Papers

ICMCTF2008 Session CP: Symposium C Poster Session

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

Thursday Afternoon

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

CP-1 Surface Potential Pumping for High Frequency Capacitance-Voltage of MOS Capacitor Under Optical Illumination F.-Y. Jian, A.-K. Chu (National Sun Yat Sen University, Taiwan); M.-L. Liao (Air Force Institute of Technology, Taiwan); C.-M. Chang (UMC (United Microelectronic Corporation), Taiwan); T.-C. Chang (National Sun Yat Sen University, Taiwan) Under optical illumination, high frequency capacitance-voltage (C-V) of MOS capacitor has been investigated. The surface potential pumping model has been proposed and used to obtain the photo-capacitance formula. The simulation results are in good agreement with experiment data. This results imply that the photo-capacitance of MOS is not only dependent on the generation lifetime of minority carriers and surface potential (both decrease according to light intensity increasing theoretically) at silicon side, but also the minority carriers at silicon side pumped by surface potential variation with small-signal voltage is necessary to be considered. Thus, the proposed model could be used to clear the optical illumination mechanisms for MOS Capacitor.
CP-2 Synthesis of ITO Thin Films on Polymer Substrate Using In-Line Sputtering System Y.S. Jung, K.H. Kim (Kyungwon University, Korea); M.J. Keum, J.G. Han (Sungkyunkwan University, Korea) Flexible Organic light-emitting diodes (FOLED) device have been widely investigated for their potential applications in high efficiency, low drive voltage, large area and full color flat panel displays. In this study, the Indium tin oxide (ITO) thin films for use as a transparent electrode in flexible organic light-emitting diodes (FOLEDs) were prepared on polymer substrate with barrier layer such as SiO_x by In-line sputtering system. The electrical, optical, structural characteristics of ITO thin films were evaluated by Hall Effect Measurement (EGK), four-point probe, X-Ray Diffractormeter (Rigaku), UV/VIS spectrometer with a spectral range of 300-1100nm, scanning electron microscopy (SEM) and atomic force microscope (AFM).
CP-3 Hard Transparent Conducting Doped Titania Oxide Films K.H. Hung, Y.J. Tsai, P.W. Chou, T.K. Chen, M.S. Wong (National Dong Hwa University, Taiwan) Titania is a wide bandgap semiconductor and is a photocatalyst under UV light. If properly doped, titania can work photocatalytically under visible light. It has recently been reported that Nb-doped anataseTiO₂ (Ti_1-xNb_xO₂) is an excellent transparent conducting oxide (TCO) with electrical resistivity of 2.1 x 10-4 Ocm, and internal transmittance 95% in the visible region. These values are comparable to those of typical TCOs such as indium tin oxide (ITO) and aluminum doped zinc oxide (AZO). We have produced/investigated various visible-light activated doped-titania films and started to measure their mechanical and electrical properties. The dopants in titania include anions like N, C and B and cations like V, Cr and W. The results show that the doped titania films possess high visible-light transparency as well as enhanced hardness and conductivity. For example, carbon doped titania films have over 90% transmittance in visible light region, high hardness up to 17.3 GPa and reduced resistivity of 0.1 O.cm.
CP-4 Transparent Conductive Properties of Sputtered ZnO Thin Films S.-N. Bai (Chienkuo Technology University, Taiwan); T.-Y. Tseng (National Chiao Tung University, Taiwan) This study describes the effect of substrate temperature on the structural and optical properties of rf magnetron sputtered alumina-doped zinc oxide (AZO) thin films. The AZO films were deposited on (001) oriented silicon substrate from a ZnO target mixed with alumina of 2 wt.% and an rf power of 80W at room temperature. The experiment shows that the growth of AZO films is strongly dependent on the substrate temperature. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements demonstrate that all the AZO thin films, except the films grown at 350°C, are single crystals with a wurtzite structure and present a preferred orientation along the (002) direction. The intensity of (002) peak is found to increase with increasing substrate temperature until a maximum, which located at 150°C, is obtained. After the maximum point, the intensity of (002) peak decreases as the substrate temperature increases continuously. It is suggested the ZnO film structure changed from crystalline phase to amorphous one with increasing substrate temperature. The electrical properties of the ZnO thin films are obviously affected by the substrate temperature. It is shown that the electrical resistivity increases with increasing substrate temperature at a range from 30 to 350°C. Optical transmittance measurements demonstrate that AZO thin films are highly transparent (> 85%); the energy bandgap in the crystalline films grown at lower substrate temperature is around 3.4eV, whereas the optical bandgap in amorphous films prepared at higher substrate temperature is larger than this value.
