Papers

ICMCTF2006 Session C3-2: Optical Thin Films for Active Devices and Microsystems

Monday, May 1, 2006 2:10 PM in Room Royal Palm 4-6

Monday Afternoon

Start	Invited?	Item
2:10 PM		C3-2-3 Filtered Vacuum Arc Deposition of Transparent Conducting Zn-Al-O Films V.N. Zhitomirsky, E. Çetinörgü, E. Adler, Yu. Rosenberg, A. Gladkikh, R.L. Boxman, S. Goldsmith (Tel-Aviv University, Israel) Transparent conducting Zn-Al-O and Zn-O thin films were deposited on glass substrates by filtered vacuum arc deposition, using a 200 A DC discharge between a cylindrical Zn-3 at.% Al or pure Zn cathode, respectively, and an annular copper anode. The plasma flux generated by the cathode spots was magnetically guided through a quarter-torus macroparticle filter to the substrate. Zn-Al-O or Zn-O films formed on room temperature glass substrates in oxygen background gas with pressure P=0.4-0.93 Pa. Deposition time was 300 s. The crystalline structure, composition, and electrical and optical properties of the films were studied as functions of P. The films were stored under ambient air conditions and their resistance monitored over a period of several months. The Zn-Al-O films deposited at P=0.4 Pa were opaque; the transparency increased with increasing P, and saturated at P>0.6 Pa. The Zn-Al-O films deposited at all P had a polycrystalline Wurtzite structure with strong preferred grain orientation of the c-axis normal to the substrate surface. Their thickness was in the range of 300-800 nm decreasing with P. In all films, the Al concentration was found to be 0.006-0.008 at.%, i.e., a few orders of magnitude lower than in the cathode material. However, even this low Al content influenced the film resistivity (ρ) and stability: ρ of the as-deposited Zn-Al-O films (6-8 mΩ-cm) was lower and more stable that that of the ZnO films (>12 mΩ-cm). ρ had a tendency to increase with time: for Zn-Al-O films deposited at P=0.47-0.6 Pa it first increased slowly (1.1-1.4 times) and then stabilized after 30-45 days, for P=0.67-0.93 Pa ρ measured 90 days after deposition was 2.5-3.5 times larger that that for as-deposited films, while for ZnO films ρ measured 60 days after deposition increased by a factor of >7 with respect to as-deposited films.
2:30 PM		C3-2-4 Deposition of Transparent Conducting Oxides at Low Energies Using an Oxygen-Ion-Beam-Assisted Technique for Top-Emitting Organic Light-Emitting Diodes C.H. Jeong, J.T. Lim, J.H. Lee, M.S. Kim, G.Y. Yeom (Sungkyunkwan University, Korea) Tin-doped indium-oxide (ITO), which is one of the transparent conducting oxides (TCOs), have been widely used as general electrodes for organic light-emitting diodes (OLEDs). To apply TCO as the cathode layer of top-emitting OLEDs, TCOs must have lower resistance and higher transmittance, and suitable work function. To fabricate a high performance top-emitting OLEDs with a high aperture ratio and a high resolution, IO cathode was deposited as a transparent conducting electrode, by using oxygen-ion-beam-assisted deposition (IBAD), on a device of glass/Ag (100 nm)/ITO (100 nm)/2-TNATA (60 nm)/NPB (20 nm)/Alq₃ (40 nm)/LiF (1 nm)/Al (2 nm)/Ag (x nm), and its characteristics were investigated. To minimize the damage to the organic layers and the oxidation of the Ag layer during the oxygen IBAD, two-step processing of IBAD composed of argon IBAD followed by oxygen IBAD were required. By the two-step IBAD processing of the IO thin film deposition, TEOLED devices having a light-emission from the IO capping layer could be fabricated successfully having the maximum luminescence of about 30,000 cd/m².
2:50 PM		C3-2-5 MgO Composite Materials for AC Type Plasma Display Panels Y. Tanaka, S.-H. Hsiao, Y. Morimoto, A. Nakao, A. Ide-Ektessabi (Kyoto University, Japan) A transparent layer, which protects electrodes from ion bombardment and supplies secondary electrons to discharge space, is one of key factors for AC type Plasma Display Panels (ac-PDPs) performance. MgO has been used a material for the transparent layer of ac-PDPs, and researchers focused on preparation and property of MgO films. Adding oxide metals to MgO is one of the ways to increase the secondary electron emissivity γ. In this study, the properties of the MgO composite films were investigated. ZnO was selected as the additive in this study. The purity of raw materials used as the evaporation source was 99.9%. They were made to prepare various desired composition of pellets. MgO pellet was also prepared as a reference material. We used electron beam deposition method in this study. The thin films were deposited on carbon substrates to evaluate the composition of the films, and silicon (100) substrates for other investigations. Basic parameters of the deposition were as follows. Background pressure was 2.010 ^-3Pa and oxygen was added to a gas pressure of 3.010^-2 Pa during the deposition. Deposition rate was 1.0 to 1.2nm/s. Temperature was at 250°C in chamber. After the deposition, the deposited silicon substrates were annealed at 400°C for 2hr under the air atmosphere. The compositions of the films were investigated useing RBS. The γ was evaluated with a self-developed analyzer. Surface characteristics were investigated using AFM and crystal orientation was evaluated using XRD. Experimental results suggest that the highest value of γ was observed between 0.1 at.% and 0.4 at.% of [Zn/(Zn+Mg)] concentration. Moreover the γ increased as RMS roughness was increased.
