Seon-Hoon Kim

The study of light waveguide effects on ZnO nanorod arrays

Two different types of ZnO nanorods (hexagonal pyramid-shaped nanorod and hexagonal prism-shaped nanorod) were integrated on light emitting diodes (LEDs) for the investigation of light waveguide effects, which were evaluated using electroluminescence (EL) and current-voltage (I–V) characteristics. EL intensity in LEDs with hexagonal prism-shaped ZnO nanorod arrays were improved by 18% while EL intensity in LEDs with hexagonal pyramid-shaped ZnO nanorods were reduced by 25% compared to bare LEDs. 3D-finite dimension time domain (3D-FDTD) programs were used to simulate the light waveguide effect on the two different shapes of ZnO nanorods. In addition, photonic crystals (PCs) effects in ZnO nanorod arrays were simulated to verify the light waveguide effect. It was found that light in a hexagonal prism-shaped ZnO nanorod propagated from the bottom to the top end. However, the light in a hexagonal pyramid-shaped ZnO nanorod was dissipated on the lateral face. The light extraction efficiency in ZnO nanorod arrays was dominated by the top end shape and planar density of ZnO nanorods.

Effects of Substrate on the Characteristics of SnO 2 Thin Film Gas Sensors

Effects of substrate materials on the microstructure and the sensitivity of thin film gas sensors have been studied. Various substrates were studied, such as oxidized silicon, sapphire, polished alumina, and unpolished alumina. It was observed that strong correlation exists between the electrical resistance and the CO gas sensitivity of the manufactured sensors and the surface roughness of thin films, which in turn was related to the surface roughness of the original substrates. Xthin film gas sensor on unpolished alumina with the highest surface roughness showed the highest initial resistance and CO gas sensitivity. The transmission electron microscopy observation indicated that shape and size of the columnar microstructure of the thin films were not critically affected by the type of substrates.

Fabrication of Up-Conversion Phosphor Films on Flexible Substrates Using a Nanostructured Organo-Silicon

Up-conversion phosphors have attracted considerable attention because of their applications in solid-state lasers, optical communications, flat-panel displays, photovoltaic cells, and biological labels. Among them, NaYF4 is reported as one of the most efficient hosts for infrared to visible photon up-conversion of Yb3+ and Er3+ ions. However, a low-temperature method is required for industrial scale fabrication of photonic and optoelectronic devices on flexible organic substrates. In this study, hexagonal β-NaYF4: 3 mol% Yb3+, 3 mol% Er3+ up-conversion phosphor using Ca2+ was prepared by chemical solution method. Then, we synthesized a nanostructured organo-silicon compound from methyl tri-methoxysilane and 3-glycidoxy-propyl-trimethoxy-silane. The transmittance of the organo-silicon compound was found to be over 90% in the wavelength range of 400~1500 nm. Then we prepared a fluoride-based phosphor paste by mixing the organo-silicon compound with Na(Ca)YF4:Yb3+, Er3+. Subsequently, this paste was coated on polyethylene terephthalate, followed by heat-treatment at 120 °C. The visible emission of the infrared detection card was found to be at 655 nm and 661 nm an excitation wavelength of 980 nm.

Optical Characteristics of Plasmonic Nano-structure Using Polystyrene Nano-beads

Abstract: We proposed and demonstrated the double layered metallic nano-hole structure using polystyrene beads process to enhance the sensitivity of surface plasmon resonance (SPR). The double layered SPR structures are calculated using the finite-difference time-domain (FDTD) method for the width, thickness, and period of the metallic nano-hole structures. The thickness of the metal film and the metallic nano-hole is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The double layered SPR structures are fabricated with monolayer polystyrene beads of 420 nm wide. The sensitivities of the conventional SPR sensor and the double layered SPR sensor are obtained to 42.2 and 52.1 degree/RIU, respectively. Keywords: Surface plasmon resonance, Metallic nano-hole, Sensor, Polystyrene, FDTD 1. 서 론 1) 최근 바이오 물질의 비표지 검출 방법으로 굴절률의 변화를 측정하여 생체 물질의 상호작용을 인지할 수 있는 표면 플라즈몬 공명(surface plasmon resonance, SPR) 센서에 관한 연구가 활발히 이루어

