN) boron nitrides. In the field emission measurement, the turn-on field for BN nano-tips was 11.6 V/µmm, while the best turn-on field is 5.5 V/µm for BN nano-rods.
DP-21 Effects of Silver Content in MWNT Paste on the Carbon Nanotubes Field Emission Back Light Unit Properties S.F. Chen (National Taipei University of Technology, Taiwan); L.-K. Chang, S.-H. Lee (Industrial Technology Research Institute, Taiwan) In this work, effects of silver content in multi-walled carbon nanotubes (MWNTs) paste on the field emission properties were investigated for the application of carbon nanotube field emission back light unit (CNT-BLU) cathode. The diode cathode structures were fabricated by thick-film screen-printing technology, and TGA analysis was used to study relationship between CNT and silver during sintering process. By using adhesive tape to activate emitter surface, most of the carbon nanotubes (CNTs) can be aligned vertically. By constant-current measuring method, emission properties such as brightness, uniformity, emission intensity, can be examined. The surface morphologies were observed by field emission scanning electron microscopy. These results demonstrated that conductance was enhanced with increasing silver content in MWNT paste, but excess silver content degraded emission performance due to electric shielding effect.
DP-22 Field Emission Properties of Carbon Nanotubes Grown on a Conical Tungsten Tip for The Application of a Microfocus X-Ray Tube C.K. Park, S.J. Yun (Hanyang University, Korea); S.K. Kim (Korea Atomic Energy Research Institute, Korea); S.H. Heo, S.O. Cho (Korea Advanced Institute of Science and Technology, Korea); J.S. Park (Hanyang University, Korea) X-ray sources using cold cathodes have several intrinsic advantages over the thermionic x-ray tubes, including low operating temperature, instantaneous response time, and potential for miniaturization. Carbon nanotube (CNT), as an electron source for x-ray application, has attracted a great attention because of its high aspect ratio, high chemical stability, large current carrying capacity, and robust structure. Recently, a microfocus x-ray tube using CNT tips has been developed for the applications to high resolution x-ray imaging such as diagonal medical image and industrial inspection. The fabrication techniques for vertically-aligned CNT growth on a conical tungsten tip are very difficult and the current density of CNT tips decreases drastically with increasing emission time due to problems such as adhesion between a substrate and CNTs, uniformity, current suppression, and dispersion. However, there has scarcely been reported in literature regarding these issues. We present experimental results that regard the field emission properties of CNT-based emitters for a microfocus x-ray tube. The CNTs are successfully grown on a conical tungsten tip using the inductively coupled plasma-chemical vapor deposition (ICP-CVD) method. Tungsten wires with 250 µm diameter are conically etched using an electrochemical etching technique in 1 mol/l KOH. After cleaning the tungsten tips with 5 µm diameter in HF solution, TiN and Ni thin films are deposited by rf magnetron sputtering as a buffer layer and a catalytic material, respectively. Prior to growth of CNTs, NH₃ plasma etching has also been performed. For all the CNTs grown, nanostructures and morphologies are analyzed using Raman spectroscopy, FESEM, and HRTEM, in terms of the conditions of catalytic preparation and CNT growth. Furthermore, the field emission of CNT based-emitters is measured to characterize the maximum current density, lifetime, stability, and spatial distribution of electron beams.
