ICMCTF2008 Session HP: Symposium H Poster Session

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

Thursday Afternoon

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

HP-1 Characterization of Electrospun Aluminum Doped Zinc Oxide Nanofibers D.Y. Lee (Daelim College of Technology, Korea); N. Cho (Sunmoon University, Korea); M.H. Lee (Korea Institute of Ceramic Engineering and Technology, Korea); S.J. Lee (Kyungsung University, Korea); B.Y. Kim (University of Incheon, Korea) Al-ZnO nanofibers with diameters of 150~600 nm were prepared by using electrospun PVA/zinc acetate-aluminum chloride composite fibers by drying for 8 h at 60°C in vacuum and subsequent annealing for 1 h at temperatures in the range of 500 to 800°C in air. The properties of Al-ZnO fibers were characterized by varying PVA concentration with an aid of XRD, DSC/TG, FT-IR, SEM, TEM, viscometer, pycnometer and dynamic tensiometer. Uniform and smooth fibers with a diameter of 150 nm were observed for the electrospun fibers containing PVA amount of 40g at a calcination temperature of 600°C, a flow rate of 0.05 ml/h and an electric field of 0.95 kV/cm. Experimental results suggested that the calcination temperature was most influential on the fiber morphology and size.
HP-2 Dissolution of Cu Nano-Particles and its Implication on the Anti-Bacterial Property of TaN-Cu Nanocomposite Thin Films P.C. Liu, J.H. Hsieh (Mingchi University of Technology, Taiwan) Previous study shows that TaN-Cu nanocomposite thin films can have anti-wear and anti-bacterial properties. Both properties are dependent on the size and density of the surfaced Cu particles. The present study made an attempt to explain the relationship between the dissolving rate of Cu particles and the films’ antibacterial behavior. Firstly, Cu particles with different sizes were used to study the size effect on their dissolving rate. The results were then used to correlate the anti-bacterial behavior of TaN-Cu nanocomposite prepared under various conditions. It is found that those films with smaller Cu particles could have a faster anti-bacterial effect. This implies a possible application of these films on a device that requires short-term anti-bacterial effect. Electrochemical testing and ICP spectrometer were used to examine the dissolution rates of Cu particles.
HP-3 High-Power Pulsed Reactive Magnetron Deposition of TiN Films K. Burcalova, B. Zustin, J. Vlcek, J. Lukas (University of West Bohemia, Czech Republic) High-power pulsed reactive magnetron deposition of TiN films on Si(100) and steel substrates was investigated. The repetition frequency was in the range from 1 to 20kHz at a fixed 20% duty cycle, a total gas pressure of 1Pa and a substrate temperature of 400°C. Time evolutions of the discharge characteristics were measured in a 90%Ar+10%N₂ gas mixture at a target power density in a pulse up to 460W/cm². Time-averaged mass spectroscopy was performed at a substrate position located 100mm from the target. It was shown that argon ions are strongly dominant (68-85%) in total ion fluxes onto the substrate. With increasing preset average pulse currents at a fixed 10kHz frequency and with increasing frequencies at a fixed average pulse current, the ion energy distributions were more extended to higher energies (up to 50eV relative to ground potential). The increasing ion energies and fluxes, together with the increase in the N⁺/N₂⁺ ratio, resulted in changes in structure and mechanical properties (hardness up to 27GPa) of the prepared TiN films.
HP-4 Formation and Nonvolatile Memory Application of Ge Nanocrystals Using Si_1.33Ge_0.67O₂ and Si_2.67Ge_1.33N₂ layer W.-R. Chen (National Chiao Tung University, Taiwan); T.-C. Chang (National Sun Yat-Sen University, Taiwan); C.-Y. Chang, Y.-T. Hsieh (National Chiao Tung University, Taiwan) The author proposed a formation mechanism of Ge nanocrystals embedded in the dielectric by using Si_1.33Ge_0.67O₂ and Si_2.67Ge_1.33N₂ film for nonvolatile memory application in this study. Because of internal competition reaction, this formation process reduced the thermal budget and eliminated the use of high pressure H₂ treatment or steam process. The metal/oxide/insulator/oxide/silicon capacitor structure with nanocrystals was also studied and exhibited hysteresis characteristics after electrical operation. Transmission electron microscope clearly shows the shape and density of nanocrystals in the dielectric. In addition, the obvious memory window can be used to define "1" and "0" states at low voltage program operation. Furthermore, good endurance and retention characteristics are exhibited for the Ge nanovrystal embedded in SiN_x structure. Besides, the ease technology is suitable for the current nonvolatile memory fabrication and low power device application.