CP-5 Carbon Nanotube Incorporated Direct-Patternable SnO₂ Thin Film Formed by Photochemical Metal-Organic Deposition H. Kim, H.-H. Park (Yonsei University, Korea); H. Jeon (Hanyang University, Korea); H.J. Chang (Dankook University, Korea) Tin dioxide (SnO₂) has attracted attentions as a transparent conducting oxide of solar cell and transparent devices. However for applying to electrical devices, an improvement in the electrical property of SnO₂ thin film has been absolutely required. Furthermore during patterning by lithographic process using photoresist, thin films receive surface damages and degradation of properties. Recently, the hybridization with carbon nanotube has been widely investigated. Carbon nanotube is relatively chemically inert, exhibit excellent electrical and thermal conductivity, and show nonlinear optical properties and superior mechanical strength. In this work, carbon nanotubes were incorporated into SnO₂ thin films to improve the electrical property of the film and direct patterning of the films was carried out through photochemical metal-organic deposition using photosensitive precursors without photoresist and dry etching. For direct-patterning of film, wet and spin-coated films were simply exposed to UV through shadow mask. X-ray diffraction was served to provide the information of crystalline structure. The electrical and optical properties were investigated by using four-point probe and UV-VIS-NIR spectrophotometer, respectively. X-ray photoelectron spectroscopy was used for the surface chemical bonding state of film.
CP-6 Properties of Tn Doped Indium Oxide Films Prepared on Flexible Substrates Using a Dual Magnetron Sputtering System D.-G. Kim, S-.H. Lee, J.-K. Kim, J.-W. Kang (Korea Institute of Materials Science (KIMS), Korea) In order to realize the flexible devices, transparent conducting oxide (TCO) films should be prepared at relatively low temperature on flexible substrates such as polyethylene terephthalate (PET) film. ITO films were deposited on plastic films by a dual magnetron sputtering (DMS) method without intentionally heating substrates. The samples prepared by DMS system were compared with the sample deposited by a conventional DC magnetron sputtering method. We have investigated the electrical, optical, and mechanical properties of the samples by using Four-Point Probe, Hall Effect Measurement, UV-Vis-NIR Spectrophotometer, XRD analysis. Hall effect measurements and structural analysis explain the enhancement of electrical and optical properties.
CP-7 Characteristics of Amorphous Indium Zinc Oxide Thin Films Grown on Flexible Substrates at Room Temperature Y.S. Rim, S.M. Kim, H.H. Yoon, H.W. Choi, K.H. Kim (Kyungwon University, Korea) The amorphous indium zinc oxide (IZO) thin films were deposited on polyethersulfone (PES) and glass substrates by facing targets sputtering (FTS) system using an oxide ceramic IZO target (90 wt.% In₂O₃ and 10 wt.% ZnO). FTS system which consists of facing the two targets and the substrate loader located apart from the center of facing the two targets. So the energetic particles are restricted by magnetic force within plasma. Therefore the FTS system contributes to suppression of high energy particles bombardment to the substrate. In the results the FTS system can deposit high quality thin films at low temperature. The influence of sputter power, film thickness and gas flow rate on electrical and optical properties of IZO thin films deposited on transparent substrates (PES and glass), was studied. The electrical, optical, structural characteristics of IZO thin films were evaluated by Hall Effect Measurement, four-point probe, X-Ray Diffractormeter, UV/VIS spectrometer in visible range, scanning electron microscopy, respectively. As a result, we could prepare the amorphous IZO thin films with the resistivity of under 10^-4 [Ω-cm] and the optical transmittance of over 80% on PES and glass substrates.
