• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.1
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• pp.10-15
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• 2005

Effects of CH₄/H₂ flow rate ratio, chuck bias and microwave power on the structural properties and particle densities of diamond thin films deposited on Ti substrates in microwave plasma CVD were examined. High quality diamond thin films were deposited on Ti substrates in 2∼3 CH₄ Vol.% conditions due to the preferential formation of sp³-bonus ana selective removal of sp²-bonus in the CH₄/H₂ mixtures, and the mechanism for the formation of diamond particles on Ti was analysed. Diamond particle density increased with increasing negative chuck bias to Ti substrate due to bias-enhanced nucleation of diamond and the threshold voltage was found at ∼-50 V. With increasing microwave power the evolution from micro-crystalline graphite layer to diamond layer was observed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.240-248
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• 1998

The plasma chemical vapor deposition is one of the most utilized techniques for the diamond growth. As the applications of diamond thin films prepared by plasma chemical vapor deposition(CVD) techniques become more demanding, improved fine-tuning and control of the process are required. The important parameters in diamond film deposition include the substrate temperature, $CH_4/H_2$ gas flow ratio, total, gas pressure, and gas excitation power. With the spectroscopic ellipsometry, the substrate temperature as well as the various parameters of the film can be determined without the physical contact and the destructiveness under the extreme environment associated with the diamond film deposition. It is introduced how the real-time spectroscopic ellipsometry is used and the data are analyzed with the view of getting the growth condition and the accompanied features for a good quality of diamond films. And it is determined the important parameters during the diamond film growth, which include the final sample will be measured with Raman spectroscopy to confirm the diamond component included in the film.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.4
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• pp.149-153
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• 2017

Recently, significant amounts of gem-quality colorless HPHT synthetic melee diamond have produced for the jewelry industry. Consequently, there have been reports of cases of fraud in the world diamond business. For example, intentionally selling synthetic diamond as natural diamond or intentionally mixing a natural diamond parcel with a synthetic. As a result, the separation of natural from synthetic melee diamonds has become increasingly critical. At present, 10,000 cubic hinge presses are used for the production of synthetic diamond in China. From among these, reportedly 1,000 presses are used for gem-quality diamond production. One press can produce up to 10ct melee-size diamonds in 24 hours. Randomly occurring pinpoint or flux-metal inclusions are diagnostic identification clues. However, some synthetic diamonds require advanced laboratory method for identification. In order to ensure consumer confidence, it is essential to screen melees so as to distinguish all synthetic goods.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.227-232
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• 1998

Diamond crystallization and discontinuous deposit phenomena depend on the process of hydrocarbon deposition, nucleation and growth. Then, it is investigated the concentration of methane, flow rate, structure and the growth process of $CH_4-H_2$ system in hot filament assisted C.V.D. There is a limited value of temperature, pressure, flow rate and the mole fraction of methane-hydrogen gas. Diamond nucleation occurs on substrate selectively and surface diffusion of species on the substrate plays an important role in the early stages of nucleation and growth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.538-541
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• 2003

Ultra-precision machining was carried out on a electroless nickel materials using single crystal diamond tools. The effects of the cutting velocity, the tool length, the tool nose radius, the feed rate and depth of cut on the surface roughness were studied. In this paper, the cutting condition for getting nano order smooth surface of electroless nickel have been examined experimentally by the ultra-precision machine and single crystal diamond tools. And also. the surface roughness was measured by the three dimension

• Transactions on Electrical and Electronic Materials
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• v.3 no.2
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• pp.1-5
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• 2002

Alignment effects for nematic liquid crystal (NLC) and electro-optical (EO) characteristics of the ion beam (IB) aligned twisted nematic (TN)-liquid crystal display (LCD) with oblique ion beam exposure on the diamond-like carbon (DLC) thin film surface were studied. A high pretilt angle of 3.5$^{\circ}$ in NLC by ion beam exposure on the DLC thin film layer can be measured. An excellent voltage-transmittance (V-T) curve of the ion beam aligned TN-LCD was observed with oblique ion beam exposure on the DLC thin film surface for 1 min. Also, a faster response time for the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min can be achieved.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.1
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• pp.27-32
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• 2004

The diamond-like carbon (DLC) films were deposited on the Si (100) wafer by a rf-PECVD method as a function of the mixture rate of methane-hydrogen gas and bias voltage. The bonding structure and mechanical properties of these deposited DLC films were investigated using FT-IR, Raman, and nano-indenter. The deposition rates of DLC films increased with increased flow rate of methane in the gas mixtures and increased bias voltage. The $sp^3/sp^2$ bonding ratio of carbon in thin film and the hardness increased with increasing flow rate of hydrogen in the gas mixtures and increasing bias voltage.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.910-911
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• 2006

We newly designed and manufactured a new arranging system for a three-dimensional artificial crystal of monosized micro particles. In this system, a robotic micro-manipulator accurately locates the spherical particle onto the lattice point, and subsequently fiber lasers micro-weld the contact points between the neighboring particles. Actually, one- and two-dimensional arrays were constructed using monosized tin particles with the diameter of 400 m. Moreover, due to optimization of the process parameters, we successfully constructed the artificial crystals of simple cubic and diamond structures. In particular, the diamond structure which can represent a large photonic band gap is expected to progress toward a practical photonic crystal device.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.39-44
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• 2019

This study renewed the 'RE_Double Diamond' design process on the importance that material selection should reflect the needs of the consumer as much as possible in product development. In addition, the provider-centered secondary stakeholder map process among existing double-diamond methodologies has been applied, and the selection of materials through communication between designers and engineers, including the construction of information focused on visualization.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.173-179
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• 2013

Even though a rough diamond shape is irregular and rugged, it is easy to be processed to make gem, shaped facets (table, crown, pavilion and girdle) were precisely treated because they influence on the evaluation of diamond grading. Those specifications suitable for the standard round brilliant cut diamond polishing were investigated and in 95 % statistical confidence interval, standard deviation, mean and acceptable tolerance were examined. According to these variables (size, angle, depth, and thickness) distribution, the frequency analysis of ratings and proportions were compared with each other. The correlation between each variables and the evidence of influence represented in proportion were determined by the regression analysis applying LSM (Least Square Method). In this research, it was recognized that table sizes of the diamond jewels and pavilion depth (in %) influence the rating decision and in particular, the depth of pavilion acting as the main factor of proportions, also plays an important role in optical phenomena.