HP-6 Electron Field Emissions, Cathodoluminescence and Characterization of ZnO:Al Nanowires C.-W. Fang (National Chung-Hsing University, Taiwan); J.-M. Wu (Feng-Chia University, Taiwan); L.-T. Lee (National Chung-Hsing University, Taiwan) ZnO:Al nanowires were successfully synthesized on silicon substrates and glass substrates. The source material of Zn power was mixed with Al powder, and was thermal reactive evaporation at 650°C. Al thin film was pre-deposited on the substrate to provide the dopant of Al. Accordingly, the dopant of Al could diffuse from the Al layer to the ZnO nanowires. The ZnO:Al nanowires have therefore been synthesized. The growth mechanism of the nanowires was governed by vapor-liquid-solid (VLS). The characterization was using field emission scanning electron microscopy (FESEM), high resolution X-ray photoelectron spectrometer (HRXPS), thin film X-ray diffraction (TFXRD) and high resolution transmission emission microscopy (HRTEM). HRTEM image displayed that the ZnO:Al nanowires were grown along with the [0001] axis. In addition, TEM EDS mapping showed that the metallic Al was highly scattered and throughout in the ZnO nanowires. TEM/electron energy-loss spectroscopy (TEM/EELS) further confirmed that the dopant of Al has been incorporated into the ZnO nanowires. Cathodoluminescence (CL) and electric field emission analyzer was employed to investigate the optoelectronic properties of as-synthesized ZnO:Al nanowires. ¹R.-C. Wang, C.-P. Liu and J.-L. Huang, Appl. Phys. Letts. 88, 023111,2006. ²C.-L. Hsu, S.-J. Chang, H.-C. Hung, Y.-R. Lin, J. Electrochem. Soc., 152 G378 2005.
HP-7 Specific Details of Structure Formation of Ion-Beam Coatings of Cr-UDD, Cr-Al₂O₃ System M. Andreyev, A. Ilyuschenko, L. Markova (Powder Metallurgy Institute, Belarus) The interest to the nanomaterials and compositions on their base is determined by the possibility of significant modification or even change of surface properties of deposited parts in principle. The pure ion-beam Cr coatings as well as ion-beam Cr coatings with additions of 5% ultra-dispersed diamond (UDD), and 5% and 10% ultra-dispersed Al₂O₃ into the Cr targets for sputtering were selected as subject of investigation. The scanning electron microscopy in conjunction with mi-cro radio spectral analysis and atomic force microscopy were selected as basic methods of coatings morphology investigations. When determining coatings micro hardness the load on indenter was 0.02 N. It is shown in the paper that introduction of nanosized particles of UDD and aluminium oxide into the chromium targets for sputtering leads to the uniform distribution of elements upon sur-face and formation of homogeneous columnar structure of formatted coatings. It is determined that by increasing of UDD and Al₂O₃ quantity in the target for sputtering the grinding of coating structure and increasing of inhomogeneity of micro mechanical properties can be observed. It is shown that coatings have more homogeneous structure when sputtering on the warmed-up backing plate with subsequent cooling in vacuum. It is indicated that introduction of 10% Al₂O₃ into the target for sputtering increases micro hardness a little in comparison with 5% Al₂O₃ in the target for sputtering. It is determined that introduction of Al₂O₃ into the target for sputtering increases the value of coating micro hardness two times in comparison with coating of pure chromium (from 7600 MPa to 14000 MPa). In case of introduction of 1% UDD into the target for sputtering micro hardness of ion-beam coating will be increased up to 16500 MPa while introduction of 5% UDD will rise micro hardness up to 25900 MPa.
HP-8 Electromigration Back Stress Model on Electromigration Lifetime Prediction in Short Length Copper Interconnects Y.-L. Cheng (National Chi-Nan University, Taiwan) The short length on the electromigration lifetime is a useful effect to increase current limits in advanced circuits. A way to increase current limit is to consider the Blech effect. The electromigration threshold due to belch effect in copper interconnect for 65nm and 45nm technology is reported in this study. The critical product (jL)c was determined by varying the metal length and stress current density. A large (jL)c for 65nm technology was found. Finally, this critical product (jL)c as the accelerated EM length factor was used to predict the lifetime. It is shown that the lifetimes of short leads with less than 5 mm have at least 8.68 and 4.71 times higher than that of 250 mm metal lead.
HP-9 Formation of Ge Nanocrystals by Oxidizing SiGeN Thin Film C.-C. Lin (National Chiao Tung University, Taiwan); T.-C. Chang (National Sun Yat Sen University, Taiwan); P.-T. Liu, C.-H. Tu, C.W. Hu, H.-C. Liu, S.M. Sze, C.-Y. Chang, T.-Y. Tseng (National Chiao Tung University, Taiwan) The germanium nanocrystal formation by oxidizing silicon germanium nitride (SiGeN) thin film layer with distributed charge storage elements is proposed in this work. A large memory window is observed due to the formation of germanium nanocrystal in the metal-oxide-insulator-oxide-silicon (MOIOS) structure. The evident threshold voltage shift for nonvolatile memory device with the high-temperature oxidized SiGeN/a-Si stack layer is sufficient to define the signal "0" and "1". Also, the manufacture technology using the sequent high-temperature oxidation of amorphous silicon (a-Si) layer acting as the blocking oxide is proposed to enhance the performance of nonvolatile memory devices. By Transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) analysis, it was found that the longer duration of dry oxidation causes obvious Ge nanocrystals formation upon the tunnel oxide. In contrast with pure dry oxidation, using steam treatment after dry oxidation of SiGeN thin film further improves the quality of blocking oxide and reduces the thermal budget of fabrication process.
