Papers by Author: Duck Kyun Choi

Abstract: This paper describes examines the non-linearity of multilayer ceramic capacitors (MLCC) with new equivalent circuits. The electric charge quantity (Q) was measured as a function of applied voltage (V) under 16 V ac-field to validate the ferroelectricity of MLCC with capacitance of 1 μF. The Q-V curves predicted under ac-field using B2 spice software showed the non-linearity of ferroelectricity in the high ac-field. The Q-V curve predictions were in agreement with the experimental data for the MLCC.

Abstract: Electrochromic WO3 thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by a sol-gel dip coating method. The thermal analysis was conducted by DSC/TG method. A DSC/TG analysis and the XRD patterns showed that a tungsten oxide crystal phase was formed at 400oC. WO3 thin film when heat-treated at 300oC was amorphous and had a better electrochemical property than that of the crystalline phase. Crystallization of tungsten oxide decreased active sites of ion intercalation so that the current density decreased with heat-treatment temperature.

Abstract: Electrochromic WO3 thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by sol-gel dip coating method. XRD pattern showed that tungsten oxide crystal phase formed at 400
. In the view of electrochemical property, WO3 thin film which was heat-treated at 300
and was amorphous had better than that of the crystalline phase.

Abstract: In field aided lateral crystallization process which is one of the low temperature crystallization processes for the amorphous silicon films, the effect of the alternating field (AC voltage) instead of the static field (DC voltage) was investigated. Following the deposition of 2 nm thick Cu catalyst outside of the 5 mm bar patterns in the PECVD amorphous silicon film, the specimen was heated at 500°C in N₂ambient for 5 hours with applying 5 V/cm AC-field along with 30 V/cm DC-field. As compared to the case of 35 V/cm DC-field only, the specimen from both the 30 V/cm DC and 5 V/cm AC resulted in 1.5 times faster crystallization velocity, regardless of the experimental frequency ranges of 100 Hz ~ 50 MHz. Presumably, the enhancement of the crystallization velocity under the combined field is associated with the increase in the flux of the crucial diffusion species, Cu atoms, which govern the overall crystallization velocity due to the agitation effect by the AC-field.

Abstract: Considering practical application of field aided lateral crystallization process in channel region of thin film transistors, there might be a different crystallization behavior dependent on the shape of channel to be crystallized. In this study, channel array with various aspect ratios was prepared and the Cu field aided lateral crystallization process was carried out at 500ı for 10 hours with applying 30V/200㎛ through common electrodes for the sake of the actual channel area crystallization. Both the fraction of crystallized area and the degree of crystallization increase as the aspect ratio of channel become away from 1.