• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.200-205
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• 1995

The 1st and 2nd-order grating structure for long wavelength DFB(Distributed FeedBack) laser diodes are successfully fabricated on InP substrates by using electron beam lithography and reactive ion etch techniques, and also characterized non-destructively by diffraction analysis without removal of photo-resis layer. A new composite layer made by lifted-off Cr layer on thin SiO2 film is developed and used as an etch mask, because PMMA, the e-beamresist, is unsuitable for reactive ion etch of InP. In addition, it is experimentally confiremed that diffraction analysis makes it possible to predict the grating parameters, and the analysis can be used as a non-destructive on-line test to prevent incomplete gratings from being successively processed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.39-42
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• 2000

Cutrent technological development toward miniaturization requires smaller components. These components usually generate complex multi-DOF motions other than simple 1-DOF motlon. Therefore it is essential to develop measurement methodology for 6-DOF motions. In this paper, a new 6-DOF measurement system for milli-struchlre is presented. This methodology basically employs the Optical Beam Deflection Method (OBDM) with a diffraction grating. A laser beam is emitted toward the difliaction grating which could be attached on the surface of a milli-structue and the incident ray is dif'||'&'||'acted in several directions. Among these difliacted beams, $0^{th}$ and $\pm$ $1^{th}4" order difkicted rays are detected by 4 Quadrant Photodiodes. From coordinate values fram each detector, we can get information for 6-DOF motions with lineariration method, Required resolutions for milli-struchue measurement are suh-micrometer in translation and arcsec in rotation. Experimental results indicate that proposed system has possibility to satisfy this requirement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.757-761
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• 2001

In order to study noise barriers of complex shapes and to assess their efficiency, precise prediction model is required. For instance, geometrical approaches cannot deal with complex diffraction effects. So that in this paper, the time domain numerical computation method(Computational Aeroacoustics method) is applied to estimate noise reduction by diffraction and finite impedance condition. The CAA method can be used to calculate exactly the pressure of complex barrier shape with different impedance condition, such as T-shape, cylindrical edge and multi-edge noise barriers.

• Journal of the Semiconductor & Display Technology
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• v.5 no.1 s.14
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• pp.51-55
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• 2006

MgO thin films were prepared through electron-beam deposition onto ITO-coated glass substrates in order to measure electrical, dielectric, and microstructural properties. Design of experiments was performed in this study with the aim to understanding of the effects of processing variables, e.g., substrate temperature and filament current of an e-beam evaporator statistically. Leakage currents, relative dielectric constants, and diffraction intensities of MgO thin films were analyzed statistically, following the analysis procedure provided in the design of experiments. The leakage current level of MgO thin films has been found to be statistically significant at the level of $\alpha=0.1$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.246-250
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• 2001

ZnO thin films for light emission device have been deposited on sapphire and silicon substrates by pulsed laser deposition technique(PLD). A Nd:YAG laser was used with the wavelength of355 nm. In order to investigate the emission properties of ZnO thin films, Pl measurements with an Ar ion laser a light source using an excitation wavelength of 351 nm and a power of 100 mW are used. All spectra were taken at room temperature by using a grating spectrometer and a photomultiplier detector. ZnO exhibited Pl bands centers around 390, 510 and 640 nm, labeled near ultra-violet(UV), green and orange bands. Structural properties of ZnO thin films are analyzed with X-ray diffraction(XRD).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.781-785
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• 2000

Chalcogenide glasses are suggested as a candidate for optical recording. In this study, we have investigated the holography recording and reconstruction of the polarization state in chalcogenide As$_{40}$ Ge$_{10}$Se$_{15}$ S$_{35}$ thin films. We have used a He-Ne laser light(633nm) to probe and record of the grating. Also the polarization state of object beam was modulated with a λ/4 wave plate. The polarization state of the +1st order diffracted beam was generated by readout of the grating with a linearly polarized reference beam. It was the same-handed polarization state as the polarization state of the recording beam. The result is shown that the diffraction efficiency of circularly polarized recording represents higher than other polarization state.ate.e.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.25-26
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• 2006

The method measuring the absolute position of a point diffraction source emitting a spherical wavefront in three-dimension is proposed. Two-dimensional interference of spherical wavefronts is used to overcome ambiguity of phase order. The spherical wavefront is explicated by Taylor series expansion, from which a radius of curvature of a spherical wavefront and its center position in three-dimension are obtainable. The spherical wavefront is reconstructed by a modified lateral shearing interferometer, which uses single-mode fiber as a point diffraction source.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.418-422
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• 2005

In this study, the die design and die series on the surface residual stress of cold drawn eutectoid steel wire has been investigated. Test pieces were fabricated using die series with different mean and final reduction ratio. Surface residual stresses in the axial direction were measured by X-ray diffraction, Broker's 2-dimensional GADDS system. Results were compared with stress profiles which were calculated by 3D and 2D finite element simulation, Hibbitt's ABAQUS 6.4 program in Finite Element Analysis. By means of FEA method, optimal die shape considering delta-parameter were induced and applied in order to determine die sequence designs. Balance of the drawing stresses was also introduced to optimize die sequence.

• Transactions of Materials Processing
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• v.15 no.2 s.83
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• pp.153-157
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• 2006

In this study, the die design and die series on the surface residual stress of cold drawn eutectoid steel wire have been investigated. Test pieces were fabricated using die series with different mean and final reduction ratios. Surface residual stresses in the axial direction were measured by X-ray diffraction, Bruker's 2-dimensional GADDS system. The results were compared with stress profiles that were calculated by 3D and 2D finite element simulations, ABAQUS 6.4 program in finite element analysis(FEA). By means of the FEA method, optimal die shape considering delta-parameter were induced and applied in order to determine die sequence designs. Balance of the drawing stresses was also introduced to optimize die sequence.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1045-1052
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• 1997

Barium ferrites (BaFe12O19) were synthesized at the various temperature by the coprecipitation-oxidation method. X-ray diffraction Rietveld analysis for barium ferrites were performed, their microstructures were observed and their magnetic properties were measured, in order to analyze the crystal structures and determine the optimal temperature of heat-treatment. The barium ferrite, its average particle size 80 nm, was formed at 600℃ through the hematite (α-Fe2O3), but the site occupations of the Fe's in tetrahedral and bipyramidal sites and of the Ba relatively low. Increasing the heating temperature, these occupations and the magnetization increased, and the crystal c-axis decreased. These changes were very small at the heat treatment of above 800℃, but the particles were rapidly grown. It is suggested that the optimal temperature of heat-treatment is 800℃, at which temperature crystal structure is relatively stable and the particles hardly ever grow.