HP-10 Structure and Photoluminescence Properties of Strong Blue-Emitting Alumina Film Developed From Liquid Sol at Low Temperature C.-H. Peng (Ming Hsin Uinversity of Science and Technology, Taiwan); W.-L. Kuo, C.-S. Hsiao, S.Y. Chen (National Chiao Tung University, Taiwan) The optical properties of pure and doped nanostructures have received much attention because of their intrinsic characteristics and important applications. In this work, a clear sol was prepared by dropping aqueous NH₃ solution into aqueous Al(NO₃)₃·9H₂O solution, and then peptized with nitric acid. The alumina films were fabricated by spinning coating the clear sol on Si and glass substrates and thermally treated at 50-800°C. It was found that strong blue photoluminescence emission at ~440 nm could be observed and varied with pH value of peptization solution, annealing temperature and atmosphere. More surprising, an ultra-strong blue-emitting alumina film can be obtained at low temperature such as 50°C. It was believed that the strong photoluminescence is associated with defect centers which are related to phase transformation and chemical bond cleavage. Therefore, the phase evolution, microstructure and photoluminescence properties of the alumina film grown at low temperature will be discussed in this presentation.
HP-11 Minor Refractory-Metal Doping to Strengthen Ultrathin Electroless Co-Based Barriers Initialized by an Innovated Seeding Treatment C.S. Hsu (National Formosa University, Taiwan); S.T. Chen (Hsiuping Institute of Technology, Taiwan); Y.S. Tang, G.S. Chen (Feng Chia University, Taiwan) An electrochemical approach without involving activation-related processes is presented to grow metallic seeds of sizes only ~3 nm, subsequently initializing the deposition of thin films of Co-B and Co-W-B on thermally oxidized SiO₂ layer (100 nm) on Si using electroless plating. Thermal stability of the Co-based films as barrier layers for copper was evaluated by analyzing Si/SiO₂/barrier stacked samples using sheet resistance measurement, depth-profiling secondary ion mass spectroscopy, and scanning and transmission electron microscopy. According to these analyses, the Co-B binary barrier layers that have been annealed (450°C/1 h) are converted into Co₂Si facetted granules by the outgoing Si, and are insufficient to retard Cu diffusion. However, doping a minor amount (< 3 atom %) of tungsten not only strengthens the thermochemical and microstructure stability of the barrier layers, but also significantly reduces the self-diffusion of the matrix cobalt, hence alleviating intermixing of cobalt, copper, and silicon. The strengthening mechanism of the ternary barrier layer is clarified to be associated with a fundamental change in its microstructure.
HP-12 Evidence on the Carbon Facilitated Anatase to Rutile Phase Transformation for the Visible-Light Responsive Carbon Containing TiO₂ Nanoparticles S.B. Wu, J.B. Wang, S. Treschev, C.L. Cheng (National Dong Hwa University, Taiwan) Visible-light-responsive titanium dioxide (TiO₂) has attracted increasing attention recently. Commercially available TiO₂ responses only in the UV region; whereas visible-light-responsive TiO₂ allows using the visible region of the solar light for photocatalytic reactions. A new carbon containing visible-light-responsive mixed-phase TiO₂ has been proposed and proved to be efficient^[1]. Enhanced photocatalytic effects were found when anatase mixed with carbon covered rutile phases in the TiO₂ nanoparticles^[2]. In this study, we will discuss the formation mechanism on the mixed-phase TiO₂. The mixed phase was found due to carbon facilitated anatase to rutile phase transformation at lower temperature. Evidence on the carbon facilitated anatase to rutile phase transformation at lower temperature (200°C) was demonstrated through in-situ observation of Raman mapping on the transformation. The mechanism leading to the phase transformation will be discussed. ^[1] Yao-Hsuan Tseng, Chien-Sheng Kuo, Chia-Hung Huang, Yuan-Yao Li, Bo-Wen Chou, and Chia-Liang Cheng, M. - S. Wong, Visible-Light-Responsive nano-TiO₂ with mixed crystal lattice and its photocatalytic activity, Nanotechnology, 17, 2490-2497(2006). ^[2] P. - W. Chou, S. Treschev, P. - H. Chung, C. - L. Cheng , Y. - H. Tseng, Y. - J. Chen, M. S. Wong, Observation of carbon-containing nanostructured mixed titania phases for visible light photocatalysts, Appl. Phys. Lett. 89, 131919(2006).
