• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.3
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• pp.314-319
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• 2015

Invar is a compound metal of Fe-Ni system contained 36.5% Ni. The characteristic of invar is that the coefficient of thermal expansion is $1.0{\times}10^{-6}cm/^{\circ}C$. It is approximately 10 times smaller than series of steel. Because of this low thermal expansion characteristic of Invar, it is used to shadow mask of display device such as UHDTV or OLED TV. In this study, pulse current from pulse generator instead of DC current is used to overcome the disadvantages of the conventional electrochemical machining. Pulsed current with different duty factor in PECM affect the precise geometry. Pulse electrochemical machining is conducted to machine the micro hole to the invar sheet with different duty factor. The machined shape and overcut of invar sheet with different duty factor is observed by optical microscope and scanning electron microscope (SEM).

• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.235-238
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• 2005

A Multiple electron beam lithography system with arrayed microcolumns has been developed for high throughput applications. The small size of the microcolumn opens the possibility for arrayed operation on a scale commensurate. The arrayed microcolumns based on of Single Column Module (SCM) concept has been fabricated and successfully demonstrated. Low energy microcolumn lithography has been operated in the energy range from 250 eV to 300 eV for the generation of nano patterns. Probe beam current at the sample was measured about >1 nA at a total beam current of $0.5\;{\mu}A$ and a working distance of $\~1\;mm$. The magnitude of probe beam current is strong enough for the low energy lithography. The thin layers of PMMA resist have been employed. The results of nano-patterning by low energy microcolumn lithography will be discussed.

• Journal of the Korean Ceramic Society
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• v.20 no.4
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• pp.333-339
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• 1983

Semiconducting glaxe of iron system for the recent use as high Voltage porcelain insulators often showed the tendancy of unstable thermal properties. Thus the development of frit including magnetite was studied to cover the defect. In the experimental process melted and quenched frits were ground pelletized and heat-treated at various temperatures in the range of 800-1 $300^{\circ}C$ for various soaking time within 4 hours and then crystallized specimens were obtained. The speciment were studied with optical and electron microscope DTA x-ray diffractometer and electrometer The results obtained were as follows : 1) The optimum condition for the crystal growth of magnetite in the frite was the heat-treatment of $1300^{\circ}C$ for 3hrs and in this case the range of crystal size was $10-11\mu\textrm{m}$ 2) The activation energy for the crystal growth of magnetite was 21.1 kcal/mole. 3) The heat-treament at $1, 250^{\circ}C$ and $1, 300^{\circ}C$ resulted in the good thermal stability and the range of surface resistivity was $3.5{\times}10^4-4.0{\times}10^7$, /TEX> $\Omega$/$cm^2$ which was adguate to semiconducting frit. 4) The conduction mechanism seems to be due to the electron mobility rather than ion mobility and the activa-tion energy for the conduction was 0.07-0.15eV/mole for the heat-treated specimes in the range of 1, 250-1, 300C

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.29-32
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• 2010

In this study, transparent and conductive Al-doped zinc oxide (AZO) films were prepared on a glass substrate by an radio frequency (RF) magnetron sputtering method using a 150-nm-thick AZO target (Al: 2 wt.%) at room temperature. We investigated the effects of RF power between 100-350 W (in steps of 50 W) on the structural, electrical, and optical properties of the AZO films. The thickness and cross-sectional images of the films were observed by field emission scanning electron microscopy. The thicknesses of all films were kept constant at 150 nm and grown on a glass substrate. The grain sizes of the AZO films were determined with the X-ray diffraction by using the Scherrer' equation, and their electrical properties were investigated using a Hall effect electronic transport measurement system. The transmittance of the AZO films was also measured by an ultraviolet-visible spectrometer.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.458-464
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• 2006

The construction and the performance test of an ultra high vacuum (UHV) molecular beam epitaxy (MBE) system has been completed successfully. We have done domestic development and tried performance test for ultra high vacuum molecular beam epitaxy system. This system has reached pressure $2X10-^{10}$ Torr and the substrate has reached temperature $1,100^{\circ}C$. We have investigated into the characteristic of ZnSe/GaAs(001) by using scanning electron microscope (SEM), atomic force microscope (AFM), x-ray diffraction (XRD) and photolumi-nescence (PL).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.438-443
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• 2005

Laser surface hardening is an effective technique used to improve the tribological properties and also to increase the service life of automobile components such as camshafts, crankshatfs, lorry brake drums and gears. High power CO2 lasers and Nd:YAG lasers are employed for localized hardening of materials and hence are of potential application in the automobile industries. The heat is conducted rapidly into the bulk of the specimen causing self-quenching to occur and the formation of martensitic structure. In this investigation, the microstructure features occurring in Nd:YAG laser hardening SM45C steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimism of the processing parameters for maximum hardened depth of SM45C steel specimens of 3mm thickness by using CW Nd:YAG laser. Travel speed was varied from 0.6m/min to 1.0m/min. The maximum hardness and case depth fo SM45C steel are 780Hv and 0.4mm by laser hardening.