3:10 PM		C3-2-6 White Organic Light-Emitting Diodes from Three Emitter Layers M.S. Kim, C.H. Jeong, J.T. Lim, J.H. Lee, G.Y. Yeom (Sungkyunkwan University, Korea) In this study, to apply for an active-matrix top-emitting organic light-emitting diode (TEOLED) with a high aspect ratio and a high resolution, an efficient white TEOLED was fabricated by doping 4,4^T-bis(2,2-diphenyl-ethen-1-yl)diphenyl (DPVBi), a blue-emitting layer, with a red fluorescent dye of 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). The structure of TEOLED was composed of glass/Ag (100 nm)/ITO (100 nm)/2-TNATA (60 nm)/NPB (15 nm) DPVBi : DCJTB (30 nm, 0.3%)/Alq₃ (35 nm)/Li or Cs (0.5 nm)/Al (2 nm)/Ag (20 nm)/ITO (100 nm). In this structure, by the incomplete energy transfer from blue-emitting DPVBi to red-emitting DCJTB, a balanced white light-emission could be obtained. Also, in this study, the electron-transporting properties of the TEOELD were investigated as a function of a Cs or Li thickness through current density-voltage-brightness characteristics of the device to improve an external quantum efficiency and a power efficiency of the fabricated white TEOLED devices. Also, an aperture ratio of the fabricated white TEOLED was estimated to improve the reflectivity of anode (Ag/ITO) and the transmittance of cathode (Al/Ag/ITO).
3:30 PM		C3-2-7 Liquid Crystal Display (LCD)-Based Color Filter Film Fabricated by a Pigment-Based Colorant Resist Inks and Printing Technology H.-S. Koo (The University of Tokyo, Japan); P.C. Pan, M. Chen (Ming-Hsin University, Taiwan); T. Shibata (The University of Tokyo, Japan) Inkjet printing technology has technically implemented on color filter manufacturing due to many convenience, economic consideration, and other advantages. This technology offers an efficient and steady production procedure of color filter, especially large scale of panel, so that the fabricating cost and the yield ratio can be well controlled. The experiment is to implement inkjet printing technology on green and red color ink by changing the ink droplet number, and then checks the chromatic characteristics by measuring results from equipments. The results of greenish ink approach to the required measurement value of CIE chromaticity diagram for optimal droplet number as 47 droplets and the film thickness is 1.45m, and the optimal droplet quantity of reddish ink is 31 with the film thickness of 1.20m. Furthermore, the experiment results of greenish ink can achieve the light transmittance ratio approached to or over 85% whose wavelengths approach to the center value of spectrum distribution of 515nm. The result of reddish ink can over the transmittance ratio 98%, and the wavelengths can satisfy with the center value of spectrum of 640nm. With OLED, PLED, and OTFT fabricating cost reduction, inkjet printing technology can be adopted to become the mainstream method. Color Filter, TFT-LCD, Chromatic Diagram, Rib Wall, Inkjet Printing Technology, Pixel Cell, Greenish Ink, Reddish Ink, OLED, PLED, OTFT.
3:50 PM		C3-2-8 Organic Light Emitting Diodes Based on Dipiridamole Drug M. Cremona, C. Legnani, W.G. Quirino (Pontificia Universidade Catolica do Rio de Janeiro (PUC-RIO), Brazil); M. Tabak (USP, Brazil); S.R. Louro (Pontificia Universidade Catolica do Rio de Janeiro (PUC-RIO), Brazil) Organic electroluminescent diodes (OLEDs)represent a promising research line in the development of new optoelectronic components mainly due to the possibility to use the most different organic compounds. The research of new luminescent organic materials comes earning, therefore, a great impulse in the molecule search or organic complexes making possible applications. Dipyridamole (DIP) 2;6-bis(diethanolamino)-4;8-dipiperidinopyrimido (5;4-d)pyrimidine is a drug used in the medicine as vasodilators and as antiplatelet. This molecule presents, in solution, an intense fluorescence in the visible region whose intensity depends, also, of the pH value. In this work the results of the production and the characterization of OLEDs using the DIP as emitting and electron transporting layer are presented. A comparison between two different hole transporting layers (HTL), 1-(3-methylphenyl)-1,2,3,4 tetrahydroquinoline-6-carboxyaldehyde-1,1'-diphenylhydrazone (MTCD) and N,N-di(naphthalen-2-yl)-N, N-diphenyl-benzine (NPB), used in the devices is also reported. Organic materials were sequentially deposited by thermal evaporation onto indium tin oxide (ITO) glass substrates at room temperature in a high vacuum environment (5x10^-6 Torr). The junction is formed by a 35 nm thickness film of MTCD or NPB, a 80 nm thick layer of DIP working as light-emitting layer and finally by another 15 nm thick layer of tris 8-hydroxyquinoline aluminum (Alq₃)which is the electron transporting layer (ETL). Finally, an Aluminum electrode (120 nm) was evaporated onto the system. By applying a dc voltage at the electrodes in forward condition it was possible to observe room temperature electroluminescence (EL) emission in the active area of all the fabricated devices. The wide intense band, centered at 493 nm, can be attributed to the DIP S₀ to S₁ transitions with a π to π* nature. The differences between the use of the MTCD and NPB layers are discussed in the work.