Papers by Author: Chang Sik Son

Abstract: Multi-component ZnO-In2O3-SnO2 thin films have been prepared by RF magnetron co-sputtering using targets composed of In4Sn3O12(99.99%) [1] and ZnO(99.99%) at room temperature. In4Sn3O12 contains less In than commercial ITO, so that it lowers cost. Working pressure was held at 3 mtorr flowing Ar gas 20 sccm and sputtering time was 30 min. RF power ratio [RF1 / ( RF1 + RF2 )] of two guns in sputtering system was varied from 0 to 1. Each RF power was varied 0~100W respectively. The thicknesses of the films were 350~650nm. The composition concentrations of the each film were measured with EPMA and AES. The low resistivity of 1-2 × 10-3 and an average transmittance above 80% in the visible range were attained for the films over a range of δ (0.3 ≤ δ ≤ 0.5). The films also showed a high chemical stability with time and a good uniformity.

Abstract: We prepared the surface mounted white light emitting diode (LED) chips by using yellow phosphors on the blue LED chip. The optical and electrical properties of prepared white LED chips were investigated. The yellow phosphor mixed with transparent epoxy was coated on the prepared LED chip. The optimum mixing conditions with epoxy and yellow phosphor is obtained at the mixing ration of epoxy: yellow phosphor = 97 : 3 wt %. The maximum luminance and light emitting efficiency are above 80,000 cd/m2 and 23.2 lm/W, respectively, at the bias voltage of 2.9 V. There was no distinct change in the luminance strength with changing of the yellow phosphor ratios. The flowing current of the white LED chip is about 30 mA at 2.9 V.

Abstract: We investigated the effects of hydrogen annealing process on ferroelectricity in SrBi₂Ta₂O₉(SBT) capacitors. The hydrogen-induced degradation of SBT capacitors was found after a hydrogen annealing process. The degraded properties could be recovered by re-crystallization annealing process in O₂ ambient for 30 min. In order to prevent the catalyst reaction of Pt electrode known as an origin of hydrogen-induced degradation, Au top electrode was used. It was confirmed that Au electrode effectively prevented capacitors from degrading during hydrogen process.