CP-8 Properties of Inert Gas RF Plasma-Treated ITO Deposited by Pulsed Magnetron Sputtering A.N. Reed (Wright State University/Air Force Research Laboratory/RXBT / University of Dayton); J.G. Jones (Air Force Research Laboratory (AFRL/RXBT)); C. Muratore (Air Force Research Laboratory (AFRL/RXBT)/UTC, Inc.); A.R. Waite (Air Force Research Laboratory(AFRL/RXBT)/University of Dayton/UTC, Inc.); D.T. Petkie (Wright State University) Crystalline indium tin oxide (ITO) is optically transparent and electrically conductive, however, processing temperatures of >300°C are often required to obtain films with these useful properties, prohibiting deposition on polymer substrates. In the current work, the effects of pulse parameters in mid-frequency pulsed dc on as-deposited film composition and structure were investigated, as well as a post-depostion RF plasma treatment process designed to promote crystallization of the films on polymer substrates from ion bombardment. Raman spectroscopy and X-ray diffraction were used to show that the degree of film crystallization was dependent on the frequency and duty factor of the pulsed power supply used for deposition, as well as the parameters selected for the post-deposition RF plasma treatment. XPS was used to determine dependence of the processing parameters on the chemical composition of the ITO films. Models to describe how the pulsed power supply parameters and post-deposition plasma treatment enhanced crystallization and affected opto-electronic properties of the films will be presented.
CP-9 Synthesis and Characterization of ZnO and ZnO:Al Nanocrystalline Films Obtained by the Sol-Gel Dip-Coating Process C.D. Bojorge (REPSOL-YPF, CITEFA, CINSO, Argentina); E. Broitman (Carnegie Mellon University); H.R. Cánepa (Conicet, Citefa, Argentina); J.A. Badán, E.A. Dalchiele, R.E. Marotti (Universidad de la República, Uruguay); J.B. Miller, A.J. Gellman (Carnegie Mellon University) Nanocristalline zinc oxide films have been obtained by the sol-gel process. The films were deposited from precursor solutions by dip-coating on quartz substrates, and subsequently transformed into nanocrystalline pure or aluminium-doped ZnO films after a thermal treatment. The film microstructure and composition characterization was studied by AES, UPS, and X-ray diffraction. The optical properties were studied by transmittance spectroscopy. The adsorption energy of oxygen and CO was measured by Temperature Program Desorption (TPD) in the range 90-700 K. The nanocrystallite size, estimated by the Scherrer equation, resulted 8-20 nm. The optical transmittance of the ZnO layer in the visible region is rather high: about 90% for undoped samples and between 84 and 90% for the Al doped ones at 600 nm. In the UV region there is an absorption edge close to the accepted value of bulk bandgap energy for ZnO. The determination of this energy is 3.27 eV for undoped samples and 3.30 eV for the Al doped ones. The increase in bandgap energy in Al doped samples may be justified by band-filling effects. Close to 300 nm the transmittance diminishes in comparison to the visible value but still remains higher than 50% in all cases, because the samples have a nanometric thickness between 20 to 30 nm. The band edge absorption coefficient increases monotonically for the Al-doped samples but has a small peak for the undoped ones, which may be assigned to room temperature excitonic absorption. Valence band shifts due to butanol adsorption at room temperature was observed by UPS and compared to measurements on a (0001) ZnO single crystal surface.
CP-10 Ellipsometer Analysis in the n-k Plane for Unknown Substrates F.K. Urban, D. Barton (Florida International University) Ellipsometry is an optical analytical method based on measuring the change in polarization state of reflected or transmitted polarized light. A major challenge of the method has been the computation of reflecting surface physical parameters of interest from the raw measured data. The authors have developed methods using theorems of Complex Analysis to treat the cases of metal, semiconductor, and insulator films growing on known substrates, also of metals, semiconductors, and insulators. The work presented here explores this advanced treatment for films growing on unknown substrates. In one case we consider unknown homogeneous isotropic substrates. And in the second case we treat unknown substrates composed of unspecified layers of homogeneous isotropic films on a substrate. Advanced visualization methods will be presented using a specialized graphical user interface. Results for computed and for actual film data will be presented. The new computational method does not require initial estimates and eliminates the multiple solution problems inherent in least squares methods.