HP-13 Spectroscopic Investigation on a Single CuO Nanowire C.Y. Huang, S.Y. Wu, M.H. Chou, C.L. Cheng (National Dong Hwa University, Taiwan) In this study, well separated CuO nanowires with ~30 nm in diameter and up to 50µm long are synthesied on cupper substrate using thermal oxidation method. We performed a spectroscopic investigateion on one single CuO nanowire. Confocal Raman spectra of a single CuO nanowire permit direct observation of the structural nature of an individual CuO nanowire as a function of the growth length from the substrate. Raman line width analysis revealed the growth boundary on one single nanowire. Short-circuit diffusion was accounted for the growth mechanism of the nanowires from the cupper substrate. Further analysis of the Raman A_g, B_g⁽¹⁾ and B_g⁽²⁾ Raman shifts revealed the phonon modes are quantum confined in the radial direction of the nanowire. The photoluminescence of a single CuO nanowire was also observed at room temperature using 488 nm wavelengths laser excitation at various positions on the nanowire from the substrate. The blue shift on the two observed luminescence peaks suggested these luminescence were subject to quantum effects. The origins of two observed luminescence peaks were discussed.
HP-15 Photoconversion Efficiency Enhancement of DSSC by W_xTi_yO_z Electrode Y.-C. Chen (National Chung Hsing University, Taiwan); K.-W. Weng (Mingdao University, Taiwan) Dye-sensitized solar cells (DSSCs) are low-cost solar cells to compare other solar cells on the marketing. These cells are extremely promising because they are made of low-cost materials and do not need elaborate apparatus to manufacture. They are composed by a semiconductor formed between a photo-sensitized anode and an electrolyte, a photoelectrochemical system. Additionally the charge separation is not provided solely by the semiconductor, but works in concert with a third element of the cell, an electrolyte in contact with both. Most of the small losses that do exist in DSSCs are due to conduction losses in the TiO₂ and the clear electrode, and the optical losses in the front electrode. Therefore, we focus on electrode to modify and try to instead of TiO₂ by W_xTi_yO_z. The dye is highly efficient in turning photons into electrons, it is only those electrons with enough energy to cross the TiO₂ bandgap that will result in current being produced. In this research, we used RF-sputter system and W-Ti alloy target to deposit oxide films to decrease bandgap and enhance photoconversion efficiency in DSSCs. The quantity contained and bonding energy was determined by Rutherford backscattering spectrometer (RBS) and X-ray photoelectron spectroscopy (XPS). At the crystalline phase and surface morphology of the specimen was identified by x-ray diffraction (XRD) and scan electron microscope (SEM) respectively. To find out that different composition of W and W_xTi_yO_z films affect on DSSC photoelectric effect.
HP-16 Photoluminescent Properties of Ce³⁺ ,Eu³⁺ Co-Doped Yttrium Aluminum Garnet Phosphors via Combustion Method H.H. Kwak, S.J. Kim, H.H. Yoon, K.H. Kim, H.W. Choi (Kyungwon University, Korea) For this study, Yttrium aluminum garnet (YAG) particles co-doped with Eu³⁺ and Ce³⁺ were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and photoluminescence (PL). Single-phase cubic YAG:Ce,Eu crystalline powder was obtained at 800°C by directly crystallizing it from amorphous materials, as determined by XRD techniques. There were no intermediate phases such as YAP (yttrium aluminum perovskite, YAlO₃) and YAM (yttrium aluminum monoclinic, Y₄Al₂O₉) observed in the sintering process. The SEM image showed that the resulting YAG:Ce,Eu powders had uniform sizes and good homogeneity. The grain size was about 50nm. The photoluminescence spectra of the YAG:Ce,Eu nanoparticles were investigated to determine the energy level of electron transition related to luminescence processes. It was composed a broad band of Ce³⁺ activator into the line peaks of Eu³⁺ in YAG host without the reduction of emission intensity. The PL intensity of Ce³⁺ has the wavelengths of 480-650 nm and The PL intensity of Eu³⁺ has main peak at 590nm.
HP-18 Growth of ZnO Films with Hexagonally-Packed Pores by the Cathodic Potentiostatic Electrochemical Deposition and Microsphere Lithography C.-J. Chang, S.-T. Hung (Feng Chia University, Taiwan) ZnO films with hexagonally-packed pores were fabricated on ITO glass substrates in large area by the cathodic potentiostatic electrochemical deposition and microsphere lithography method. This method includes self-assembled polymeric hollow particles as microsphere mask, growth of ZnO nanosheets (10 - 40nm thick) in the interstics, and removal of microsphere mask. The diameter of the hole depends on the size of the hollow microsphere. The hollow particles with only thin polymeric shells are used as the mask because they can be fixed by heating and removed by solvent immersion treatment. Hexagonally-packed holes with different diameters (400 nm and 900 nm) were formed by the growth-hindered ZnO nanosheets. The morphologies of the films depend on the zinc salt concentration and the cathodic potentiostatic electrochemical deposition parameters. Higher concentration leads to rougher morphology. Higher voltage and longer deposition period result in larger ZnO nanosheets and deteriorated patterns caused by the deformation of the microsphere mask. The ordered ZnO pore structure is expected to play an important role as building blocks for nanostructured ZnO - conjugated polymer solar cells by increasing the ZnO - conjugated polymer heterojunctions.
