Sun-Young Sohn

Transparent Conductive Oxide (TCO) Films for Organic Light Emissive Devices (OLEDs)

Transparent conducting oxide (TCO) thin films of In2O3, SnO2, ZnO, and their mixtures have been extensively used in optoelectronic applications such as transparent electrodes in touch panels, flat panel displays (FPDs), and other future devices. The first chapter provides an introduction to the basic physics of TCO films and surveys the various topics and challenges in this field. It includes a description of the TCO materials used in some of the organic light emissive devices (OLEDs) that have been studied extensively to date, the performance of various OLEDs, and a brief outlook. Chapter 2 focuses on TCO material development of p-type and n-type. Typical oxide kind of TCO materials consist of In2O3, SnO2, and ZnO. These are applied as a TCO films with ntype semiconducting property according to highly doped dopants which acting as a carrier. Until today, in a n-type TCO materials, indium tin oxide (ITO) doped with SnO2 of 10 wt.% in In2O3 has been widely commercialized. This is because the ITO film has high performance of both good electrical conductivity of ~10-4 Ω·cm and high transmittance of ~90% when the ITO film is coated on glass substrate. At present, In2O3-SnO2 (ITO) films are most commonly used as TCO films, but they have ome disadvantages, such as high cost, instability, poor surface roughness, and toxicity in their further applications. And amorphous ITO film deposited at low temperature has low resistance under moist heat, which leads to a decrease in its conductivity and light transmittance. In addition, unfortunately, the price of Indium is dramatically increasing every day due to a mix-up between the supply and demand of raw materials by the exhaustion of Indium source. On the other hand, some zinc-based TCO materials have good optical and electrical properties comparable to the ITO films, as well as low cost, high stability, excellent surface uniformity, and good etching selectivity. The zincbased TCO films are, therefore, regarded as promising substitutes for ITO film. In Chapter 3, the Indium-based and Zinc-based TCO Materials, and their electrical, optical, and structural properties will be discussed. Particularly, since more stringent specifications for TCO films have been required for realization of both higher resolution and larger screen size of FPDs, and preparation of high-quality TCO films at low temperature is very important to realize advanced optoelectronic devices. Chapter 4 will introduce the new TCO materials, such as: organic conductors like poly(3,4ethylenedioxy thiophene):poly(styrenesulphonicacid) (PEDOT:PSS), and the expanding field of nanomaterials including carbon nanotubes, nanoparticles, and composite materials combining one or more of these materials. For example, long metallic nanotubes have been

A Stable Super-Hydrophobic and Self-Cleaning Al Surface Formed by Using Roughness Combined with Hydrophobic Coatings

A stable super-hydrophobic and self-cleaning surface with a high contact angle above 150° and the contact angle hysteresis below 3° were produced by using roughness combined with hydrophobic coatings, which were also confirmed to exhibit extreme water repellence and self-cleaning properties which facilitate removal of contaminant particles. To fabricate micro-patterened aluminium surface, the aluminium was etched with hydrochloric acid. A very thin polytetrafluoroethylene (PTFE) film was coated on the etched aluminium surface in order to achieve the super-hydrophobic surface. Roughness factors on the aluminium surfaces coated with PTFE were calculated as a function of etching time, based on the homogeneous interface (Wensel model). A critical roughness factor on the super-hydrophobic surface of the aluminium coated with PTFE was found to be 1.51 which can be formed on the surface of the aluminium etched over 10 min with hydrochloric acid of 7 wt.%.

Properties of ZrO 2 Gas Barrier Film using Facing Target Sputtering System with Low Temperature Deposition Process for Flexible Displays

film was deposited by facing target sputtering (FTS) system on polyethylene naphthalate (PEN) substrate as a gas barrier layer for flexible organic light emitting devices (FOLEDs), In order to control the heat of the FTS system caused by the ion bombardment in the cathode compared with the conventional sputtering system, the process characteristics of the FTS apparatus are investigated under various sputtering conditions such as the distance between two targets (), the distance between the target and the substrate (), and the deposition time. The film by the FTS system can reduce the damage on the films because the ion bombardment with high-energy particles like gamma-electrons, Moreover, the film with optimized condition (

Hydrophobic Properties on RF-sputtered PTFE Films coated on UV-treated Glass Substrates

Surface properties of polytetrafluoroethylene(PTFE) films fabricated by rf-magnetron sputtering system with UV surface treatment were investigated to increase water contact angle for their hydrophobic property. We found that the surface morphology and water contact angles of PTFE film modified as a function of the UV treatment times using UV-irradiation were influenced. The water contact angle of PTFE film with optimized UV treatment time for 15 minute showed a high hydrophobicity compared with the film without any surface treatment. We thought that it was due to the energy change of PTFE surface with an adhesion improvement to the glass surface as a smoothing a rough surface with needle-shape and/or the enhancement of an interface property as a removing some defects on the surface like a cleaning effect.

