Papers by Author: Deug Woo Lee

Abstract: M-CNTs (Multiwall Carbon Nano Tubes) can be used as an electrode, transferring electrons and heat very easily. This property helps transfer electrons created in TiO2 layer of DSSC (Dye-sensitized Solar Cell). CNTs layer with TiO2 utilized for the photocatalyst is expected to contribute to improve the efficiency of the solar cell. The Photocatalyst of TiO2 thin film was manufactured from titanium isopropoxide, ethanol, and HCl by a sol-gel process. To determine the property of TiO2 thin film with CNT, we performed to mix acid dispersed CNT in TiO2 Sol-gel and make coating membranes using sol-gel with different densities of CNT. It was found that the crystal structure changed from the anatase phase to the rutile phase having higher efficiency by XRD measure after treatment of high temperature sintering. To demonstrate the property of each sample, the transmittance of the TiO2 thin film was measured by a spectrometer and dispersion of CNT of the thin film was measured by SEM. In conclusion, the capacitance as the parameter which can affect performance of DSSC was investigated.

Abstract: Five degrees-of-freedom (DOF) motion errors of an ultra precision feed table were measured in this study. The laser interferometer was used to measure the yaw and pitch errors and the reversal method was used for the roll error measurement. The linear motion errors in the vertical and horizontal directions were measured using the sequential two point method. The influence of angular motion errors on the linear motion errors while applying the sequential two point method was compensated with the data from the laser interferometer and the reversal method. Capacitive type sensors and an optical straight edge were used while applying the reversal method and the sequential two point method. To demonstrate the effectiveness of our measuring scheme for the ultra precision feed tables, five DOF motion errors of a hydrostatic table driven by a linear motor were measured and presented. From the measured repeatabilities of 5 DOF error motions, it was estimated that the measuring accuracies were ±0.02 μm for the horizontal and vertical linear motion, ±0.04 arcsec for yaw motion, ±0.05 arcsec for pitch motion and ±0.02 arcsec for roll motion.

Abstract: Nano-scale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) was demonstrated. A specially designed cantilever with diamond tip allows the formation of damaged layer on silicon substrate by a simple scratching process. A thin damaged layer forms in the substrate along scanning path of the tip. The damaged layer withstands against wet chemical etching in aqueous KOH solution. Diamond tip acts as a patterning tool like mask film for lithography process. Hence these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D micro structures in nanometer range. This study demonstrates the fabrication processes of the micro cantilever and diamond tip as a tool for TNL. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano machining tool.