Papers by Author: Chung Hsin Lu

Abstract: Shallow trench isolation via chemical mechanical polishing (CMP-STI) tests of Si wafers using CeO₂ slurry were studied. The impact of CeO₂ slurry's solid concentration on the SiO₂ removal rate and the selectivity ratio The effects of the solid concentration of CeO₂ slurry on the removal rate of SiO₂ and selectivity (SiO₂/Si₃N₄) were investigated. The CeO₂ abrasive was well matched to the XRD standard pattern, confirming that it had a cubic phase and the absence of any impurities. The SEM image showed that CeO₂ primary particles had a spherical-like shape with a size within 30-60 nm. Additionally, the prepared CeO₂ slurry showed a relatively high dispersion level. The wettability degree of the CeO₂ slurry on top of the Si wafer surface was also sufficient. Furthermore, results from polishing tests indicated that both the SiO₂ removal rate and the selectivity increased linearly with a rise in CeO₂ solid concentration.

Abstract: The emission of Sn2+ ion can vary from blue to red depending on its co-ordination number in the host lattice. Since Sn2+ ion has strong absorption in the ultra-violet region and can act as a reducing agent, it is of interest to examine the effects of co-doping Sn2+ ions on the luminescence properties of Eu3+ ions in different inorganic phosphor materials. In the present work, Eu3+ and Sn2+ ions co-doped strontium phosphate phosphors were synthesized via a solid-state reaction method in air, argon and reducing atmosphere. The prepared samples were characterized via X-ray diffraction. It was observed that the prepared Eu3+-doped strontium phosphate phosphor material had enhanced Eu3+ emission upon excitation with 395 nm light.

Abstract: TiO2 sol with steady suspension and high photocatalytic activity was prepared via a precipitation-peptization method. The XRD results indicate that the TiO2 sol exhibited an anatase structure. TiO2 films on woven fabrics (carbon, PET and Nylon), prepared via dip-coating with TiO2 sol, were characterized by XRD and SEM analysis. The dependence of the woven fabrics properties on the amount of TiO2 coated and photocatalytic activity were also studied. When the diameter of fibers is smalle, large quantity of TiO2 is coated on woven fabrics leading to an improvement in the photocatalytic activity. It is observed that the photocatalytic activity of TiO2 film coated on woven fabrics exceeds that of TiO2 film coated on common glass substrate with the same surface area.

Abstract: The feasibility of an internal heating method for the fabrication of large-scale nanostructured TiO2 samples by high pressure/low temperature sintering is studied. The primary apparatus used is a piston-cylinder type. The arrangement inside the die cavity consists of a circular cylindrical green compact, a graphite furnace to heat the sample, an aluminum container to protect the sample and an aluminum silicate or lava tube for electrical insulation. When the sample inside the mold achieved the desired sintering temperature, the temperature of the thermally insulated mold stayed low enough not to damage the mold itself. An obtained cylindrical sample has dimensions of 12.7 mm (1/2 inch) in diameter by 28.6 mm (1 1/8 inch) long. Its average grain size is 64 nm and the Vicker’s hardness is 5.3 GPa.

Abstract: The photoluminescent properties of BaMgAl10O17: Eu2+ synthesized via a sol-gel process employing citric acid (CA) and ethylene glycol (EG) were investigated in this study. The photoluminescence intensity of Eu2+ emission increased with increase in the doping concentration of Eu2+ up to 15 at %. The photoluminescence intensity of BaMgAl10O17: Eu2+ also varied with the EG: CA ratio. SEM investigation indicates that the sol-gel derived particles exhibited an irregular shape. The EPR studies showed that Eu2+ ions occupied the sites with non-cubic symmetry in the prepared phosphors.

Abstract: Barium titanate powders were synthesized via a hydrothermal process at 120-180
using titanium oxide powder with different particle sizes as starting materials in this study. When micron-sized titanium oxide was used, pure perovskite phase was not formed because of the insufficient chemical reactivity of titanium oxide. However, as nano-sized titanium oxide was utilized, pure barium titanate was obtained after the hydrothermal process was performed at 180 oC. The effects of sintering temperature on the dielectric properties of barium titanate were also investigated. Densified ceramics with high dielectric constants were obtained after sintering at 1200oC.