ICMCTF2008 Session TSP: Symposium TP Poster Session

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

Thursday Afternoon

Time Period ThP Sessions | Topic TS1 Sessions | Time Periods | Topics | ICMCTF2008 Schedule

TSP-1 Characteristics of Dye-Sensitized Solar Cell with Ionic Liquid Electrolytes Containing Carbon Nanotubes M.J. Park, S.U. Lee, B. Hong (Sungkyunkwan University, Korea) The dye-sensitized solar cell (DSSC) has been widely investigated as a cost effective device alternative to photo conversion solar cells. Generally, the iodine-doped ionic liquids or organic solvents are used as the electrolytes for DSSC. The electron mobility in electrolyte is considered to be an important factor to improve the efficiency of DSSC and most electrolytes have had the limitation in photo-current because of the low diffusion coefficient caused by the tri-iodide. The electrolyte of AN50 used in this work exhibited low viscosity and had 50 mM of tri-iodide. This electrolyte was modified by mixing CNTs with the AN50 electrolyte to improve the limitation mentioned above. CNTs mixed with the electrolyte were multi-wall carbon nanotubes (MWCNT, CMP-series, Diameter: 4~12 nm) and single-wall carbon nanotubes (SWCNT, ASA 100 F, Diameter: 10 nm), respectively. We investigated the variation of the energy conversion efficiency with the concentration and type of CNT. The ionic liquid electrolyte containing CNT tends to increase the efficiency with the CNT concentration and the efficiency of DSSC containing the MWCNT in the electrolyte is higher than that of DSSC containing SWCNT. In the result, the high conductivity of CNT inside the electrolyte contributes to the efficiency of DSSC owing to the improvement of the transport and recombination of electrons.
TSP-2 Characterization of Tungsten-Titanium Oxide Electrode for Application in Dye-Sensitized Solar Cells K.-W. Weng (Mingdao University, Taiwan); S. Han (National Taichung Institute of Technology, Taiwan); Y.-C. Chen (National Chung Hsing University, Taiwan) Recently, with the working electrode for dye-sensitized solar cells (DSSCs), titanium oxide was studied. The substrate, a conductive glass being coated indium tin oxide (ITO) thin films, deposited tungsten-titanium oxide using radio frequency (RF) sputtering in this study. The optical properties and thickness of oxide films were determined by measured transmittance. Compared with the titanium oxide electrode, the tungsten-titanium oxide electrode showed good characteristics such as decreasing in band gap and increasing in conversion efficiency. The relationship between the film thickness and both the open-circuit voltage and the short-circuit current is also discussed.
TSP-3 Comparison of Photocatalytic Activities of Various Dye-Sensitized TiO₂ Thin Films Under Visible Light K.S. Yao, T.C. Cheng, S.J. Li (Mingdao University, Taiwan); K.C. Tzeng (National Chung-Hsing University, Taiwan); Y. Ko, C.Y. Chang (Mingdao University, Taiwan) Owing to its large band gap energy of 3.2 eV, pure TiO₂ film operates as an efficient photocatalyst only under UV light irradiation and exhibits no photocatalytic activity under the visible spectral region. However, UV is only about 3% of the light existing in the solar spectrum. Currently, the red-shift in the band gap energy induced by dye-sensitized TiO₂ film is one of the most popular and economic processes to improve the drawback of TiO₂ photocatalyst. Therefore, we assess the photocatalytic efficiency of dye-sensitized TiO₂ thin film with various dye molecules such as Eosin Y, Safranine O and tris-2, 2' -bipyridyl dichlororuthenium (II) hexahydrate (Rubpy) using sol-gel process under visible light (?>400 nm). These results showed that the TiO₂ thin film sensitized with Safranine O dye had the best photodegrading efficiency under visible light irradiation. Meanwhile, the photocatalytic inactivation of Safranine O dye-sensitized TiO₂ thin film against plant pathogenic bacteria including Enterobacter cloacae SM1 and Erwinia carotovora subsp. carotovora 3 which caused severe soft/basal rot disease in vegetable crops were all more than 90% after 60 min visible light illumination. These evidences suggest that the dye-sensitized TiO₂ thin film under visible light irradiation has a potential for application to plant protection in hydroponics system.
