Sung-Bo Seo

Preparation of Transparent Metal Films, Titanium-Doped Zinc-Oxide Films (TiO2)2 (ZnO)98 on PEN by Using a RF-Magnetron Sputtering Method

In this work, (TiO2)x (ZnO)100-x (TZO) films were prepared on glass substrate at room temperature by RF-magnetron sputtering. The TZO film with x = 2 wt.% shows a very low resistivity of 4.7 × 10−4 Ω·cm which is comparable to that of ITO films and a high transmittance over 85% in the visible range. In particular, TiO2 (2wt.%)-doped ZnO (TZO) films with thicknesses ranging from 100 ∼ 500 nm were also prepared on Polyethylene naphthalate (PEN) substrates under various RF-powers. Their electrical property were investigated as a function of RF-power. This property was found to be closely related with the crystallization and density of TZO films. It was also noted that vaporization of the water and other adsorbed particles, such as organic solvents contained in most plastic substrate affect the properties of the TCO films.

Superhydrophobic surface obtained using pyramidal PTFE film fabricated on RIE etched silicon

We have developed a surface texturing process using a polytetrafluoroethylene coating with a pyramidal structure for obtaining superhydrophobic surfaces. In order to investigate the hydrophobic properties of the surface, we measured the contact angle and roughness values. The calculated roughness factor and root mean square roughness ranged from 2.47 to 2.6 and from 0.25 μm to 0.4 μm, respectively. The contact angle of a water droplet on the surface was greater than 150°; moreover, this angle was maintained for over 7 weeks. This observation implies that extremely low wettability is achievable on superhydrophobic surfaces.

Fabrication of superhydrophobic surface using surface texturing with nano-sized structure and PTFE film

We developed a superhydrophobic surface using surface texturing with nano-sized structure and polytetrafluoroethylene (PTFE) film deposition. The properties of superhydrophobic surface were investigated using water contact angle, root mean square (RMS) roughness, and X-ray photoelectron spectroscopy (XPS). The contact angle of a water droplet was greater than 150°, which means extremely low wettability is achievable on superhydrophobic surfaces. For nano-sized structure, we carried out two step etching process using reactive ion etching (RIE) in a large pyramid substrate by potassium hydroxide (KOH) solution. Metal mesh installed RIE etched silicon substrate using SF6 and O2 gas. PTFE films were deposited by conventional RF magnetron sputtering. This process is applicable for stable superhydrophobic and self-cleaning surfaces due to hierarchical structures formed silicon wafer etched by RIE technique.

Electrical Stabilities of In2O3-ZnO-SnO2 (IZTO) Films Against the External Stresses

ABSTRACT The (In2O3)77.34(ZnO)x(SnO2)22.66-x (denote to IZTO-2) films with x = 13, 15, 17, 19 wt.% were prepared on PET film with a 100-nm-thick SiO2 buffer layer by using RF-magnetron sputtering method, and their electrical stabilities were tested under various external stresses such as moist heat, temperature fluctuations and bending of substrate films. The lowest resistivity of 4.8 × 10−4 Ω•cm was observed in the IZTO-2 film of x = 17 wt.% which also had such good properties as high electrical stability, surface uniformity, and high conductivity as compared with those of another (In2O3)90(ZnO)7(SnO2)3 (IZTO-1) film. These results suggest that the optimum starting composition for IZTO film with high quality as a flexible transparent conducting oxide(TCO) film is In2O3 : ZnO : SnO2 = 77.34 : 17 : 5.66 wt.%. The electrical stability of the optimum IZTO-2 film was greatly improved because the SiO2 buffer layer introduced between IZTO thin film and PET substrate acted as a blocking barrier to water vapour and organic solvents diffusing from the PET film and also as a buffer layer withstanding the bending damage.

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.

The Electrical and Optical Properties of Ga-doped ZnO Films Prepared by Using Facing Target Sputtering System

(GZO) films were prepared at room temperature by using a facing target sputtering (FTS) system and their electrical resistivites was investigated as a function of the content. The GZO film with an atomic ratio of of x

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.

Post‐annealing Effects of CuInSe2(CIS)Absorber Layer at Thin Film Solar Cells with Compound Semiconductor Prepared by Co‐sputtering Method

In this study, we investigated the electrical and structural properties of CuInSe2(CIS) absorber layer with various post‐annealing temperatures in thin‐film solar cells prepared by co‐sputtering method. The CIS film annealed at 550 °C compared with the films without and with annealing temperatures below 550 °C has the main growth peaks of chalcopyrite‐like structure with CuInSe2 (112), CuInSe2 (220/204), and CuInSe2 (312/116), which resulted in increase of grain sizes and the improvement of crystallinity from the results of full width half maximum (FWHM) values and the intensity of peaks. And also, the carrier concentration and the mobility of the CIS thin film annealed at 550 °C were increased compared with the film without thermal treatment. Particularly, we suggest that the post‐annealing of the CIS absorber layer at an optimized temperature can be applied for improving the device efficiency at the thin‐film solar cells because the resistivity of the film annealed at 550 °C was decreased about 10−2 ord...

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(