HP-19 Synthesis of Compound TiO₂ Coating for a Combined Solar Conversion and Self-Cleaning Application H.-C. Shih (National Tsing Hua University, Taiwan); C.-C. Yen, L.-S. Chang (National Chung Hsing University, Taiwan); D.-Y. Wang (Mingdao University, Taiwan) TiO₂, especially in anatase phase, exhibits the unique property of photo-catalysis under irradiation at UV wavelengths. Various applications such as disinfection, deodorizing, self-cleaning, water treatment, and etc. have been unveiled for commercialization. One of the most promising applications of the photo-catalytic TiO₂ thin film will be for the modern building materials. An investigation was conducted on the compound TiO₂ coatings with a combined solar conversion and self-cleaning effects for building-integrated photovoltaic (BIPV) for application. The band gap structure of the TiO₂ on ITO glass, served as photovoltaic solar cell was modified by metal plasma ion implantation (MPII) technique to increase the responding range of the incident light. Sequentially, the self-cleaning, photo-catalyst thin film were deployed by spraying metal-doped TiO₂ suspension on top of TiO₂ photovoltaic film. The transparency of the nanoscale, self-cleaning TiO₂ thin film will provide sufficient light transmittance for the solar conversion on the underlying MPII-improved TiO₂ solar cells. The metal-doped TiO₂ suspension possesses the properties of the super hydrophilicity and self-cleaning under visible light irradiation. The hydrophilicity behavior will be analyzed by the contact-angle measurement. The photon-to-current conversion efficiency (IPCE) and the decomposition rate in aqueous methylene blue solution will be carried out to verify the feasibility of this compound TiO₂ thin films for BIPV applications.
HP-20 Effects of Piezo-Electric ZnO Interlayer on UV-Transmission and Contact Resistance of ITO/ZnO/p-GaN Structure in Blue Light Emitting Diodes W. Kim, S.J. Yun, H.S. Uhm, J.S. Park (Hanyang University, Korea) GaN-based light emitting diodes (LEDs) have commercialized applications in green, blue and ultraviolet (UV) range of optical spectra. However, the ITO/p-GaN structure in GaN-LED devices cannot easily form a good ohmic contact due to a high resistance and a large work function of p-GaN, which may degrade the luminance and external quantum efficiency of the devices. In order to improve p-type ohmic contact, various interlayer (IL) materials between ITO and p-GaN have been investigated. However, the ohmic properties of ITO/IL/p-GaN sensitively depended on the crystal quality of the interlayer, which made it less reliable for the fabrication of high-performance LEDs. In this work, we suggest for the first time the use of piezo-electric ZnO interlayer in GaN blue LEDs for achieving high UV-transmittance and excellent ohmic contacts to p-GaN. Enhanced carrier injection rate in p-contacts is expected due to a large work function and a spontaneous electric dipole effect of thin ZnO layer. Thin films (~ 1 nm) of ZnO are deposited on p-GaN by RF reactive sputtering and annealed at 400-600°C for 1 min in air ambient to improve their crystal quality. ITO (~ 150 nm) films as a transparent conducting oxide (TCO) layer are deposited on ZnO by RF sputtering method. For all the contacts formed, junction morphology and contact resistance are analyzed using x-ray photoemission spectroscopy (XPS), field-emission SEM and transfer length method (TLM), in terms of the conditions used for ZnO/ITO contact formation. Furthermore, UV-transmittance and quantum efficiency of LEDs fabricated are characterized.
HP-21 Temperature-Dependent Memory Characteristics of SONOS-TFTs S.-C. Chen, T.-C. Chang (National Sun Yat Sen University, Taiwan); Y.-C. Wu (National Tsing-Hua University, Taiwan); J.-Y. Chin (National Sun Yat-Sen University, Taiwan) In this study, the temperature-dependent memory characteristics of SONOS-TFTs for nonvolatile memory application were investigated. As the device are programmed at high temperature, the hole injection through blocking oxide from gate and migration to tunneling oxide layer leads the threshold voltage decreasing as the programming time increases. In addition, the programming and erasing characteristics indicated the P/E efficiency was reduced as the temperature increasing. The retention characteristic of the device programmed at highest temperature exhibits the best charge storage ability. Because the charges captured in the shallow traps of nitride layer can easily de-trap as temperature rising, the memory characteristics are mainly dominated by charges stored in the deep traps at high temperature.
