• Korean Journal of Materials Research
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• v.6 no.8
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• pp.833-840
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• 1996

Diamond thin films were deposited on p-type (100) Si wafers using MPECVD. Prior to deposition, ultrasonic striking was done to improve density of nucleation sites with dimond powder of 40~$60\mu$m size. Then diamond thin films were deposited at $^900{\circ}C$, 40Torr and 1000W microwave power using ${CH}_{4}$ and ${H}_{2}$ gases. The purity, the morphology and the microstructur'e and microdefects of diamond thin films were characterized by Raman spectroscopy, SEM and TEM, repectively. In Raman spectroscopy the peaks of non-diamond phase increased as ${CH}_{4}$, concentration increased. In SEM, the morphology of diamond thin films varied from crystalline to cauliflower as ${CH}_{4}$, concentration increased. As ${CH}_{4}$ con centration increased, the density of defects increased, with most defects being {III} twin. ${MTP}_{5}$, were formed with five (II]) planes. As these (Ill) Planes were twinned, ${MTP}_{5}$, represented five-fold symmetry. ]n the interfaces, defects in diamond thin films fanned out from small regions implying nucleation sites.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.301-306
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• 2017

Wire electrical discharge machining (WEDM) process was evaluated to slice Silicon (Si) for various applications. Specifically, various Si workpieces with various resistances, such as single and multi crystalline Si bricks and wafers were used. As conventional slicing processes, such as slurry-on or diamond-on wire slicing, are based on mechanical abrasions between Si and abrasive, there is a limitation to decrease the wafer thickness as well as kerf-loss. Especially, when the wafer thickness is less than $150{\mu}m$, wafer breakage increases dramatically during the slicing process. Single crystalline P-type Si bricks and wafers were successively sliced with considerable slicing speed regardless of its growth direction. Also, typical defects, such as microcracks, craters, microholes, and debris, were introduced when Si was sliced by electrical discharge. Also, it was found that defect type is also dependent on resistance of Si. Consequently, this study confirmed the feasibility of slicing single crystalline Si by WEDM.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.225-229
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• 2011

Most of the silicon cutting methods using the multi-wire with the slurry injection have been used for wafers of the crystalline solar cell. But the productivity of slurry injection cutting type falls due to low cutting speeds. Also, the direct contact with the metal wire and silicon block increases the concentration of metallic impurities in the wafer's surface. In addition, the abrasive silicon carbide (SiC) generates pollutants. And production costs are rising because it does not re-use the worn wire. On the other hand, the productivity of the cutting method using the diamond coated wire is about 2 times faster than the slurry injection cutting type. Also, the continuous cutting using the used wire of low wear is possible. And this is a big advantage for reduced production costs. Therefore, the cutting method of the diamond coated wire is more efficient than the slurry injection cutting technique. In this study, each cutting type is analyzed using the surface characteristics of the solar wafer and will describe the effects of the manufacturing process of the solar cell. Finally, we will suggest improvement methods of the solar cell process for using the diamond cutting type wafer.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.104-108
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• 2003

COF(Coefficient Of Friction), AE(Acoustic Emission), micro-cracks and crystal structure of the single crystalline silicon were investigated according to the induced normal load during scratching test. Scratching tests were performed with the loading rate of 100 N/min and various scratching speeds of 1, 3, 6, 10 mm/min from 0 up to 30 N of the maximum normal load. In consequence, COF, AE and crack density were observed to increase with increasing normal load or increasing scratching speed. Phase transformations from the silicon diamond structure to other structures were observed in the scratched grooves for the slow scratching speeds using micro-Raman spectroscopy.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.82-88
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• 2009

Ultra-precision turning is highly needed to manufacture molds for precision lens. In this study, micro-turning combined with elliptical vibration cutting (EVC), which is known to enhance micro- machining quality, was investigated by installing a rotary stage into the micro-grooving machine. From machining experiments involving materials of copper, brass, and aluminum and single and poly crystalline diamond tools, it was found that EVC produced thinner and curlier chips and that better surface finish could be achieved, compared with conventional turning, owing to prohibition of formation of burrs and built-up edges. Therefore, we found EVC micro turning could be readily utilized to manufacture precision mold.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.147-152
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• 2002