TSP-4 Photocatalytic Bactericidal Effect of TiO₂ Thin Film on Fish Pathogens T.C. Cheng, C.Y. Chang (Mingdao University, Taiwan); C.I. Chang (Aquaculture Division, Fisheries Research Institute, Taiwan); C.C. Hwang, H.H. Shu, D.-Y. Wang, K.S. Yao (Mingdao University, Taiwan) Diseases are the major hinder for the development of aquaculture industry and antimicrobial agents are always used to treat bacterial disease. However, few antimicrobial agents are allowed for use in aquaculture due to concerns of developing resistant pathogens and food safety on farming organisms. Therefore, ultraviolet (UV) light has long been used to disinfect bacterial pathogens in re-circulated water system used in hatchery and pond. Recently, the bactericidal effects of UV-radiated TiO₂ on human pathogens are found significantly more efficient than using UV along but their efficiencies on fish pathogens remain to be studied. TiO₂ are synthesized using sol-gel method. Their particle size and crystal structure are characterized using scanning electron microscope (SEM) and X-ray diffractometry. The fish bacteria pathogens of Aeromonas hydrophila, Edwardsiella tarda and Streptococcus iniae causing great fish farming loss in subtropical regions of Asia are deposited on glass coated with TiO₂ and radiated with UV-A for various time intervals. The bacteria mortality is estimated using 2, 3, 5-triphenyl tetrazolium chloride (TCC) and the morphology of bacteria are recorded using SEM. The results demonstrate that mortalities of fish bacteria pathogens are significantly higher in UV-A radiated TiO₂ thin film groups than those of UV-A radiated only groups. Regardless of fish pathogen species, more than 90% mortalities are found in groups of 60 minutes UV-A radiated TiO₂ thin film. Decomposing bacterial surfaces are found in all but control groups. In conclusion, UV-A radiated TiO₂ thin film is more efficient than UV-A in bactericidal effects on fish pathogens.
TSP-5 Preparation of LaCrO₃ Coatings on Stainless Steel by Magnetron Sputtering Process W.-Y. Ho, M.-H. Tsai, C.-L. Chang, D.-Y. Wang (Mingdao University, Taiwan) Chromium-containing stainless steel is a prospective material for use as an interconnect in solid oxide fuel cells (SOFCs). However, during operations at high temperatures, the growth of oxide scales causes the deteriorated performance of the SOFC. In this study, in order to improve the performance of stainless steel as interconnect material, the deposition of La-Cr-O coatings on stainless steel was conducted with dual targets of La and Cr by using magnetron sputtering process. During the deposition process, the Cr and CrN were first deposited, respectively, as interlayers to protect the stainless steel from further oxidation during high temperature operation. Owing to using sputtering process, the as-deposited La-Cr-O coating exhibited with amorphous structure in nature, however, after annealing treatment at 800°C for 1 hour, the LaCrO₃ perovskite phase was obtained. During the annealing of the material in air a two-step phase transition from La-Cr-O to a monoclinic LaCrO₄ monazite and further to an orthorhombic LaCrO₃ perovskite phase was observed. The formation of a fine nanoporous structure is a result of the significant increase in density of the final LaCrO₃ perovskite in comparison with monazite LaCrO₄ phase. Dynamic oxidation of La-Cr-O coated stainless steel studied by using thermo-gravimetric analysis (TGA) and differential scanning calorimeter (DSC) confirms that the better oxidation resistance and electrical resistance of the La-Cr-O-coated stainless steel during isothermal heating process. This was attributed to the transformation of coating from amorphous to LaCrO₃ perovskite structure, resulting in a better performance after heating up to 800°C.