CP-11 Influences of Silicon Nano-Crystallized Structure on the Optical Performance of Silicon Oxynitride Rib Type Waveguide W.-J. Liu (I-Shou University, Taiwan); P.-H. Lee, C.M. Chen, Y.-C. Lai (National Cheng-Kung University, Taiwan); M.-H. Weng (National Nano Device Laboratories, Taiwan) Silicon oxynitride (SiO_xN_y) grown by plasma enhanced chemical vapor deposition (PECVD) is well-suited for the realized application of high contrast waveguides for the range of the refractive index can be largely tuned (1.45-2.0), and the waveguides based on the usage of SiO_xN_y core and silicon oxide cladding layers can be fabricated using conventional VLSI fabrication techniques. SiO_xN_y rib-type straight waveguides with 3% refractive index difference and the transmission spectrum of self-developed novel array waveguide gratings (AWG’s) device indicated the insertion loss, crosstalk and side-lobe were lower than -3 dB, -15 dB and -40 dB, respectively, by 3D beam propagation method were investigated in this study. The chip size of the whole AWG device is smaller than 4 cm x 1.5 cm, and the highest coupling loss of the rib waveguide for single mode fiber was about -1.6 dB. Based on the simulation results, the device can be really and easily fabricated by thin-film deposition, photolithography and dry-etching processes. The structures and compositions of the SiOxNy films were identified by x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS), respectively. High resolution transmission electron microscopy (HRTEM/EDAX) was used to study the localized interface structure and compositional distribution of SiO_xN_y films. The topography of SiOxNy films and rib structure waveguides were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optical characteristics of SiO_xN_y films and AWG device were measured by spectrophotometer.
CP-12 Effect of Annealing Processing on Physical Characteristics of Nanostructured Indium-Tin-Oxide Films by Sputtering H.S. Koo, C.-C. Peng, W.-C. Shih (Minghsin University of Science and Technology, Taiwan) Transparent conductive oxides for nanostructured indium-tin-oxide films on non-alkaline glass substrates have been fabricated using dc sputtering technique. The influence of thermal annealing processing on physical characteristics of transparent conductive oxide films have also been investigated and demonstrated. The physical properties of as-sputtered and as-annealed films were characterized by XRD, resistivity, light transmittance, AFM-based microstructure and surface analysis. With the increase of annealing temperatures, resistivity and light transmittance have some variations and improvements. The as-sputtered samples were treated in air atmosphere and resulted in oxygen-deficient oxide films, indicating the surface resistivity of oxide films decrease with increase of annealing temperatures. The average resistivity and transmittance of as-sputtered films are 1.623x10^-2 ohm-cm and 89.917%, while average resistivity of annealed films at 500°C for 2hrs is 6.393x10^-3 ohm-cm. Transmittance of annealed films at 450°C for 30mins is 91.252%. Grain size of as-sputtered and annealed films at different temperatures is observed by atomic force microscope and calculate activation energy(Ea) by Arrhenius equation, ? = A?exp-(Ea/RT).
CP-13 Development of ZnO Based Single and Multilayer Transparent Conductive Coatings D.R Sahu, J.-L. Huang (National Cheng Kung University, Taiwan) Transparent conducting coatings paid much attention due to their potential applications in opto-electronics, flat panel displays, solar cells etc. This field aims to develop highly conductive and transparent film to enhance device performance at room temperature. In order to improve the properties of transparent conductive films we have developed a range of single and multilayer coatings consisting of three to five alternating layers of ZnO and metals. We have used physical vapor deposition to prepare optimized coatings with excellent optical and electrical properties, improved thermal and long term stability. Optimum thickness of metal and ZnO layers were determined for high optical transmittance and good electrical conductivity. Several analytical tools such as X-ray diffraction, spectrophotometer, atomic force microscopy, scanning electron microscopy and four point probe were used to explore the possible changes in electrical and optical properties. Comparative studies on the properties of different transparent conducting coatings are performed. Multilayer coatings consisting of Al-doped ZnO and Ag metal show satisfactory properties of low resistance of 5 Ω/sq, high transmittance of 90 % and thermal stability up to 500⁰C. The electrical and optical properties of the multilayer were changed mainly by Ag film properties, which are also effected by the deposition process of the upper layer. Details of the preparation process and possible causes of changes in properties will be discussed during presentation.
CP-14 Electronic and Optical Properties of Nano-Crystalize TiO₂ Thin Film After Metal Ion Implantation Y.-N. Shieh, Y.-Y. Chang, C.-J. Su, D.-Y. Wang (Mingdao University, Taiwan) Metal plasma ion implantation has being successfully developed for improving the electronic and optical properties of semiconductor materials. In this study, the nano-crystalline of TiO₂ particles were synthesized by a duplex treatment of dip-coating technique and microwave process. Transition metal ions, such as Fe⁺ and Co⁺, and noble metal ions, such as Ag⁺, were implanted into the nanocrystalline TiO₂ thin film. The ion energy of metal ions was set at 40 keV with implantation doses of 1 x 10¹⁵-1 x 10¹⁶ ions/cm². After implantation, samples were carried out of annealing procedures at different temperature to investigate the change of microstructure and recovery of defects. In this study, field emission scanning electron microscope, transmission electron microscope, atomic force microscopy and X-ray diffraction using Bragg-Brentano and glancing angle parallel beam geometries were used to characterize the microstructure of the ion-implanted and annealed TiO₂ films. The composition and chemical bonding of ion-implanted TiO₂ films were evaluated by X-ray photoelectron spectrometry (XPS). The optical absorption spectra of the ion-implanted films were measured using a UV-visible spectrophotometer. The optical characterization showed the shift in optical absorption wavelength at infrared ray side, which was correlated with the structure variation of the metal-ion implanted nanocrystalline TiO₂.