HP-22 Field Emission Properties of Ag/SiO₂/Carbon Nanotube Films by Pulsed Current Electrophoretic Deposition S.-C. Wang (Southern Taiwan University, ROC); B.-C. Huang (Southern Taiwan University, Taiwan); C.-Y. Chen (Feng Chia University); H.-M. Lin (Tatung University, Taiwan); C.-K. Lin (Feng Chia University, Taiwan) In this study, the microstructure and field emission properties of the Ag/SiO₂/carbon nanotube (CNT) films deposited by pulsed current and directed current were investigated. Multi-walled carbon nanotube was suspended in the mixture of isopropyl alcohol and ethanol with Ag and SiO₂ powders. Polyethyleneimine and Disperbyk-184 were used as dispersants and surface charger for the CNTs and the suspended particles. The CNT/Ag/SiO₂ film was prepared by electrochemical station using different waveform with pulsed or pulse-reversed current. The results showed that the surface morphology of the as-deposited film prepared by pulsed current exhibited more smooth than that prepared by directed current. While the uniformity of the thickness was also improbed by the pulsed-current deposition. The carbon nanotube deposited by the pulsed current tended to align uniaxially and parralelly to the electric field direction. The pulsed current controlled by applying 35 V for 1 s and -0.001 V for 1 ms has the optimum conditions for microstructure and field emission properties. The field emission measurement showed that the low turn-on field of 1.25 V/µm and threshold field of 2.5 V/µm. The light emission by a diode-type display consisting of a phosphor coated transparent-electrode showed that the phosphor luminescence image in 1 x 1 cm² has a strong, fine spot and uniform luminescence.
HP-23 Fabrication of Solar Cell with CdS-Sensitized TiO₂ Photoelectrode S. Biswas, M.F. Hossain, T. Takahashi (University of Toyama, Japan) Dye sensitized solar cells (DSCs), have been widely investigated as a next generation solar cell because of their simple structure and low manufacturing cost. The high light-to-energy conversion efficiencies achieved with dye sensitized solar cells may be attributed to the dye sensitized nano porous photo-electrode. One of the alternative methods to extend the light absorbing property of TiO₂ photoelectrode of DSCs and to enhance the overall efficiency of the DSCs is to couple TiO₂ with narrow band gap semiconductors which act as a sensitizer. Therefore, in this present study instead of dye CdS was used as a sensitizer to TiO₂ layer. The TiO₂ layer was deposited by reactive magnetron sputtering technique with various sputtering pressures and CdS was deposited by ammonia free chemical bath deposition (CBD) technique with sodium citrate as a complexing agent. The photo-conversion efficiency was calculated for all the solar cells with different TiO₂ layers. It has been observed that performance of the DSCs mainly depends on the structure and surface morphology of the TiO₂ layer. The structure and surface morphology of TiO₂ and CdS layer was investigated by atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). Incident photon-to-current efficiency (IPCE) was also calculated for all the solar cells.
HP-24 Electrical Conduction and TDDB Reliability Characterization for Low-k SiCO Dielectric in Cu Interconnects L.K.S. Chang-Liao (National Tsing Hua University, Taiwan) Leakage current and conduction mechanism of back-end-of-line (BEOL) dielectric using low-dielectric constant (low-k) carbon-doped silicon oxide (SiCO) are investigated in this work. Temperature-dependent leakage, Schottky emission and Poole-Frenkel emission of dense and porous low-k SiCO are respectively analyzed. Meanwhile, time-dependent dielectric breakdown (TDDB) study in low electrical field verifies a square root of electrical field behaviour for low-k SiCO lifetime prediction. Additionally, TDDB with regard to lifetime, failure mode, thermal activation energy and length scaling effect are also investigated. Finally, a TDDB characterization for dense and porous low-k SiCO is obtained for the reference of process improvement and risk assessment.
HP-25 Characterization, Electron Field Emission, and Gas Sensing Properties of Sb Doped SnO₂ Nanowires J.-M. Wu (Feng-Chia University, Taiwan) We demonstrate that the Sb doped SnO₂ nanowires can be synthesized by thermal evaporation at 900°C. Thin-film X-ray diffraction pattern showed that as-synthesized nanowires were a single phase of rutile structure. Field emission scanning microscopy image revealed that the nanowires were with diameters of 80-120 nm and lengths of up to several ten µm. High-resolution transmission electron microscopy (HRTEM) with X-ray energy dispersion spectrometer and electron energy loss spectroscopy (EELS) was used to demonstrate the element concentration mapping and the energy distribution of electrons. HRTEM image further confirmed that the crystallinity of the SnO₂ nanowires was accompanied with crystal defect and lattice distortion while the dopant of Sb was incorporate into the SnO₂ nanowires. The electron field emission and gas-sensing properties have also been investigated.