• Biomedical Science Letters
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• v.12 no.3
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• pp.177-183
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• 2006

To demonstrate the effect of formulation conditions and evaluations of structural integrity from ovalbumin containing poly lactide glycolide copolymer (PLGA) microspheres for Vaccine delivery, OVA microspheres were prepared by a W/O/W multiple emulsion solvent extraction technique. Dichloromethan (DCM) and Ethyl acetate (EA) were applied as an organic phase and poly vinyl alcohol (PVA) as a secondary emulsion stabilizer. Microspheres were characterized for particle size, morphology (optical microscopy and Scanning Electron Microscope (SEM)). Protein denaturation was evaluated by size exclusion chromatography (SEC), SDS-PAGE and isoelectric focusing (IEF). Residual organic solvent was estimated by gas chromatography (GC) and differential scanning calorimetry (DSC). Optical photomicrograph and SEM revealed that micro spheres were typically spherical but various morphologies were observed. Mean particle size $(d_{vs})$ of microspheres were in the range of $3{\sim}50{\mu}m$. Also, The protein stability was not affected by the fonnulation process and residual organic solvent was beyond the detection below 0.1ppm. These results demonstrated that micro spheres might be a good candidate for the parenteral vaccine delivery system.

• Journal of the Korean institute of surface engineering
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• v.47 no.4
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• pp.181-185
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• 2014

We investigated the structural, electrical and optical characteristics of IGZO thin films deposited by a room-temperature RF reactive magnetron sputtering. The thin films deposited were annealed for 2 hours at various temperatures of 300, 400, 500 and $600^{\circ}C$ and analyzed by using X-ray diffractometer, transmission electron microscopy, atomic force microscope and Hall effects measurement system. The films annealed at $600^{\circ}C$ were found to be crystallized and their surface roughness was decreased from 0.73 nm to 0.67 nm. According to XPS measurements, concentration of oxygen vacancies were decreased at $600^{\circ}C$. Optical band gap were increased to 3.31eV. The carrier concentration and Hall mobility were sharply increased at 600oC. Our results indicate that the IGZO films deposited at a room temperature can show better thin film properties through a heat treatment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1016-1020
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• 2002

Ru thin films were etched using CF/$_4$O$_2$ plasma in an ICP (inductively coupled plasma etching) system. The maximum etch rate of Ru thin films was 168 nm/min at a CF$_4$/O$_2$ gas mixing ratio of 10 %. The selectivity of SiO$_2$ over Ru was 1.3. From the OES (optical emission spectroscopy) analysis, the optical emission intensity of the O radical had a maximum value at 10% CF$_4$ gas concentration and drcrease with further addition of CF4 gas, but etch slope was enhanced. From XPS (x-ray photoelectron spectroscopy) analysis, the surface of the etched Ru thin film in CF$_4$/O$_2$ chemistry shows Ru-F bonds by the chemical reaction of Ru and F. RuF$_{x}$ compounds were suggested as a surface passivation layer that reduces the chemical reactions between Ru and O radicals. From a FE-SEM (field emission scanning electron microscope) micrograph, we had an almost perpendicular taper angle of 89$^{\circ}$.>.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.101-107
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• 2018

Li-incorporated ZnO thin films were deposited by using ultrasonic-assisted spray pyrolysis deposition (SPD) system. To investigate the effect of Li-incorporation on the performance of ZnO thin films, the structural, electrical, and optical properites of the ZnO thin films were analyzed by means of X-ray diffraction (XRD), field-emssion scanning electron microscopy (FE-SEM), Hall effect measurement, and UV-Vis spectrophotometry with variation of the Li concentraion in the ZnO sources. Without incorporation of Li element, the ZnO surface showed large spiral domains. As the Li content increases, the size of spiral domains decreased gradually, and finally formed mixed small grain and one-dimensional nanorod-like structures on the surface. This morphological evolution was explained based on an anti-surfactant effect of Li atoms on the ZnO growth surface. In addition, the Li-incorporation changed the optical and electrical properties of the ZnO thin films by modifying the crystalline defect structures by doping effects.