CP-15 Study of the Luminescent Emission in Silicon Based Multilayer Systems Grown by PECVD Technique M. Ribeiro, I. Pereyra (University of São Paulo, Brazil) In order to study the influence of quantum confinement effects and interface phenomena in the luminescent properties of silicon based nanostructured films exhibiting luminescent emission in the visible region of the spectrum [1, 2], two types of silicon multilayer stacks were produced by PECVD technique: a-Si/SiO₂ stack and a-Si/SiN_x stack. This configuration is based on sequential arrangement of quantum wells with interfacial potential barriers. It is observed that the peak emission is tunable by the amorphous silicon layer thickness. The a-Si/SiN_x stack shows the major luminescent intensity attributed to the reduced band gap offset that permits major electron injection. The multilayers were characterized by: Raman scattering, Fourier Transform Infrared spectroscopy (FTIR), X-ray absorption near edge spectroscopy (XANES), photoluminescence (PL) and transmission electron microscopy (TEM). The results show that in both multilayers as deposited the silicon layer is amorphous and after heat treatment at temperature of 1000^oC crystallization of the silicon layer occurs observed by Raman, TEM and XANES. At this stage no luminescent emission was observed indicating the absence of confinement effects in the silicon wells.
CP-16 To Suppress Photo Leakage Current of Low Temperature Polysilicon TFT H.Y. Lu (National Chiao Tung University, Taiwan); T.-C. Chang (National Sun Yat Sen University, Taiwan); P.-T. Liu (National Chiao Tung University, Taiwan); C.W. Hu (AU Optronics Corporation, Taiwan); S. Chi (National Chiao Tung University, Taiwan) The market for liquid crystal displays has been rapidly expanding in recent years. The demand for a high luminance and a high contrast ratio in liquid crystal displays (LCDs), such as small-medium LCDs for projection device, mobile displays and displays for cars, is continuing to grow and seems insatiable. However, high luminance would increase photo leakage current (PLC) in the TFTs, which diminishes the voltages that are held across the pixel electrodes or affect the gray level controlling, which in turn, would cause a low contrast ratio and error color display. It is suffer the On/Off ratio of device and will affect the TFTs operating. In this work, we propose two methods to suppress the PLC. First scheme is to generate a plenty of trap states between the buffer layer and poly-Si active layer by O2 plasma treatment. Therefore, the electron-hole pairs excited by back light in the bottom of poly-Si layer would be recombined via the induced surface state. The PLC of poly-Si TFT with O2 plasma treatment on the buffer layer is decreased significantly. The second one is using light-shielding structure, here we employ the opaque material to shield the light, and it is the most effective to cut-off the light from the backlight source. Without additional masks, the light-shielding layer, buffer layer and active island are patterned by the same masks. The photo leakage current and the variation of sub-threshold swing in the proposed devices are suppressed completely. Furthermore, the electrical characteristics of proposed poly-Si TFTs with above mentioned methods are described and discussed in this paper.
CP-17 Effect of Various Metal Nanoparticles on the Poly(p-phenylene vinylene)(PPV) Precursor C.Y. Lee, S. Yoon, H.-H. Park (Yonsei University, Korea) Conjugated polymers can serve as the active material in polymer electroluminescent devices. The incorporation of nano-particles in conjugated polymer and the formation of nano-composite have been increasingly studied because of the enhanced optical electronic properties starting from the characteristics of organic light-emitting diodes(OLEDs) such as high luminescence, low drive voltage, and a variety of emission color. But our understanding of the effects of nanoparticles on the performance of organic devices is far from a complete. Merely, it has been known that the presence of nanoparticle can lead to enhancement of the performance. The performance of an OLED is strongly affected not only by the properties of its constituent organic layers but also by the electrodes and the interfaces they form with the carrier-transport layers. In this study, we made poly(p-phenylene vinylene)(PPV) nanohybrid films by the incorporation of various metal nanoparticles into the conjugated polymer PPV. We focused whether there is a change in the interaction between metal nanoparticles and matrix or not. We were also investigated the interaction between active nano-composite layer and metal cathode. The optical properties were investigated by using UV-Vis spectroscopy and photoluminescence measurements. The chemical bonding and electrical current characteristics of PPV nano-composite films were also investigated by X-ray photoelectron spectroscopy and I-V measurement, respectively.