A new theory of thin film growth was suggested, where charged clusters of nanometer size are generated in the gas phase and are a major flux for thin films. The existence of these hypothetical clusters was experimentally confirmed in the diamond and silicon CVD processes as well as in metal evaporation. These results imply new insights as to the microstructure control of thin films. Based on this new understanding, the low temperature deposition of crystalline and amorphous silicon can be approached systematically.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.114-119
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• 2005

This study has been carried out with the eight HPHT processed NOUV diamonds - two yellow, two yellowish green, two green and two orangy yellow color stones. The gemological properties of these diamonds included a highly saturated body color, graphitized fractures around the girdles, tension cracks around crystalline inclusions, long-wave UV with medium yellowish green to a very strong yellowish green luminescence, and short-wave UV with faint yellowish green to a strong yellowish green luminescence. Distinctive features of spectroscopic properties include absorption peaks at 415 nm and 503 nm a strong absorption band at $460{\sim}480nm$ and a H2 center at 986nm. Infrared spectra showed an absorption peak at $1344cm^{-1}$ (C center), which is the characteristics related to single substitutional nitrogen.

• International Journal of Precision Engineering and Manufacturing-Green Technology
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• v.5 no.5
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• pp.571-581
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• 2018

In the present study, monitoring of elliptical vibration cutting process by utilizing internal data in the ultrasonic elliptical vibration device without external sensors such as a dynamometer and displacement sensor is investigated. The internal data utilized here is the change of excitation frequency, i.e. resonant frequency of the device, voltages applied to the piezoelectric actuators composing the device, and electric currents flowing through the actuators. These internal data change automatically in the elliptical vibration control system in order to keep a constant elliptical vibration against the change of the cutting process. Correlativity between the process and the internal data is described by using a vibration model of ultrasonic elliptical vibration cutting and verified by several experiments, i.e. planing and mirror surface finishing of hardened die steel carried out with single crystalline diamond tools. As a result, it is proved that it is possible to estimate the elements of elliptical vibration cutting process, e.g. tool wear and machining load, which are important for stable cutting in such precision machining.

• Applied Microscopy
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• v.48 no.4
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• pp.126-127
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• 2018

Carbon has numerous allotropes and various crystalline forms with full dimensionalities such as diamond, graphite, fullerenes, and carbon nanotubes leading a wide range of applications. Since the emerge of graphene consisting of a single atomic layer of carbon atoms, a fabrication of all-carbon-based device with combination of one-, two-, and three-dimensional carbons has become a hot issue. Here, we introduce an ultimate one-dimensional carbon atomic chain. Carbon atomic chains were experimentally created by removing atoms from monolayer graphene sheet under electron beam inside transmission electron microscope (TEM). A series of TEM images demonstrate the dynamics of carbon atomic chains over time from the formation, transformation, and then breakage.

• Journal of the Mineralogical Society of Korea
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• v.16 no.2
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• pp.161-169
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• 2003

A phase transformation study on a synthetic amorphous diopside, $(Ca,Mg)SiO_3$has been carried out up to ∼30 GPa, and ∼$1000^{\circ}C$ using a diamond anvil cell and YAG laser heating system, respectively. A starting amorphous material shows a direct transition to cubic $(Ca,Mg)SiO_3$perovskite at high pressure, which contradicts to the crystalline diopside phase transformation sequence disproportionating into mixtures of the orthorhombic$ MgSiO_3$perovskite and the cubic $CaSiO_3$perovskite phases. This discrepancy might be due to the different starting materials as well as the temperature variations at each specific experiment performed. The present phase transfor mation sequence would modify the mineralogical assemblage in the Earth transition region and the lower mantle depending upon the pressure, temperature and the oxygen partial pressure.