Yong Seo Park

Properties of AZO/Ag/AZO Multilayer Thin Film Deposited on Polyethersulfone Substrate

The AZO/Ag/AZO multilayer films were deposited on polyethersulfone (PES) substrate by using facing target sputtering methods at room temperature. The AZO/Ag/AZO multilayer films with polymer substrate had advantages, such as low sheet resistance, high optical transmittance in visible range and stable mechanical properties. From the results, the AZO/Ag/AZO multilayer films (50/12/50 nm) demonstrated a sheet resistance of 11 Ω/□ and average transmittance of 87% in visible range (wavelength of 380-770 nm). Moreover, the multilayer showed stable mechanical properties compared to the single-layered AZO sample during the bending test due to the existence of the ductile Ag metal layer.

Electrical and optical properties of PLZT thin films on ITO coated glass by sol-gel processing

Sol-gel processed PLZT thin films were fabricated on ITO-coated glass substrates with RTA (rapid thermal annealing). The electrical and optical properties such as hysteresis curves, dielectric constant, dielectric loss and optical transmittance of thin films were investigated. The PLZT thin films were crystallized to the perovskite structure by RTA at 750°C for 5 min. As the La percentage was increased, the dielectric constant increased, and that of 9/65/35 PLZT thin film was 1750. The coercive field and remnant polarization decreased with La increase from 33.82 kV/cm to 14.71 kV/cm and from 39.26 μC/cm2 to 9.57 μC/cm2 respectively. As the Zr percentage increased at 2% La, the coercive field decreased from 52.94 kV/cm to 30 kV/cm, but the remnant polarization increased from 22.74 μC/cm2 to 50.75 μC/cm2, and the dielectric constant had a maximum value of 1269 at 2/55/45 composition. The optical transmittance was increased as La percentage increased but was decreased as the annealing temperature increased.

Photoluminescence Characteristics of Nanocrystalline ZnGa2O4 Phosphors Obtained at Different Sintering Temperatures

A nano-sized ZnGa2O4 phosphor was synthesized via a precipitation method (at a low temperature) and then sintered at various temperatures. X-ray diffraction (XRD) analysis confirmed that single-crystalline ZnGa2O4 particles were formed. A pure ZnGa2O4 phase was obtained at a sintering temperature of 1000°C. Theaverage size of the spherical ZnGa2O4-phosphor particles increased with increasing sintering temperature. The most intense photoluminescence (PL) peak – corresponding to blue emission at about 420 nm – was observed for the sample prepared at a sintering temperature of 1000°C.

Photoluminescence Characteristic of Ce3+-Eu3+ Co-doped Y3Al5O12 Phosphor Prepared by Combustion Method

For this study, Yttrium aluminum garnet (YAG) particles co-doped with Eu3+ and Ce3+ were prepared by combustion process using the 1:1 ratio of metal ions as reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and photoluminescence (PL). The various YAG peaks, with the (420) main peak, appeared at all Ce concentration in XRD patterns. The YAG phase crystallized with results that are in good agreement with the JCPDS diffraction file 33-0040. The SEM image showed that the resulting YAG:Ce,Eu powders had uniform sizes and good homogeneity. The grain size was about 50 nm. 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 of a broad band of Ce3+ activator, inclusive of the line peaks of Eu3+. The PL intensity of Ce3+ has the wavelengths of 480–650 nm and the PL intensity of Eu3+ has main peak at 590 nm.

Preparation of ZnO Based Thin Films for OLED Anode by Facing Targets Sputtering System

In this study, we prepared ZnO-based thin films-AZO, GZO and GAZO for OLED anode by facing targets sputtering (FTS) system. The reason of the used ZnO-based thin films is that it can be prepared to obtain high transparency in the visible range, low resistivity, stability of chemical and stability in hydrogen plasma by added materials such as Al, Ga. The electrical and optical properties of the as-doped AZO, GZO and GAZO thin films were evaluated with UV/VIS spectrometer, 4-point prove, XRD, AFM, FESEM. And the performance of the OLED device such as the operating voltage and its efficiency were evaluated by J-V-L (current density-voltage-luminance) measurements

Luminescence Characteristics of ZnGa2O4 Thick Film Doped with Mn2+ and Cr3+ at Various Sintering Temperatures

ZnGa2O4 phosphor separately doped with Mn2+ and Cr3+ was synthesized by solid-state reaction, and thick films were deposited by screen printing. The X-ray diffraction (XRD) patterns of ZnGa2O4 phosphor thick films show a (311) main peak and a spinal phase. Uniform distribution and filled morphology of the doped ZnGa2O4 phosphor thick films were formed at the sintering temperature of 1100 °C. The CL spectrum of Mn2+-doped ZnGa2O4 shows the main peak of 512 nm green emission with the 4T1→6A1 transition of Mn2+ ions and the CL spectrum of Cr3+-doped ZnGa2O4 shows the main peak of 716 nm red emission with the 2E→4A2 transition of Cr3+ ions.

Fabrication of Ag nanowire and Al-doped ZnO hybrid transparent electrodes

Among the materials used as transparent electrodes, silver nanowires (AgNWs) have attracted attention because of their high transmittance and excellent conductivity. However, AgNWs have shortcomings, including their poor adhesion, oxidation by atmospheric oxygen, and unstable characteristics at high temperature. To overcome these shortcomings, multi-layer thin films with an aluminum-doped zinc oxide (AZO)/AgNW/AZO structure were fabricated using facing targets sputtering. The samples heated to 350 °C exhibited stable electrical characteristics. In addition, the adhesion to the substrate was improved compared with AgNWs layer. The AZO/AgNW/AZO thin films with multilayer structure overcame the shortcomings of AgNWs, and we propose their use as transparent electrodes with excellent properties for optoelectronic applications.

Fabrication of ZnO/Ag Nanowire/ZnO Thin Films for Optoelectronic Applications

In order to improve the electrical properties of ZnO thin films to a level comparable with ITO transparent electrodes, silver nanowires (AgNWs) were coated between two ZnO layers as an inter-layer to produce a multilayer transparent conductive thin film. To achieve this, a uniform and stable AgNW layer was first formed by spin coating, onto which ZnO layers were deposited by facing target sputtering to protect against damage and oxidation. This structure was found to negate the drawbacks of each material layer, with a sheet resistance of 34.5 ohm/sq. and a transmittance of 84.5% being achieved.

Properties of ITO-stacked AgNWs films prepared on flexible substrates by low damage sputtering

ABSTRACT In this study, we fabricated the ITO-stacked AgNWs films on the various substrates and investigated their electrical, structural, and mechanical properties. Firstly, we coated Ag nanowires (AgNWs) layer on the soda-lime glass substrate and polymer substrate such as polyestersulfone (PES) and polycarbonate (PC) by using modified spin-coating method. And then, Indium Tin Oxide (ITO) film was deposited on coated-AgNWs layer by using facing targets magnetron sputtering (FTS) method at the room temperature. All samples prepared on various substrates have transmittance of about 80% in the visible range (300–800 nm) and low resistance of under 10 ohm/sq. And we investigated the properties of ITO-stacked AgNWs prepared on flexible substrate (PES, PC) by Lab-made bending machine. After substrate bending of 1000 times, the sheet resistance of prepared ITO single film 33.9 increased over 20000 ohm/sq and the sheet resistance of ITO-stacked AgNWs films increased from 8.38 to 19.33 ohm/sq in PES substrate and 6.69 to 24.42 ohm/sq in PC substrate.