TSP-6 Osteoblast Behavior on Plasma-Treated Medical Polyethylene H.Y. Wang, Z. Wei, P.K. Chu (City University of Hong Kong) Medical polyethylene (PE), which is one of the most popular medical polymers, still suffers from insufficient biocompatibility after implantation into the human body. In this work, Ar, O₂, H₂O, N₂, and NH₃ plasma immersion ion implantation (PIII) is conducted to modify the PE surface and hFOB 1.19 cells are used as the osteoblast model to investigate the osteoblast compatibility of PE. Our results show that osteoblast adhesion is enhanced and the effectiveness follows the following order: O₂ PIII - H₂O PIII > Ar PIII - NH₃ PIII > N₂ PIII. The similar hydrophilicity and surface morphology of PE after PIII treatments of different gases suggest that the different cell behavior stems from the different surface chemistry introduced by PIII. Ar PIII, O₂ PIII, H₂O PIII, N₂ PIII and NH₃ PIII are observed to lead to the formation of C=C, C=O, C-OH, C=NH/C=N and C-NH₂ groups on the PE surfaces, respectively. The C=O and C-OH groups on PE have a positive effect on osteoblast adhesion, whereas C=NH/C=N affects osteoblast adhesion negatively and the impact of C=C and C-NH₂ is in between. Our results suggest that O₂ and H₂O PIII are effective methods to enhance osteoblast adhesion on medical PE.
TSP-7 La_0.67Sr _0.33MnO₃ Coating on SOFC Interconnect by Plasma-Sputtering C.L. Chu, S. Lee (National Central University, Taiwan) Solid oxide fuel cells (SOFCs) are developed to meet the energy requirements of the society. Due to high operating temperatures (800-1000°C), the material selection for SOFC is an important aspect of its design and development. Among the four essential components of SOFC; anode, cathode, electrolyte, and interconnect, materials selection for interconnects is a critical factor. Five metallic alloys, namely, Crofer22, equivalent ZMG232, stainless steel SS430, SS304 and Inconel718 were investigated. A La0.67Sr 0.33MnO3 (LSMO) thin film is coated on these materials using pulsed DC magnetron sputtering. The film is amorphous but transformed to perovskite structure after annealing at 600°C, 700°C, 800°C and 900 oC for 1hr. Then the resulted oxide scale was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The result shows the LSMO thin film on Crofer22 and equivalent ZMG232 were good for compaction and adhesion. Thus, it could prevent the growth of oxide and the diffusion of Cr element to avoid poison of the cathode and decline of conductivity in SOFC in high temperature. In addition, the coated Crofer22 and equivalent ZMG232 were tested for the area specific resistance (ASR) measurement in 800°C for 1000hrs to observe the variation of contact resistance.
TSP-8 Protein Activity of the Protein-Nanodiamond Conjugates Prepared for Bio Labeling Using Nanodiamond P.J. Cai, E. Perevedentseva, Y.C. Chiu, P.H. Chung, C.L. Cheng (National Dong Hwa University, Taiwan) Nanometer-sized diamond particles have recently been proven to be an effective nano-material for bio and medical applications. The unique natural fluorescent and Raman properties combined with its superb biocompartibility render it possibillity to replace the conventional quantum dots. However, for use as a biolabeling nanomaterial, the functionality of the conjugated bio molecules, such as protein, needs to be preserved for any sensible application. In this work, we prepared protein Lysozyme and carboxylated nanodiamond complex (labeled as Lyso-cND) and investigated various properties of this complex including IR, Raman and the surface charges distribution of the complex. The interaction of this complex with bacteria E. coli was observed using both Raman mapping and scanning electron microscopy. The functionity of Lyso-cND complex was further tested with Lysozyme Assay kit (E22013) to measure the levels of lysozyme activity in solution when the lysozyme is conjugated with nanodiamond. All these tests and observations confirmed lysozyme did not loss it functionality when conjugated with nanodiamond. This comprehensive study demonstrated nanodiamond can be used as an effective nanoparticle for bio-labeling.
