• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.15-21
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• 1993

This paper describes the design and development of a KrF excimer laser stepper and discusses the detailed system parameters and characterization data obtained from the performance test. We have developed a deep UV step-and-repeat system, operating at 248 nm, by retrofitting a commercial modules such as KrF excimer laser, precision wafer stage and fused silica illumination and 5X projection optics of numerical aperture 0.42. What we have developed, to the basic structure, are wafer alignment optics, reticle alignment system, autofocusing/leveling mechanisms and environment chamber. Finally, all these subsystem were integrated under the control of microprocessor-based controllers and computer. The wafer alignment system comprises the OFF-AXIS and the TTL alignment. The OFF-AXIS alignment system was realized with two kinds of optics. One is the magnification system with the image processing technique and the other is He-Ne laser diffraction type system using the alignment grating on the wafer. 'The TTL alignment system employs a dual beam inteferometric method, which takes advantages of higher diffraction efficiency compared with other TTL type alignment systems. As the results, alignment accuracy for OFF-AXIS and TTL alignment system were obtained within 0.1 $\mu\textrm{m}$/ 3 $\sigma$ for the various substrate on the wafers. The wafer focusing and leveling system is modified version of the conventional systems using position sensitive detectors (PSD). This type of detection method showed focusing and leveling accuracies of about $\pm$ 0.1 $\mu\textrm{m}$ and $\pm$ 0.5 arcsec, respectively. From the CD measurement, we obtained 0.4 $\mu\textrm{m}$ resolution features over the full field with routine use, and 0.3 $\mu\textrm{m}$ resolution was attainable under more strict conditions.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.1
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• pp.43-50
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• 2008

Ceramides, a constituent of stratum corneum lipids, play a crucial role in the formation and maintenance of the epidermal permeability barrier. As in many other skin disorders, atopic dermatitis and psoriasis show decrease and transformation of the ceramides. The application of ceramide has been demonstrated to be efficient in the repair of these skin disorders. Nevertheless, natural ceramides are still too expensive and small in quantity to be used as a cosmetic ingredient. Although a lot of pseudo-ceramides have been developed and on the market until now, those pseudo-ceramides did not fully meet the consumer's needs, therefore, there is still a demand for a novel pseudo-ceramides. We synthesized a novel pseudo-ceramide BPC-16 from 2-(2-amino-ethylamino)-ethanol(AEEA), which was characterized by structures having both amide bonds and hydroxyl groups as hydrophilic units, as well as two long alkyl chains. We formulated emulsion with BPC-16, cholesterol, stearic acid, and other components to make an emulsion. These emulsion showed a typical optical anisotropy on cross-polarized microscopy. This 'Maltese cross' appearance is a characteristic figure observed in concentric lamellar emulsion under cross-polarized microscopy. In cytotoxicity assay using MTT in monolayer and three dimension(3D) cell culture, a BPC-16 showed only negligible cytotoxicity up to the effective concentration for barrier repair and moisturization(less than 10 mM). In the measurement of TEWL, this BPC-16 showed significant recovery of water-retaining properties when it was topically applied to either SDS-induced dry skin or normal skin compared to that of base cream. This novel pseudo-ceramide BPC-16 showed as effective in skin barrier repair and moisturization as natural ceramides.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.224-229
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• 2010

Indium oxide $(In_2O_3)$ thin films have been prepared on glass substrate by using radio-frequency reactive magnetron sputtering with changing the oxygen flow ratio. The substrate temperature was kept at a fixed value of $400^{\circ}C$, and the sputtering gas and reactive gas were supplied with argon and oxygen, respectively. The oxygen partial flow ratio was varied by controlling the amount of oxygen with respect to the total mixed gases, 10%, 20%, 30%, 40%, and 50%. The optical, electrical, and structural properties of the deposited thin films were investigated by using ultraviolet-visible-near infrared spectrophotometer, Hall measurement, and X-ray diffractometer and scanning electron microscopy. The $In_2O_3$ thin film deposited at 20% of oxygen flow ratio showed an average transmittance of 86% in the wavelength range of 430~1,100 nm, an electrical resistivity of $1.1{\times}10^{-1}{\Omega}cm$. The results show that the transparent conducting films with optimum conditions can be achieved by controlling the oxygen flow ratio.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.217-223
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• 2010