CP-18 Effect of Sputtering Power on the Photocatalytic Activity of Facing Target Sputter Deposited TiO₂ Thin Films M.F. Hossain, S. Biswas (University of Toyama, Japan); K. Takahashi (University of Tokyo Hospital, Japan); T. Takahashi (University of Toyama, Japan); Y. Kubota (University of Yokohama City, Japan); A. Fujishima (Kanagawa Academy of Science and Technology, Japan) In recent years, titanium dioxide (TiO₂) with photocatalytic characteristics has received a great deal of attention because of its ability to detoxify environmental pollutants. Reactive sputtering is a very promising technique for large-area uniform coating of TiO₂ photocatalyst and it has potential to control the crystallographic structure and micro-structure through the process of modification of different sputtering parameters. Moreover, facing target reactive sputtering (FTS) provides better crystallinity and defect-free structure by total plasma confinement. In this present study TiO₂ thin films were deposited by facing target reactive magnetron sputtering on glass substrate with different sputtering power ranging from 200 W to 600 W. Interestingly it has been observed that all the properties of the TiO₂ thin films, including crystallinity, surface morphology and light absorption capability which regulate photocatalytic activity are largely influenced by the sputtering power The optimization condition for the maximum photocatalytic activity was revealed. The variation of photocatalytic activity with different sputtering power is interpreted in terms of different O₂ stoichiometry, crystallinity and surface morphology. The efficiency of the TiO₂ catalysis was studied to evaluate the economic viability of this technique.
CP-19 The Driving Performance of Organic Light Emitting Diodes With Ba/Al Cathode and the Effect of Ba Thickness by Measuring Built-In Potential J.T. Lim, G.Y. Yeom (Sungkyunkwan University, Korea) Built-in voltage for organic light-emitting diodes with Ba/Al cathode was studied using modulated photocurrent technique at ambient conditions. A built-in voltage of the device can be determined from the bias voltage-dependent photocurrent. The applied bias voltage when the magnitude of modulated photocurrent is zero corresponds to a built-in voltage. In actuality, built-in voltage in the device is occurred from a difference of work function between the anode and cathode. To measure a built-in voltage, the device which have a structure of ITO / Alq3 (150 nm)/ Ba (x nm, x =3, 2, 1 and 0) / Al (100 nm) was fabricated. The device adding Ba into cathode showed high built-in voltage, compared the Al-only device. This results in the lowering for barrier height for electron injection from the Alq3 / Ba interface to Alq3. For the device which have ITO / Alq3 (100 nm) / Ba (3 nm) / Al (100 nm), barrier height for electron injection showed a low value as 0.1 eV. On base of built-in voltage data, the device which has a ITO / 2-TNATA (30 nm) / NPB (18 nm) / Alq3 (62 nm) / Ba (3 nm)/Al (100 nm) structure showed the highest luminance of 54,000 cd/m2 and the highest efficiency of 2.6 lm/W, when compared with other devices having thickness of Ba between 0 and 2 nm.