DP-23 Thickness Effect on the Formation of SiC Nanoparticles in Sandwiching Structure of Si/C/Si Multilayers C.K. Chung, B.H. Wu, T.S. Chen, C.C. Peng, C.W. Lai (National Cheng Kung University, Taiwan) In this study, the effect of carbon and silicon thickness in sandwiching structure of Si/C/Si multilayers on a Si(100) substrate using ion beam sputtering (IBS) system under ultra high vacuum (UHV) to form SiC nanoparticles (np-SiC) were investigated by thermal annealing. The thickness of a deposited coating can be a critical factor in determining the particle size, density, and distribution of np-SiC after annealing temperatures of high vacuum annealing at 500, 700, 900 °C for 1.0 hour. Both carbon and silicon layer thickness on the microstructural evolution in three-layer Si/C/Si are sandwiching structures in different thickness i.e. 50/200/50 nm and 75/150/75 nm thin films. There were no nanoparticles formed for multilayers annealed temperatures at 500 °C. The np-SiC were formed by annealing multilayers of Si/C/Si precursors at around 700 °C. At an annealing temperature of 900 °C for Si/C/Si (75/150/75 nm), many nanoparticles appeared on the surface in polyhedral shape and density of about 1.8 times higher than that observed on Si/C/Si (50/200/50 nm). It is attributed to the thicker Si and thinner C thickness resulting in the increase of C and Si reaction to form np-SiC as well as the increase of np-SiC density. The np-SiC in Si/C/Si multilayers were examined by field emission scanning electron microscope (FESEM) for particle characterization, grazing incidence X-ray diffractometer (GIXRD) for phase identification and auger electron spectroscopy (AES) depth profile for the interdiffusion and reaction behavior. A mechanism for the np-SiC formation is proposed in this paper. Key words: SiC, nanoparticles, ion beam sputtering, multilayers.
DP-24 Mechanical Properties of a-C:H Films Deposited from Butadiene, Butene and Methane Gases by CVD Glow Discharge M.M.D. Michel (UFPR, Brazil); P.J.G. Araújo, C.A. Achete, C.M. Lepienski (Universidade Federal de Rio de Janeiro, Brazil) Mechanical properties of hydrogenated amorphous carbon (a-C:H) thin films deposited by chemical vapor deposition (CVD) from 1-3-butadiene, 1-butene and methane gases on silicon (100) substrates were investigated. It was measured the influence of the gas type, the chamber pressure, and the voltage bias on hardness, elastic modulus, deposition rate and residual stress of the films. The chamber pressure was set to 2 Pa and 8 Pa, while the voltage self bias was varied from -60 V to -400 V. Hardness and Elastic modulus were measured by depth sensing indentation with a Berkovich indenter. The residual stress of deposited films was determined using a profilometry technique. The experimental results indicate all films presented a compressive residual stress varying from -0.5 GPa to -5.0 GPa. Hardness and elastic modulus showed a strong dependence with origin gas, voltage bias and chamber pressure. It was found a maximum hardness of about 23 GPa for methane and butene films on specific deposition conditions. Films deposited at 8 Pa were softer than deposited at 2 Pa for all voltage bias. An almost linear increase of hardness and elastic modulus is observed with increasing voltage bias until they reache a plateau at the maximum value for films deposited from methane and butene. Films deposited from butadiene did not reaches a plateau of hardness. Probably the voltage bias in this work were not high enough to this occurs. Films deposited from butadiene were significantly softer than from butene despite both gases have 4 carbon atoms. Gas reactivity under CVD tends to form a more polymer like film for butadiene than for butene. However an increase on voltage bias can induce formation of DLC films also from butadiene.
DP-27 Wear Resistance of Ni-P-Diamond Composite Coating X. Hua (FuZhou University, China) Composite coating consist of diamond in Ni-P matrix had been developed for improved wear resistance. The effect of particle size, particle content in electrolyte, heat-treatment temperature and abrasion loading on the wear resistance of coatings was investigated. Results show that The Ni-P-micro-diamond composite coating presents the best wear resistance. Adding nano-diamond has little effect on the wear resistance of Ni-P coating. The wear resistance of Ni-P-micro-diamond composite coating shows a steady change with heat-treatment temperature and abrasion loading, while the wear loss of Ni-P coating and Ni-P-nano-diamond composite coating changes obviously with the temperature and loading. The main wear mechanism of Ni-P-micro-diamond composite coating is abrasion under all the loadings applied, while adhesion appear for the Ni-P coating and Ni-P-nano-diamond composite coating when the abrasion loading exceeds 10Kgf. Based on which, the abrasion mechanism is also discussed.

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