TSP-9 Characteristic of Gradient SOFC Anode Synthesized by the Co-Sputtering of Magnetron Sputtering and Cathodic Arc Evaporation C.C. Chu, D.-Y. Wang (Mingdao University, Taiwan) In order to develop a high-performance solid oxide fuel cell (SOFC), a Ni/YSZ anode with a gradient composition deposited on the surface of the YSZ electrolyte was investigated in this research. Besides the total surface area of TPB in an sofc anode , a good efficiency of an sofc anode is highly related with its component distribution .The anode layer closer to the electrolyte should contain primary YSZ which served as the matrix support for Ni particles and maintain matching coefficient of thermal expansion with the electrolyte. On the other hand, the anode layer in the anode away from the electrolyte should contain higher amount of Ni particle in order to have good electrical contact with the interconnector. To accomplish this purpose, physic vapor deposition was employed to synthesize the electrolyte and the anode structure of an SOFC.A dense 8mol% yttria-stabilised zirconia electrolyte on the LSM cathode was deposited by magnetron sputtering. Subsequently , the anode with gradient Ni/YSZ content distribution was co-deposited on the surface of the electrolyte by cathodic arc evaporation and magnetron sputtering technique. After reduction of the anode in hydrogen , the cross-section of the anode revealed the gradient content of Ni and YSZ .Ni crystallites as well as YSZ phases were revealed by XRD analysis . The power generation characteristics of the SOFC single cell was demonstrated by the I-V curve measurement and an Arbin SOFC test station.
TSP-10 Control of Preferred Orientations of TiN and ZrN Thin Films by Thin Film Templates Y.-Y. Cheng, J.-H. Huang, G.-P. Yu (National Tsing Hua University, Taiwan) TiN and ZrN are widely used thin film materials in industry due to their high hardness, high thermal and chemical stabilities, and low electrical resistivity. Previous studies have reported that properties of thin films are strongly affected by the preferred orientations of the thin films, and therefore, control of preferred orientation of thin films is one of the key issues in the application of thin films. In this study TiN and ZrN thin films were deposited on Si(100) using an unbalanced magnetron sputtering (UBMS) system. In order to control the preferred orientation of the thin films, we prepared a Ti(N,O) thin film with (200)-dominated orientation as the templates. The purposes of this research were to investigate the effectiveness of the template on the control of preferred orientations of TiN and ZrN films and to explore the effect of template thickness on the validity of orientation control. The properties changes of the thin films due to varying preferred orientation were also investigated. The preferred orientations and grain size of the thin films were determined by X-ray diffraction (XRD). The residual stress of the films was determined by optical method and the modified sins ²ψ method. The results showed that the preferred orientations of the TiN and ZrN films changed from (111) to (200) in the presence of template. The Ti(N,O) template has stronger effect on TiN films than ZrN films. The specimens with template sustained compressive residual stress which increased with the thickness of TiN and ZrN films. In general, the template was useful to control the preferred orientations of TiN and ZrN films and to change the films properties.
TSP-11 Inductively Coupled Plasma Nitriding for PEMFC Bipolar Plate D.H. Han, B. Park, W.H. Hong (Seoul National University, Korea); W.Y. Jeung (Korea Institute of Science and Technology, Korea); J.J. Lee (Seoul National University, Korea) AISI316 stainless steel is one of the candidates for polymer electrolyte membrane fuel cell (PEMFC) bipolar plate because of its low cost and suitability for manufacturing. However, interfacial contact resistance (ICR) and corrosion property of untreated AISI316 are not enough to be used in PEMFC operating conditions. In this study, we applied plasma nitriding process to improve the surface performance of AISI316 steel and chromium electroplated AISI316 which can improve corrosion property. After these surface modifications, we measured interfacial contact resistance and polarization curve in the simulated PEMFC environment. These results show that interfacial contact resistance is decreased and corrosion property is improved. The role of Fe, Cr nitride species and microstructural change were discussed considering XRD and SEM results.