We grew multi-stacked InAs/$In_{0.1}Ga_{0.9}As$ DWELL (dot-in-a-well) structure by metal organic chemical vapor deposition and investigated optical properties by photoluminescence and I-V characteristics by dark current measurement. When stacking InAs quantum dots (QDs) with same growth parameter, the size and density of QDs were changed, resulting in the bimodal emission peak. By decreasing the flow rate of TMIn, we achieved the uniform multi-stacked QD structure which had the single emission peak and high PL intensity. As the growth temperature of n-type GaAs top contact layer (TCL) is above $600^{\circ}C$, the PL intensity severely decreased and dark current level increased. At bias of 0.5 V, the activation energy for temperature dependence of dark current decreased from 106 meV to 48 meV with increasing the growth temperature of n-type GaAs TCL from 580 to $650^{\circ}C$. This suggest that the thermal escape of bounded electrons and non-radiative transition become dominant due to the thermal inter-diffusion at the interface between InAs QDs and $In_{0.1}Ga_{0.9}As$ well layer.

• Korean Journal of Materials Research
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• v.8 no.8
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• pp.693-698
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• 1998

The effects of $AI_{2}$$O_{3}$ and the ratio of $Na_2O/B_2O_3$ on the phase separation and optical properties of sodium borosilicate glass film fabricated by AFD(Aerosol Flame Deposition) were investigated. When AI,O, of 6wt% was added to $66SiO_2-27B_2O_3-7Na_2O$ the clear glass film without any crystallization was produced under air-quenching condition after consolidation. As the amount of $AI_{2}$$O_{3}$ increased from 1.5 to 6.0 wt% the refractive index linearly increased from 1.4610 to 1.4701, and the difference of TE and TM mode causing by residual stress in film increased gradually. However, the difference of TE and TM mode to reveal birefringence could be minimized by annealing below the glass transition temperature after consolidation and air quenching. On the other hand. as the ratio of $Na_2O/B_2O_3$ increased the refractive index and birefringence of glass film tended to increase, but the measurement of their values were not available at over the critical ratio of $Na_2O/B_2O_3$, because of the cloudiness due to crystallization. The phase separation was greatly accelerated with increasing the ratio of $Na_2O/B_2O_3$.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.453-459
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• 2001

It is important for the fabrication of nuclear cladding to optimize the microstructure, because the properties of Zr-based nuclear claddings such as mechanical properties, oxidation-resistance and corrosion- resistance vary widely with its microstructure. The microstructure in Zr-based alloy is strongly dependent on the solubility of alloying element. However, it is very difficult to measure the solubility due to the low solution limit of alloying elements in Zr-based alloy. In this study, Thermoelectric Power(TEP) measurements are used to determine the solubility of Nb in Zr-0.8Sn alloy, which is confirmed by optical microscopy and transmission electron microscopy. The solutioning of Nb obtained by a homogenization treatment and water-quench leads to a decrease of TEP The saturation of TEP appears with the increase of homogenization temperature, which means the saturation of the Nb content in the matrix. From these results, the solubility ($C_{Nb}$) of Nb in Zr-0.8Sn with temperature could be expressed as fellow equation : $4.69097{\times}10^{16}{\times}e^{-25300\times\;I/T}$(ppm.at.%)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.154-154
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• 2006

Samsung Electro Mechanics ink jet has developed ultra high resolution alignment system. The alignment system has been developed for repeatable printing of conductive ink. The resolution of alignment system is 0.5um and the velocity of printing working plate is 1.5m/s. So far repeated printing results included sintering process have over 30um of drop mislocation data. In order to improve line thickness and conductivity of metal line, we need to develop the higher mechanical accurate align system. On the demand, this developed align system has under $1{\sim}2{\mu}m$ mispositioning performance and can measure of mechanical accuracy of inkjet printer, as well as the straightness of jetted drop from inkjet head. There is no kinds limit of substrate and ink to use SEM alignment system. By using this alignment system, we progress two experiment of reiterate printing drop and making conductive line on the glass and photo paper. Optical microscope and 3D profiler has been used for measurement of printed ink.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.97-97
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• 2013