CP-21 OLED Based on Novel Rare-Earth Tetrakis(β-diketone) Molecular Complexes W.G. Quirino, C. Legnani (Inmetro - National Institute of Metrology, Standardization and Industrial Quality, Brazil); M. Cremona, R.M.B. Santos (PUC-Rio, Brazil); M.A. Guedes, H.F. Brito (IQ- USP - University of São Paulo, Brazil); K.C. Teixeira (PUC-Rio, Brazil) Rare earth complexes with β-diketone ligands show intense photoluminescence resulting from the intramolecular f-f transition of RE ions after the harvesting of both singlet and triplet excitons produced on the surrounding ligands. RE ions have the spectroscopic characteristics to emit light in narrow lines, which makes the complexes with organic ligands candidates for OLED application. The RE³⁺ complexes are generally based on the neutral Lewis base adducts which has three β-diketonate ligands for each RE ion and they can be represented by the general formula [RE(β-diketonate)₃]. It is also possible to arrange four β-diketonate ligands around a single RE ion and in this way tetrakis(β-diketonates) complexes with the general formula [RE(β-diketonate)₄]^- are formed. Increasing the number of the β-diketonate ligands it is expected an improvement on light absorption and consequently an increase of the luminescence of RE ions through the antenna effect. In this work, we report the synthesis and the electro- and photoluminescence investigation of a novel RE tetrakis β-diketone complexes, such as M[Eu(tta)4] and M[Tb(acac)4], where M=Li⁺, Na⁺ and K⁺. The complexes were used to fabricate OLED devices. Thin films of MTCD (NPB) as hole transporting layer, tetrakis complex as active and electron transporting layer and aluminum as cathode were deposited sequentially by thermo evaporation onto ITO-coated glass substrates in a high vacuum environment system. OLED electroluminescence spectra show narrow emission peaks arising from the f-f transitions of the Eu³⁺ and Tb³⁺ ions.
CP-22 Synthesis of Silicon Oxide Barrier Thin Film Using Pulsed Magnetron Sputtering on Pre-Treated Polymer Substrates by ICP T.J. Byun, K.S. Shin (Sungkyunkwan University, Korea); Y. Setsuhara (Osaka University, Japan); J.G. Han (Sungkyunkwan University, Korea) Flexible organic light emitting diodes (FOLEDs) display using the polymer substrates has became the key issue in the display industry. But the polymer substrates have a drawback that they can not provide the long lifetime for flexible display devices, because the polymer substrates can not sufficiently provide the protection from the water vapor and the oxygen gas permeation. And due to polymer’s low surface energy, normally poor chemical reactivity, polymer surfaces offer poor adhesion to other contiguous materials. So to overcome polymer’s weak points, the plastic substrates used the flexible display device require the barrier layers and surface treatment. The barrier films have included the oxides of Na, Si, Mg, Al, Zr, Ti, and Ta. In particular, the silicon oxide film on polymer substrate has application to optical coatings, barrier coatings, and so on. Modification of polymer substrate by inductively coupled plasma (ICP) treatment has an advantage that low temperature process and easily control of polymer surface energy are possible. Therefore, in this study, we synthesized the silicon oxide barrier thin films on polyethylene terephthalate (PET), poly carbonate (PC) which is pre-treated by ICP in in-line magnetron sputtering system. The silicon oxide thin films were prepared by changing the oxygen gas flow and power density. To analyze the characteristics, we employed atomic force microscopy (AFM), scanning electron microscope (SEM), bending test, optical microscope, and the measure of WVTR using MOCON system.
CP-23 Manganese Activated Photoluminescence and Alternating Current Electroluminescence of Zinc Gallate Thin Films J.H. Heo, J.H. Kim (Chungbuk National University, Korea) Manganese activated photoluminescence (PL) and alternating current electroluminescence (EL) of zinc gallate (ZnGa₂O₄:Mn) thin films have been investigated. The ZnGa₂O₄:Mn films were prepared by radio frequency planar magnetron sputtering from a 2 mol% Mn-doped ZnGa₂O₄ target in an oxygen-argon mixture atmosphere. PL emission peaked at around 506 nm was observed from the ZnGa₂O₄:Mn target sintered at 1000°C for 5 hours and the films annealed at 800 ^oC for 3 hours in air. PL excitation spectrum of the annealed ZnGa₂O₄:Mn films was peaked at 294 nm. The half-stack alternating current thin film electroluminescent (ACTFEL) devices were constructed using an inverted single-insulating layer structure, indium tin oxide (ITO)/ZnGa₂O₄:Mn/barium titanate (BaTiO₃)/Al. The fabricated devices were tested using a bipolar trapezoidal drive waveform with the drive frequency of 2.5 kHz. The emission peak of EL was at ~508 nm, and the EL spectra were identical to the PL spectra. The color coordinates of the EL emission were x=0.11 and y=0.7, giving an indication of good CIE chromaticity coordinates for green phosphor.