TSP-12 The Influence of Surface Energy on Pentacene Growth Mechanism and on OTFT Characteristics H.W. Zan, C.-W. Chou, K.-H. Yen, C.-L. Wu (National Chiao Tung University, Taiwan) This study elucidates the pentacene-based organic thin film transistors (OTFTs) fabricated on the SAM-treated dielectric with various surface energies. The patterning of pentacene by adjusting the surface energy was also demonstrated. The surface energy was modified by self-assembled monolayer treatment followed by ultra-violet (UV) light exposure through a quartz-glass mask. After pentacene deposition, the growth mode of pentacene on surfaces with various surface energies was analyzed by Atomic Force Microscope (AFM). The morphology of pentacene grown on different surface with various thicknesses was carefully studied. The pentacene patterning was also achieved by using water dipping to remove the pentacene film grown on hydrophilic surface. OTFTs with pentacene grown on various surface were fabricated and characterized. When the surface energy was decreased, device mobility was enlarged from 0.07 cm²/Vs to 0.34 cm²/Vs and the threshold voltage was shifted from -16.27 V to -20.92 V.
TSP-14 Studies on Corrosion Resistance of Stainless Steel Bipolar Plates for Fuel Cell by High Temperature Nitrogen Implantation K.K. Kim, J.S. Kim (Pusan National University, Korea); S.M. Moon (Korea Institute of Machinery & Materials, Korea); J.S. Lee (Korea Atomic Energy Research Institute, Korea); M.C. Kang (Pusan National University, Korea) Ion implantation is a novel surface modification to enhance the mechanical, chemical and electrical properties of substrate surface using high energy ions. Metallic bipolar plates for the proton exchange membrane fuel cell offer many advantages over conventional graphitic materials. These include relative low cost, high strength, and ease of manufacture. As a metallic bipolar plate can be easily shaped from thin sheet with complex shape, significant improvement in the fuel cell power/volume ratio can be achieved. However, corrosion of the metallic bipolar plates is a severe problem. Corrosion affects the performance and lifetime of a fuel cell. The research on surface modification has been advanced to improve the properties of engineering materials. This experiment was performed in the high temperature in order to increase the implanted depth. The samples are implanted with 50~120 keV N-ion at substrate temperature ranging from 50~400?. Nano-hardness and AES(Auger electrons spectroscopy) were measured from nitrogen ion implanted layer. The sliding wear and impact wear properties of ion implanted samples depend strongly on the ion doses and implantation temperature.
TSP-15 Silanol/pHEMA Hybrid Membrane for Drug Controlled Release Y.-Y. Liu, C.-H. Tsai, S.Y. Chen (National Chiao Tung University, Taiwan); T.-Y. Liu (Mingchi University of Technology, Taiwan) The interconnection of inorganic and organic ingredients by either chemical, or physical interaction upon in-situ polymerization provides not only a featured nanostructure in the resulting hybrid, but also correspondingly offers unique properties that are frequently not able to achieve through individual components. Here, Silanol/pHEMA hybrid membrane was prepared by the hydrolysis of alkoxysilanes and used as matrices. The drug released profile of silanol/pHEMA hybrid could be controlled by varying the silanol degree and the hydroxyl groups which was determined by varying the hybrid composition and the water content in the sol-gel process. Morphology of the hybrid was characterized using optical microscopy (OM) and scanning electron microscopy (SEM) techniques. Fourier transforms infrared spectroscopy was also tested.
TSP-16 Bioactivity of Cu/pHEMA Coatings Prepared by Electrodeposition on Stainless Steel 316 for Implant Applications Y.-Y. Liu (National Chiao Tung University, Taiwan); T.-Y. Liu (Mingchi University of Technology, Taiwan); S.Y. Chen (National Chiao Tung University, Taiwan) The electro-catalyst and bioactive properties of copper used for biomedical devices has been attracting attention recently. The incorporation of copper into hydrogel such as poly(2-hydroxyethylmethacrylate) (pHEMA) may allow the extensive application of the composite. The excellent biocompatible properties of pHEMA material and the beneficial characteristics of Cu as a bioactive material and the positive effect of composite on cellular behavior were the motivation to investigate. In this study, the bioactive thin film of Cu/pHEMA was prepared by electrochemical polymerization of pHEMA and electrochemical reduction of copper ion on stainless steel 316. The electrochemical preparation method presents several interesting advantages such as the initiator in the reaction system can be easily controlled by cathodic current and the eaction can be terminated at will by stopping the cathodic current. The electro-initiated polymerization of HEMA mediated by titanium(III)-hydroxylamine sulfate in sulfuric acid-N,N-dimethylformamide (DMF) medium was used in this article. Morphology of the composite was characterized using optical microscopy (OM), scanning electron microscopy (SEM) techniques. Fourier transforms infrared spectroscopy, X-ray diffraction patterns, confirm the copper particle formation on nanocomposite. The in vitro blood compatibility properties of the composite were tested. This indicates that the coating of Cu/pHEMA composites could be used as anti-clotting material.