Recently, Cu2ZnSn(S,Se)4 (CZTSS), which is one of the In- and Ga- free absorber materials, has been attracted considerable attention as a new candidate for use as an absorber material in thin film solar cells. The CZTSS-based absorber material has outstanding characteristics such as band gap energy of 1.0 eV to 1.5 eV, high absorption coefficient on the order of 104 cm-1, and high theoretical conversion efficiency of 32.2% in thin film solar cells. Despite these promising characteristics, research into CZTSS based thin film solar cells is still incomprehensive and related reports are quite few compared to those for CIGS thin film solar cells, which show high efficiency of over 20%. I will briefly overview the recent technological development of CZTSS thin film solar cells and then introduce our research results mainly related to sputter based process. CZTSS thin film solar cells are prepared by sulfurization of stacked both metallic and sulfide precursors. Sulfurization process was performed in both furnace annealing system and rapid thermal processing system using S powder as well as 5% diluted H2S gas source at various annealing temperatures ranging from $520^{\circ}C$ to $580^{\circ}C$. Structural, optical, microstructural, and electrical properties of absorber layers were characterized using XRD, SEM, TEM, UV-Vis spectroscopy, Hall-measurement, TRPL, etc. The effects of processing parameters, such as composition ratio, sulfurization pressure, and sulfurization temperature on the properties of CZTSS absorber layers will be discussed in detail. CZTSS thin film solar cell fabricated using metallic precursors shows maximum cell efficiency of 6.9% with Jsc of 25.2 mA/cm2, Voc of 469 mV, and fill factor of 59.1% and CZTS thin film solar cell using sulfide precursors shows that of 4.5% with Jsc of 19.8 mA/cm2, Voc of 492 mV, and fill factor of 46.2%. In addition, other research activities in our lab related to the formation of CZTS absorber layers using solution based processes such as electro-deposition, chemical solution deposition, nano-particle formation will be introduced briefly.

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.104-114
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• 2001

To investigate the effects of the addition of Nb and Sn on the recrystallization of Zr- Sn-Nb alloys, both Vickers micro-hardness test and TEP measurement were carried out on cold-worked specimens annealed at various temperatures from $300^{\circ}C$ to 75$0^{\circ}C$. The microstructures of heat treated specimens were analyzed by optical microscope, SEM, and TEM. The study of microhardness and microstructures showed that both recrystallization process and grain growth were retarded as the activation energy was increased by the addition of Nb and Sn. Especially, the addition of Sn was more effective on retarding recrystallization. Precipitates were formed more easily when Nb was added because the solubility of Nb into Zr is lower than that of Sn. However, the recrystallization process was affected more by Sn than Nb because the strain field formed by substitutional Sn repressed the dislocation movement. TEP was increased due to the decrease of electron scattering as recovery and recrystallization were proceeded and saturated when the recrystallization completed. However, when precipitates formed, TEP was increased because the decrease of solute concentration near the precipitates caused the decrease of electron scattering.

• Korean Journal of Remote Sensing
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• v.16 no.3
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• pp.221-233
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• 2000

An intertidal topography is continuously changed due to morphodynamics processes. Detection and measurement of topographic change for a tidal flat is important to make an integrated coastal area management plan as well as to carry out sedimentologic study. The objective of this study is to generate intertidal DEM using leveling data and waterlines extracted from optical and microwave remotely sensed data in a relatively short period. Waterline is defined as the border line between exposed tidal flat and water body. The contour of the terrain height in tidal flat is equivalent to the waterline. One can utilize satellite images to generate intertidal DEM over large areas. Extraction of the waterline in a SAR image is a difficult task to perform partly because of the presence of speckle and partly because of similarity between the signal returned from the sea surface and that from the exposed tidal flat surface or land. Waterlines in SAR intensity and coherence map can effectively be extracted with MSP-RoA edge detector. From multiple images obtained over a range of tide elevation, it is possible to build up a set of heighted waterline within intertidal zone, and then a gridded DEM can be interpolated. We have tested the proposed method over the Gomso Bay, and succeeded in generating intertidal DEM with relatively high accuracy.