CP-24 Raman Inspection for the Annealing Induced Evolution of sp² and sp³ Bonding Behavior in Sandwiched Si/C/Si Multilayers C.K. Chung, C.W. Lai, C.C. Peng, B.H. Wu (National Cheng Kung University, Taiwan) The effect of annealing on sandwiched Si/C/Si multilayers on a Si(100) substrate using ion beam sputtering (IBS) system under ultra high vacuum (UHV) were investigated. Carbon layer thickness was fixed at 100nm and a-Si ranged from 10nm to 50 nm. Rapid thermal annealing was performed to investigate the sp²-sp³ bonding evolution of temperature from RT to 750°C and time from 0.5 to 2 min. Raman spectroscopy was utilized to characterize bonding behavior of Si/C/Si multilayers for the variation of graphite peak (G peak), disorder-induced peak (D peak) at specific wavenumber shifts. The integrated intensity ratio (ID/IG) in the conventional DLC films was suggested to be correlated with the trend of more sp²-sp³ bonding ratio of amorphous carbon (a-C). The higher the ID/IG is, the more the sp² bonding is. From experimental result, the ID/IG ratio decreases with annealing time from 0.5m to 2m implies that the more formation of sp³ and Si-C bonding. The ID/IG ratio increases with annealing temperature from RT to 750°C implies that disorder peak would be getting higher with annealing temperature.
CP-25 Effects of Substrate Temperature on the Microstructure and Electrochromic Properties of Tungsten Oxide Films Prepared by Reactive Magnetron Sputtering H.-H. Lu (National Chin-Yi University of Technology, Taiwan) The electrochromic properties of tungsten oxide films have been extensively investigated due to their potential applications such as smart window of architecture and automobile glazing to save energy and modulate the transmittance of light and solar radiation. This paper reports the effects of substrate temperature on the composition, microstructure, and electrochromic properties of tungsten oxide films prepared by d.c. reactive magnetron sputtering. Experimental results showed that the crystallinity of films was obtained at the substrate temperature larger than 300°C. The optical band gap decreased with the substrate temperature increasing from room temperature to 350°C due to the existence of oxygen vacancies or larger grain size. The crystalline tungsten oxide films showed high reflectance in the near IR region. The transmittance of colored and bleached was reproducible after 100 cycles for amorphous and crystalline tungsten oxide films. It means the tungsten oxide films deposited by d.c. reactive magnetron sputtering had good quality stability.
CP-26 Improvement of Secondary Electron Emission Coefficient of MgO Protecting Layers for PDPs by Addition of GeO₂, SnO₂ L.Y. Chen, T. Ikawa, A. Nakao, S.H. Hsiao, Y. Tanaka, A. Ide-Ektessabi (Kyoto University, Japan) Magnesium oxide (MgO) thin films are widely used as protecting layers for AC-type plasma display panels (AC-PDPs), according to the properties of high secondary electron emission coefficients γ, high ion-induced sputtering resistance, high insulation and high transparency. Power consumption is the key issue for PDPs currently and it is correlated to the γ value. The higher γ results in less power consumption, because it is regarded that great numbers of electrons can decrease the firing voltage and the sustaining voltage. Consequently, it is important to develop new materials which possess higher γ for the PDPs industry. In this study, we focused on germanium oxide (GeO₂), tin oxide (SnO₂), which are oxides of the group 14 elements, and doped them to MgO thin films in various concentrations by electron beam evaporation. The relationship between the γ and the concentrations of each additive was investigated. Then properties of each oxide-doped film were compared. The surface roughness, the crystal orientation and the compositions of elements of thin films were measured by atomic force microscopy (AFM), X-ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS). The values of γ were calculated from Paschen’s law using breakdown voltages we measured. The different concentrations of each additive doping effected the properties of thin films, and it caused the change of γ characteristics.
CP-27 Effect of Rapid Thermal Annealing on the Properties and Hydrophilic Behavior of TaO_xN_y Thin Films J.H. Hsieh, C.C. Chang (Mingchi University of Technology, Taiwan) TaO_xN_y films were deposited by reactive sputtering with various ratios of O₂/N2 in Ar plasma. The films were annealed using RTA (Rapid Thermal Annealing) at various temperatures for different time. Then, the films were characterized using XRD, ellipsometry, and a contact angle measurement system. The results show that the as-deposited films were mostly amorphous. Annealing at temperatures higher than 700°C can transform these films to crystalline TaON phase. Hydrophilicity and optical properties of these films were found to be dependent on the annealing conditions and O₂/N2 ratios. At its best, complete wetting can be observed under visible light.

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