TSP-17 Nucleation of Ni and Ru Nano-Cluster Thin Films on Doped (La,Sr)CrO₃ Anode Surfaces S.A. Barnett, W. Kobsiriphat, B.D. Madsen, Y. Wang, L. Marks, M. Shah, P.W. Voorhees (Northwestern University) Solid oxide fuel cell anodes containing La_{0.8√sub 0.2}Cr_1-yX_yO_3-d (X = Ni or Ru), were studied. Transmission electron microscope and x-ray photoelectron spectroscopy observations showed that nano-clusters of Ni or Ru metal precipitated onto the lanthanum chromite surfaces after exposure to hydrogen at 800C. SOFC tests were done with the doped lanthanum chromite anodes on LSGM electrolyte-supported cells. Ru nano-cluster nucleation improved cell performance over the first ~100 h of cell operation, e.g., increasing power density from ~200 to 500 mW/cm2 and reducing anode polarization resistance from ~0.6 to < 0.2 Ohm cm2 at 800C in humidified hydrogen. Cell power density was reasonably stable from ~100 to 300 h for Ru. Ni nano-clusters had less impact on cell performance. The nucleation process appeared to be similar to the Volmer-Weber process expected for metals on oxide surfaces, except that the metal species arrived at the surface via diffusion from within the oxide material, rather than from the vapor. While Ni nano-clusters coarsened to ~ 50 nm over ~300 h at 800C, Ru nano-cluster size was stable at ~ 5 nm. Modeling of the metal cluster nucleation and growth, and implications for long-term anode performance, will be discussed.
TSP-18 Protein Adsorption on Low Temperature Alpha Alumina Films for Surgical Instruments A.N. Cloud (University of Arkansas); S. Kumar (University of South Australia); M Kavdia, H.H. Abu-Safe, M.H. Gordon, D.G. Bhat (University of Arkansas) Alumina is a biomedical material generally classified as bioinert. Compared to polymeric biomedical materials such as silicones and some metals/alloys, bulk alumina has been shown to exhibit reduced protein adsorption, a property that can be exploited for developing alumina-coated surgical instruments and devices. The residual (protein) bioburden on such coated surfaces is expected be relatively low and easy to remove, a feature highly desirable for reducing costs in the health care industry. Very little is known about protein adsorption characteristics of alpha alumina thin films. In this work alpha alumina thin films were deposited on surgical stainless steel substrates to investigate the adsorption of a model protein (BSA, bovine serum albumin). The films were deposited at 350°C by AC inverted cylindrical magnetron sputtering. Films of varied thickness (100 nm and thicker) were obtained at different power levels (4, 5, and 6 kW) and various oxygen partial pressures (40, 50, and 60 percent by volume). Alpha phase has been determined by transmission electron microscopy. Preliminary tribological testing of film adhesion and wear resistance indicate satisfactory performance of the coatings. Ongoing work to quantify residual protein levels both with and without the alumina coating will be presented in the full paper.