HP-26 Effect of Thin TiO₂ Passivation Layer on the Performance of Dye Sensitized Solar Cells M.F. Hossain, S. Biswas, T. Takahashi (University of Toyama, Japan) Dye sensitized solar cells (DSCs), have attracted great interest because of their potential application as a low cost alternative to conventional p-n junction solar cell devices. The high light-to-energy conversion efficiencies achieved with dye sensitized solar cells (DSCs) may be attributed to the photo-electrode. However, high porosity of sol-gel derived TiO₂ usually lead to leakage current between FTO substrate and the electrolyte. Reactive magnetron sputtering is a very promising technique for large-area uniform coating of TiO₂ thin film and it has potential to control the micro-structure through the process of modification of different sputtering parameters. In this present study to prevent leakage current a thin TiO₂ under-layer were deposited on FTO substrate by facing target reactive magnetron sputtering deposition technique with the sputtering pressure ranging from 0.1Pa to 2 Pa, 400⁰ C. The upper TiO₂ layer was deposited by conventional sol-gel technique with 1.0 g of polyethylene glycol (PEG). The photo-conversion efficiency was calculated for all the solar cells with different TiO₂ layer to evaluate the economic viability of this technique. It has been observed that performance of the DSCs is highly dependent on the structure and morphology of the TiO₂ under-layer.
HP-28 Improvement in Pitting Corrosion Resistance of the Al_xCrFe_1.5MnNi_0.5 High Entropy Alloys by Prior Anodic Treatment in Sulfuric Acid Solution C.P. Lee, Y.Y. Chen (National Tsing Hua University, Taiwan); M.W. Huang (National Chung Hsing University, Taiwan); J.W. Yeh, H.-C. Shih (National Tsing Hua University, Taiwan) High entropy alloys are newly developed family of multi-component alloys that consist of various major alloying elements, including copper, nickel, aluminum, cobalt, chromium, iron and others. Each element in the alloy system is present at between 5 and 35 atom %. High entropy alloys are totally different from the conventional alloys in crystal structures and physical properties. For example, (1) ease of amorphization and nanoprecipitation in the alloy, (2) thermal stability, (3) high hardness, and (4) superior corrosion resistance. The electrochemical impedance spectra (EIS) of the Al_xCrFe_1.5MnNi_0.5 (x=0, 0.3, 0.5) alloys, obtained in 0.1 M HCl solution, clearly indicated that the polarization resistance (R_p) increases as the concentration of aluminum increases, and they are significantly lower than that of the 304 stainless steel. Hence, the Al_xCrFe_1.5MnNi_0.5 alloys have been anodized in 15 % H₂SO₄ solution to optimize its surface structure and minimize the susceptibility to the pitting corrosion. Under constant voltage, the corresponding current drops with the anodizing time accounting for the establishment of the passivity resulting from the growth of the multi-major component alloy anodized film. The polarization resistance (R_p) increases in the EIS measurement by two orders of magnitude after anodized CrFe_1.5MnNi_0.5 and Al_0.3CrFe_1.5MnNi_0.5 alloys in sulfuric acid solution. Conversely, the polarization resistance decreases after anodized Al_0.5CrFe_1.5MnNi_0.5 alloy.
HP-29 Corrosion and Wear Behavior of TiAlN/ Pt Multilayers M. Flores (Universidad de Guadalajara, Mexico); L. Huerta (Universidad Nacional Autonoma de México, Mexico) The multilayers were deposited by reactive magnetron sputtering with the aim to improve the corrosion and wear resistance of metallic substrates. In this work we report the results of studies of the influence of the period size on the corrosion and the wear abrasion resistance of TiAlN/ Pt and TiALN/TiAL multilayers deposited on 316L stainless steel. The period size was from 20 nm to 1000nm. The wear was studied using a micro abrasion system as a function of the contact severity, the changes in the contact severity were achieved varying the abrasive particle size and the load applied. The corrosion was studied using open circuit potential measurements and potentiodinamyc polarizations in ringer solutions. X-Ray Diffraction analysis (XRD) was used to study the influence of the period size on the texture of multilayers. The composition of the films was determined by Rutherford Back Scattering (RBS) and X-Ray Photoelectron Spectroscopy (XPS) depth analysis. The XPS also determine oxidation species on the surface before and after corrosion tests. The results indicated that it was possible increasing the corrosion resistance when layers of Pt are deposited. It was found that for TiALN/TiAl multilayers the period size have a strong influence on the corrosion behavior.
