Papers by Author: Han Ki Kim

Abstract: Electrical, optical, and structural properties of amorphous indium zinc oxide (IZO) anode films grown on flexible polycarbonate (PC) substrate were investigated. The x-ray diffraction (XRD) result shows that the IZO film grown at room temperature is complete amorphous structure due to low substrate temperature. A sheet resistance of 34.1 ,/
, average transmittance above 88.9% in visible range, and root mean spare roughness of 3.5~10.5 Å were obtained even in the amorphous IZO anode film grown on PC substrate at room temperature. It is shown that the Ir(ppy)3 doped-flexible organic light emitting diode (OLED) fabricated on the amorphous IZO anode exhibit comparable current-voltage-luminance characteristics as well as external quantum efficiency and power efficiency to OLED fabricated on conventional ITO/glass substrate. These findings indicate that the IZO anode film is a promising anode material for the fabrication of flexible OLEDs.

Abstract: ZnO nanowalls and nanocolumns were synthesized on Si3N4 (50 nm)/Si (001) substrates at low growth temperature (350 and 400 oC) by metalorganic chemical vapor deposition (MOCVD) with no metal catalysts. ZnO nanowalls with extremely small wall thicknesses below 10 nm and nanocolumns with diameters over 100 nm were formed on the Si3N4/Si substrates relying on MOCVD-growth temperature. It was found that ZnO nanowalls have a strong c-axis preferred orientation with a hexagonal structure, while ZnO nanocolumns have a weak c-axis preferred orientation with broken stacking orders in synchrotron x-ray scattering experiments. In addition, strong free-exciton emission from the ZnO nanowalls was clearly observed in photoluminescence measurements. On the other hand, we could not observe any emission bands from the ZnO nanocolumn samples.