Soon-ho Kim

Solid electrolyte aided studies of NO–CO reaction on Pd

Abstract The Pd-catalyzed NO–CO reaction at temperatures between 320 and 480°C exhibited electrochemical promotion. This reaction was performed in a fuel-cell configuration where Pd is coated on Y 2 O 3 -stabilized ZrO 2 . The electrochemical promotion of the catalytic activity and modification of the selectivity to N 2 O is reversible and this system showed both electrophilicity and electrophobicity, depending on the direction of oxygen ion pumping. In a typical experiment, the enhancement of reaction rate is 100 times greater than the rate of oxygen ion removal from the catalyst electrode. Rate enhancement, which is defined as the ratio of the reaction rate under electrochemical oxygen removal to the rate under open circuit, of ρ CO 2 =2.2, ρ N 2 O =2.2 and ρ N 2 =4.2 were measured for V WR =−1.8 V at 370°C.

Selective CO oxidation in the presence of hydrogen over supported Pt catalysts promoted with transition metals

Selective CO oxidation in the presence of excess hydrogen was studied over supported Pt catalysts promoted with various transition metal compounds such as Cr, Mn, Fe, Co, Ni, Cu, Zn, and Zr. CO chemisorption, XRD, TPR, and TPO were conducted to characterize active catalysts. Among them, Pt-Ni/γ-Al2O3 showed high CO conversions over wide reaction temperatures. For supported Pt-Ni catalysts, Alumina was superior to TiO2 and ZrO2 as a support. The catalytic activity at low temperatures increased with increasing the molar ratio of Ni/Pt. This accompanied the TPR peak shift to lower temperatures. The optimum molar ratio between Ni and Pt was determined to be 5. This Pt-Ni/γ A12O3 showed no decrease in CO conversion and CO2 selectivity for the selective CO oxidation in the presence of 2 vol% H2O and 20 vol% CO2. The bimetallic phase of Pt-Ni seems to give rise to stable activity with high CO2 selectivity in selective oxidation of CO in H2-rich stream.

ZrO2-supported Pt catalysts for water gas shift reaction and their non-pyrophoric property

Zirconia-supported platinum catalysts doped with cerium, nickel or cobalt (Pt-Ce/ZrO 2 , Pt-NilZrO 2 , Pt-Co/ZrO 2 ) were prepared by a single step co-impregnation method and their catalytic performance on the water gas shift reaction (WGS) were investigated. A Pt/Ce/ZrO 2 catalyst was also prepared impregnating ZrO 2 sequentially with Pt and Ce in order to compare the effects of impregnation methods on the catalytic activities of the final form of the catalysts. The results showed that the co-impregnated Pt-Ce/ZrO 2 catalyst was highly active for the WGS reaction at low temperatures (250 °C, GO conversion of 95.1%, feed composition of 10 vol% CO, 10 vol% CO 2 , and 80 vol% H 2 in dry base gas, H 2 O/CO=6, GHSV= 6000 h -1 ) and kept its activity even after air exposure in every cyclic test. The temperature programmed reduction (TPR) pattern of Pt-Ce/ZrO 2 indicated that the low reduction temperature of Pt induced by Ce gave rise to high activity on the WGS reaction. This Pt-Ce/ZrO 2 catalyst can be considered as an efficient catalyst for the WGS reaction, where high catalytic activity and non-pyrophoric property were required.

Selective CO removal in the H2-rich stream through a double-bed system composed of non-noble metal catalysts

Abstract The CO concentration in the effluent from the water-gas shift reactor can be reduced to be less than 15 ppm from about 1 vol through the double bed system composed of CuO-CeO2, which can oxidize CO selectively in the presence of excess H2, and Ni/Y-ZrO2, which is active for CO methanation in the presence of excess CO2, over a wide reaction temperature range.

Simple polarimetric method for electro-optic coefficients

A simple technique to measure electro-optic coefficients has been developed. It is based on rotating analyzer polarimetry. With a coaxial configuration of the optically active polarizing devices, the synchronously digitized signals are Fourier analyzed to quantitatively determine the elliptical polarization of light and, hence, the electric field induced birefringence. This technique has the advantage that it does not require waveguiding, and since it is improved from the crossed polarizer method it measures the phase retardation directly. It has been applied for the precise determination of electro-optic coefficients of uniaxial LiNbO3 single crystals. The excellent agreeement with reported values confirms its usefulness toward accurate characterization of electro-optic coefficients of unknown specimens.