TSP-19 Study on Ultrasound-Sensitive NOCHC-Cu Nanohybrid as a Novel Drug-Loaded Coating for Delivering Hydrophobic Agents T.-Y. Liu (Mingchi University of Technology, Taiwan) Stimuli-sensitive biomaterials as drug-loaded implants and drug-eluting coatings are becoming increasingly important for biomedical devices. The key successful point of the drug-loaded stimuli-sensitive device is the sufficient sensitivity to environmental stimuli in controlling release of therapeutic agents, but also the controlled background leakage of agents to lower the side effect. However, it is very difficult to overcome the background leakage for the polymer-based and lipid-based materials. Recently, a novel chitosan derivative (N,O-carboxylmethyl hexanoyl chitosan, NOCHC) has been developed in our group to encapsulate partially hydrophobic agents such as ibuprofen, paclitaxol and doxorubicin. In addition, it is known that copper ions are useful in wound and skin care. On this basis, a novel drug-loaded coating can be prepared via incorporating Cu particles into NOCHC matrix through the reduction method. Preliminary study showed that the extent of background leakage was decreased while Cu nanoparticles were incorporated because copper ions acted as a crosslink agent and diffusion barrier. On the other hand, it was found that an ultrasound-sensitive behavior can be achieved via manipulating the nanostructure of the NOCHC-Cu nanohybrid. Moreover, the NOCHC-Cu nanohybrid demonstrated cell and blood compatible characteristics which are very suitable for the drug-loaded coating onto wound dressing material and vascular stent, respectively. These results demonstrated that the newly organically modified nanohybrid with an ultrasound-sensitive behavior can be employed as a smart coating material to encapsulate the partially hydrophobic agents for biomedical applications.
TSP-20 The Simulation of Molecular Dynamics Associate With the Surface Roughness on an Aluminum Thin Film Y.Y. Cheng, C.C. Lee (National Central University, Taiwan) Rough surface formation in thin films during annealing occurs with several materials. Increased roughness of an aluminum (Al) thin film surface can lead to electrical shorts, which are a significant problem for interconnections in liquid-crystal displays. Surface roughness can be decreased by adding a small amount of other metal into Al thin film. However, the mechanism through which roughness is decrease by an alloy is not well understood. This work simulates 3D molecular dynamics of Al thin film growth to determine whether surface roughness and substrate temperature are correlated. The interaction between Al atoms is the embedded-atom-method (EAM) potential. Simulations were performed with the substrate temperatures of 300-700K. Thin film surface roughness decreases as substrate temperature increases from 300K to 600K. Nevertheless, film surface roughness increases abruptly at 700K. Simulation results are in a good agreement with other published experimental results. To investigate the effects of adding tantalum (Ta) atoms on Al thin film surface roughness, simulations of Al thin film growth with different amounts of Ta atoms and a substrate temperature of 700K were performed. The Ta atoms were blended into the Al thin film uniformly during thin film growth. The addition of Ta atoms decreases thin film surface roughness. Furthermore, surface roughness decreases as the amount of Ta atoms in the Al-Ta alloy thin films increases. However, surface roughness increases with when Ta content exceeds 4 at.% Ta. Simulation results demonstrate that the saturation point for Ta atoms for surface roughness in Ta-Al alloy thin films is same as that obtained experimentally.
TSP-21 Adhesion and Preoesteoblastic Cell Proliferation in Titanium Surface Bombarded with Argon Ions C. Alves Junior (UFRN, Brazil) Titanium surfaces were modified by argon ions bombardment by means of the hollow cathode technique with the aim of evaluating the influence of this treatment on the cell-surface interaction. The effects of topographic (roughness, microstructure) and physiochemical (wettability - contact angle) parameters on (the) morphology, adhesion and MC3T3-E1 preosteoblasts proliferation were analyzed. No-treated surfaces (flat) were used as a control. The levels of roughness observed in modified and flat titanium surfaces were of 0.11µm and 0.027µm respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis showed that the roughness distribution was uniform. The wettability was larger in treated surfaces. The number of attached cells (30 and 60min) was significantly higher on the bombarded surface. The cell proliferation after 3 and 7 days was also significantly higher on ion-bombarded surface. The results demonstrated above allow us to consider the bombardment with argon ions utilizing the hollow cathode technique an excellent procedure for obtaining biomaterials that improve the osseointegration.

Time Period ThP Sessions | Topic TS1 Sessions | Time Periods | Topics | ICMCTF2008 Schedule