HP-30 Diode Properties of Nanotube Mats B.T. Hicks (Brigham Young University, United States of America); S.A. Getty (NASA -- Goddard Space Flight Center); D.D. Allred (Brigham Young University) Making semiconductor devices based on single-walled carbon nanotubes (SWCNT) is one the more compelling, near-term potential applications of these long but ultrathin structures. We report seeing diode-like behavior across a random network of SWCNT contacted by asymmetric metal electrodes. Previously diodes have been reported only across well-aligned, non-networked SWCNTs.° Although no effort was made to align the SWCNTs in the mats which make up our test samples, or to eliminate metallic nanotubes, current rectification was observed in the source-drain bias range of -3V to +3V. This was somewhat surprising since, although in a random mixture of single-wall carbon nanotubes (SWCNT) metallic tubes are in the minority (~ 1/3); they could potential act as shunts masking the electric properties of the semiconducting majority. We have focused on and discuss the role of Al-to-Au electrode distance in rectification. Efforts to further characterize the electronic nature and optimize the diode response of the network devices have progressed. The lowest leakage current thus far measured is 5% of the current carrying capacities. Maximum forward-biased current capacities between 8 μA and 22 μäA have been observed with 136 kΩ to 375 kΩΩseries resistances, respectively. ¹Chenguang Lu, et al, Appl. Phys. Let., 88, 133501 (2006)}
HP-31 In-Situ Investigation of Corrosion Behaviors of CrN Thin Film by a Liquid Mode Atomic Force Microscope in Etching Solution Y.-C. Kuo (National Taiwan University of Science and Technology, Taiwan); J.-W. Lee (Tung Nan University, Taiwan); C.-J. Wang (National Taiwan University of Science and Technology, Taiwan) Liquid mode atomic force microscopy (LMAFM) has become a useful tool to in-situ study the surface morphologies and corrosion reactions of material in corrosive medium down to nano scale. In this study, the chromium nitride thin film has been deposited by a bipolar symmetric pulsed DC reactive magnetron sputtering system. In-situ corrosion images were observed on the coating surface immersed in a selective etching solution by the LMAFM. In this work, chemical etching process was performed on the CrN coating in a general corrosion form. The surface, cross-sectional morphologies and crystalline phases of coating before and after corrosion attack were examined with a field emission SEM and X-ray diffractometer, respectively. Scanning electron microscopy and energy dispersive spectrometer (EDS) were conducted to explore the chemical composition variations around corrosion pits. It is observed that the etching solution attacked the coating through the interfaces of columnar structures. The CrN thin film was corroded to form uniform pits on nano/micro scale throughout the coating. The surface roughness of thin film thus increased from 7.3 nm to 30.9 nm after etching reaction.
HP-32 Synthesis and Properties of Vanadium Pentoxide One Dimension Nanostructure by Chemical Vapor Deposition Y.-C. Su (National Tsing Hua University, Taiwan); H.C. Shih (Chinese Culture University, Taiwan) Most vanadium pentoxide nanowires or nanorods were synthesized successfully by hydrothermal method in the past. Here we synthesized vanadium pentoxide nanorods with rectangular cross by chemical vapor deposition in the horizontal tube furnace. The diameter of nanorods were about 100nm and length from 1 to 10µmm The synthesis temperature was at 1000°and 1.5Torr from pure vanadium powder (V, 99.5% ). We used scanning electron microscopy (SEM) and transmission electron microscopy(TEM) to observe the morphology of nanorods. And use energy dispersive X-ray spectrum to analyze the composition of the nanorods. We also investigated its Raman spectrum and cathodoluminescence properties.
HP-36 Investigation of De-Plating Behavior of Pt Contact Pins in Semiconductor Cu Electroplating Process S.-Y. Hu, H.-S. Lee (National Cheng Kung University, Taiwan); K.-W. Chen (Taiwan Semiconductor Manufacturing Company Ltd., Taiwan); C.-C. Hung (National Cheng Kung University, Taiwan); S.-C. Chang, Y.-L. Wang (Taiwan Semiconductor Manufacturing Company Ltd., Taiwan) In semiconductor copper (Cu) metallization processes, electroplating process is used to produce (dual) damascene Cu lines due to its excellent gap-filling capability and high throughput. In the Cu electroplating process, circular platinum (Pt) contact pins are used to conduct the wafer edge during electroplating process, hence, these contact pins and wafer would be electroplated Cu films in the meantime. In addition, keeping the conductivity and surface smooth of Pt, the contact pins should be de-plated to remove coating Cu films after electroplating process. However, the potential of de-plating process causes the electrolytes occurring electrolysis reaction to generate bubbles and these bubbles will affect the yield on Cu defects due to their adsorptions on the wafer surface. In this study, electrochemistry analysis system is investigated to character the behavior of Pt de-plating process. According to the result, it is observed that electrolysis would not happen without bare Pt surface due the reduction potential difference between Cu and hydroxyl. The electric field distribution caused by the electrode resistance scale the effective area down for higher applied voltage during the de-plating process. Depend on these result, the most efficient bubble-less de-plating parameters could be easily constructed.

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