Spectroscopic ellipsometric measurements of plasma-enhanced chemical vapour deposition-grown SiNxInP structure

InP has received considerable attention due to its large saturated electron drift velocity and the lower density of surface states at an insulator-Inp interface than at an insulator-GaAs interface. Silicon nitride films, formed by plasma-enhanced chemical vapour deposistion (PECVD), have many applications in compound semiconductor device fabrication and have been used mainly as passivation films for optoelectronic devices based on InP [1]. There have been various investigations into the structural properties of silicon nitride films on an InP substrate, viz. Auger electron spectoscopy (AES) [2], X-ray photoelectron spectroscopy (XPS) [3] and electron-spin resonance (ESR) [4] measurements, etc., but analysis based on the spectroscopic ellipsometer is rare. A spectoscopic ellipsometer is a surface analyser surpassing the limitations of the conventional ellipsometer, which is used in the non-destructive measurement of the thickness and quality of very thin films by using the characteristics of light, the phase of which is very sensitively changed with the existence of very thin films. Thus, its availability has extended to various surface and multilayer analyses [5 -81. In this letter we report spectroscopic ellipsometry measurements of SiNxln p (n-type) grown by PECVD with various NH3:SiH 4 ratios. A PECVD apparatus designed in-house [9] with a hot-wall capacitively coupled-type reactor was used to deposit the silicon nitride film using a diluted silane (5% Sill4 in N2), ammonia (99.999% purity) and nitrogen (99.9999% purity) gas mixture, on n-type wafers with (100) orientation and 1.3 x 1018 cm -3 electron concentration. The wafers were sequentially cleaned by standard organic solutions (trichloroethylene, acetone and methanol), and then rinsed in deionized water. The native oxide on the surface of the wafer was etched in an acid solution ( H 2 S O 4 : H 2 0 2 : H 2 0 = 3:1:1 ) for 60s and subsequently in an HF (49%) solution (HF:H20 = 1:1 ) for another 60 s. After rinsing in deionized water the wafers were blow-dried with nitrogen. For oxygenfree silicon nitride film the reactor was heated at 300 °C and purged with dry N2 gas flow for 1 h before silicon nitride deposition. We varied the NH3/SiH4 gas flow ratios from 0.205 to 0.686 at a substrate temperature of 300 °C, r.f. power of 60 W and total operation pressure of 66.7 Pa. The forma-

Hydrogen production by steam reforming of natural gas over highly stable Ru catalyst supported on Nanostructured Alumina

A nanostructured alumina (ANS) supported Ru catalyst was prepared and tested for the steam reforming of natural gas for hydrogen production. The Ru/ANS catalyst showed higher activity and stability through whole range of reaction conditions than catalysts consisting of commercial alumina as a support. The ANS, synthesized via a surfactant-driven pathway under a hydrothermal condition, exhibited a high thermal stability, a large pore volume and high surface area with fibrous morphologies. The results indicated that this ANS can be an efficient catalyst support for natural gas steam reforming.

The choice of mask in consideration of polarization effects at high NA system

Strong resolution enhancement techniques (RETs) are highly demanded to overcome the resolution limit of sub-60nm lithography. ArF immersion lithography may be the best candidate for sub-60nm device patterning. However, the polarization effect becomes more prominent to degrade the image quality in high NA immersion lithography as the feature size shrinks. Therefore, it is important to understand the polarization effect in the mask. The induced polarization effect shows the different aspects between the binary and the attenuated phase shift mask (PSM). In this paper, we considered the effects of polarization state as a function of mask properties. We evaluated the performances of the binary mask and the attenuated PSM by using simulation, AIMSTM (Aerial Image Measurement System) tool, and real wafer printing. We find out that there are no differences between the binary mask and the attenuated PSM in view of image contrast and mask error enhancement factor (MEEF).

Which Mask is Preferred for Sub-60 nm Node Imaging?

ArF immersion lithography may be the best candidate for sub-60 nm device patterning. However, the polarization effect is the most prominent root cause for the degradation of the image quality in high numerical aperture (NA) immersion lithography as the feature size shrinks. Therefore, it is important to understand the polarization effect in the mask. It is common knowledge that a small mask pattern is considered as the wave guide of transmission light. The induced polarization effect shows the different aspects between the conventional mask and the attenuated phase-shift mask (PSM). In this paper, we considered the effects of polarization state as a function of mask properties. The aerial image depends on the polarization states induced by the mask. We evaluated the performances of the conventional mask and the attenuated PSM by using the Solid-ETM simulation and AIMSTM (Aerial Image Measurement System) tool along with real wafer printing.

Monitoring system of CD error analysis for the 90-nm node mask manufacturing

CD(Critical Dimension) Non-Uniformity on a mask is normally separable into global and local CD errors by means of their error sources. In general a global CD error trend on a mask shows the properties of each process. On the other hand, local CD errors on a mask are pretty much random and caused from mainly measurement errors, LER(Line Edge Roughness), and litho-shot errors. However, because of its difficulty to pin point the sources of errors and correct them, the local CD errors are required more attention. A Global CD error trend on a mask can be classified into several groups. One originating from vacuum delay, lithography error, bake and etch process will cause a side error trend on a mask. Others are fogging, radial trends of develop, and etch loading. In order to classify all those global CD errors and local CD errors, the proper monitoring mask must be required. The works on this paper mainly focalize on minimizing global CD error trends on a mask by separating and analyzing error components with proper monitoring system of each process. We therefore, provide a monitoring mask designed for efficiently representing global and local CD errors in more detailed fashion which can analyze CD errors of each process and make feed-back to each process in order to improve each process of mask manufacturing.