Characteristics of AlN Dielectric Layer for Metal PCB as a Function of Nitrogen Partial Pressure Using RF-Magnetron Sputtering Method

In this investigation, the effects of gas partial pressure on the structural, electrical, and thermal properties of AlN dielectric layers prepared on aluminum substrates using RF-magnetron sputtering method were analyzed. Among the films, the AlN dielectric film deposited under gas partial pressure of 75% exhibit the highest AlN (002) preferred orientation, which was grain size of about 15.32 nm and very dense structure. We suggest the possibilities of it`s application as a dielectric layer for metal PCB because the AlN films prepared at optimized gas partial pressure can improving the insulating property, the thermal conductivity, and thermal diffusivity of the films.

Characteristics of SiO 2 Gas Barrier Films as a Function of Process Conditions in Facing Target Sputtering (FTS) System

For the silicon oxide films prepared by using the facing target sputtering (FTS) apparatus that was manufactured to enhance the preciseness of the fabricated thin-film and sputtering yield rate by forming a higher-density plasma in the electrical discharge space for using it as a thin-film passivation system for flexible organic light emitting devices (FOLEDs). The deposition characteristics were investigated under various process conditions, such as array of the cathode magnets, oxygen concentration introduced during deposition, and variations of distance between two targets and working pressure. We report that the optimum conditions for our FTS apparatus for the deposition of the films are as follows: are 90mm and 120mm, respectively and the maximum deposition rate is obtained under a gas pressure of 2 mTorr with an oxygen concentration of 3.3%. Under this optimum conditions, it was found that the film was grown with a very high deposition rate of /min by rf-power of , which was significantly enhanced as compared with a deposition rate (/min) of the conventional sputtering system. We also reported that the FTS system is a suitable method for the high speed and the low temperature deposition, the plasma free deposition, and the mass-production.

Photocatalyst Surface Properties of the Oxide Thin Films According to the Plasma Etching Process

, , and films with hydrophilic property are deposited by rf-magnetron sputtering. Their wettability is strongly depends on the presence or absence of the oxygen plasma etching on the glass substrates. The film of 50 nm-thick on the plasma etched glass shows a water contact angle (WCA) below which means a super-hydrophilic surface. However, WCA values are gradually degraded when the films are exposed under atmosphere, especially . In order to improve hydrophilic property, the degraded films can be again recovered by UV illumination for 10 sec using UV-light and the film shows a super-hydrophilic surface about .

Preparation of Transparent Metal Films, Gallium-Doped Zinc-Oxide (Ga2O3)x (ZnO)100-x Films by Using Facing Target Sputtering System

(Ga2O3)x(ZnO)100-x, x = 3, 5, 7, 9 wt.%, (GZO) films were prepared at room temperature by using a conventional rf-magnetron sputtering method. Their electrical resistivity was investigated as a function of the Ga2O3 content. The GZO film with x = 7 wt.%, shows the lowest resistivity of 1.5×10−3Ω. cm. This GZO films were also prepared at various substrate temperatures from room temperature to 400°C, Their electrical resistivity was found to be improved as the substrate temperature was increased, A very low resistivity of 4.5×10−4Ω.cm was obtained in the film prepared at the substrate temperature of 300°C. In addition, we found that the GZO films prepared by using facing target sputtering (FTS) system showed a dramatically improved conductivity as compared with that of the film prepared by the conventional sputtering system. In particular, we also found that the lowest resistivity of 2.8×10−4Ω.cm that is almost comparable with that of ITO film was obtained in the GZO films prepared at the substrate temperature of 300°C by using the facing target sputtering (FTS) system.

Homogeneous Al2O3 Multilayered Films Deposited on Poly(ethylene terephthalate) by Facing-Target Sputtering System for Thin-Film Passivation of Organic Light-Emitting Diodes

Homogeneous multilayered barrier films were fabricated by means of reactive and nonreactive processes using Al2O3 with the facing-target sputtering (FTS) system. The multilayered films showed 60% improved barrier performance and their fabrication was 30% faster than that of single Al2O3 layers of the same thickness. The water vapor transmission rate was increased up to the order of 10-4 gm-2d-1 from a three-pair system of reactive and nonreactive sputtered Al2O3 bilayers.

Properties of Transparent Conductive IGZO Thin Films Deposited at Various Substrate Temperatures

In this study, we investigated the optical, electrical, and structural properties of the IGZO(