Optical Characteristics of Plamonic Waveguide Using Tapered Structure

Laboratory for Electromagnetic Field and Microwave Electronics, ETH Zurich, Zurich 8092, Switzerland(Received January 23, 2014; Revised February 3, 2014; Accepted February 19, 2014)Abstract: We have investigated the optical properties of plamonic waveguide with tapered structure based on InP material for photonic integrated circuit(PIC). The proposed plasmonic waveguide is covered with the Ag thin film to generate the plasmonic wave on metallic interface. The optical characteristics of plasmonic waveguide were calculated using the three-dimensional finite-difference time-domain method. The plasmonic waveguide was fabricated with the lengths of 2 to 10 μm and the widths of 400 to 700 nm, respectively. The plasmonic mode and optical loss were measured. The optimum plasmonic length is 10 μm and widths are 600 and 700 nm in the fabricated waveguide. This plasmonic waveguide can be directly integrated with other conventional optical devices and can be essential building blocks of PIC. Keywords: FDTDSurface plasmon resonance, Plamonic waveguide, Tapered structure, PIC,

The surface plasmon resonance sensor with the metallic nanostructure for biosensing

In this paper, we have demonstrated a metallic nano-structured SPR sensor for an improvement of biosensing sensitivity using a metallic nano-structure. Permittivity of metal is calculated with Drude model for analysis. The sensitivity of SPR sensor with metallic nano-structure is 65 degree/RIU, and that of conventional SPR configuration is 54.8 degree/RIU. We have fabricated the random metallic nano-structures on the metallic thin film using the RIE etching process. Moreover, we have analyzed the structure using the finite-difference time-domain method for the exact characteristic.

Photoelectric Conversion Efficiency of DSSC According to Plasma Surface Treatment of Conductive Substrate

This study is explore the photoelectric conversion change of dye-sensitized solar cells with surface treatment of the conductive substrate. gases of FTO surface treatment were N2, and O2. Treatment conditions of surface were gas flux from 25 sccm to 50 sccm and RF power were from 25 W to 50 W. Treatment time and pressure were fixed 5 min and 100 mtoor. The best sheet resistance and surface roughness were obtained by O2 50 sccm and 50 W and that result were 7.643 Ω/㎠ and 17.113 nm, respectively. The best efficiency result was obtained by O2 50 sccm and 50 W and that result of Voc, Jsc, FF and efficiency were 7.03 V, 14.88 mA/㎠, 63.75% and 6.67%, respectively.

Synthesis of TiO 2 by Sol-gel Method and Electrochemical Properties of DSSCs with Controlling pH

The sol-gel method has been widely used to synthesize the for dye sensitized solar cells and has advantages of easily fabrication process, controlling the phase and getting transparent thin-film composed of the . In this paper, we synthesized the crystalline by sol-gel method controlled by the quantity ratio of Nitric acid and Ammonium hydroxide additives. The best efficiency result was obtained by 0.05 M Ammonium hydroxide and that results of Voc, Jsc, FF, and efficiency were 0.68 V, 3.28 mA/, 58.14 and 5.21%, respectively.

Fabrication of 2D Bravais Nano Pattern and Growth of ZnO Nano Rods with Photonic Crystal Effect

Two-dimensional (2D) nano patterns including a two-dimensional Bravais lattice were fabricated by laser interference lithography using a two step exposure process. After the first exposure, the substrate itself was rotated by a certain angle, for a square or rectangular lattice, for an oblique lattice, and for a hexagonal lattice, and the and laser incident angle changed for rectangular and the and laser incident angle changed for a centered rectangular; we then carried out a second exposure process to form 2D bravais lattices. The band structure of five different 2D nano patterns was simulated by a beam propagation program. The presence of the band-gap effect was shown in an oblique and hexagonal structure. The oblique latticed ZnO nano-photonic crystal array had a pseudo-bandgap at a frequency of 0.337-0.375, 0.575-0.596 and 0.858-0.870. The hexagonal latticed ZnO nano-crystallite array had a pseudo-bandgap at a frequency of 0.335-0.384 and 0.585-0.645. The ZnO nano structure with an oblique and hexagonal structure was grown through the patterned opening window area by a hydrothermal method. The morphology of 2D nano patterns and ZnO nano structures were investigated by atomic force microscopy and scanning electron microscopy. The diameter of the opening window was approximately 250 nm. The height and width of ZnO nano-photonic crystals were 380 nm and 250 nm, respectively.