• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1309-1310
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• 2006

High-purity and super-hard nano-polycrystalline diamond has been successfully synthesized by direct conversion from high-purity graphite under static pressures above 15 GPa and temperatures above $2300^{\circ}C$. This paper describes research findings on the formation mechanism of nano-structure and on the contributing factor leading to high hardness.

• Journal of the Korean institute of surface engineering
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• v.53 no.3
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• pp.109-115
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• 2020

In this study, polycrystalline diamond was synthesized by chemical vapor deposition (CVD). Diamond films were deposited on a-plane sapphire substrates while changing the concentration of methane for hydrogen (CH₄/H₂), and the concentrations of methane were 0.25, 0.5, 1, 2, 3 and 4 vol%, respectively. Crystallinity and nucleation density according to changes in methane concentration were investigated. At this time, the discharge power, vacuum pressure, and deposition time were kept constant. In order to deposit polycrystalline diamond, the sapphire substrate was etched with sulfuric acid and hydrogen peroxide (ratio 3:7), and the sapphire surface was polished for 30 minutes with 100 nm-sized nanodiamond particles. The deposited diamond thin film was analyzed by a scanning electron microscope (SEM), a Raman spectra, Atomic force microscope (AFM) and an X-ray diffractometer (XRD). By controlling the ratio of methane to hydrogen and performing appropriate pre-treatment conditions, a polycrystalline diamond thin film having excellent crystallinity and nucleation density was obtained.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.2
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• pp.75-80
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• 2021

The crystal grains of polycrystalline diamond vary depending on deposition conditions and growth thickness. The diamond thin film deposited by the CVD method has a very rough growth surface. On average, the surface roughness of a diamond thin film deposited by CVD is in the range of 1-100 um. However, the high surface roughness of diamond is unsuitable for application in industrial applications, so the surface roughness must be lowered. As the surface roughness decreases, the scattering of incident light is reduced, the heat conduction is improved, the mechanical surface friction coefficient can be lowered, and the transmittance can also be improved. In addition, diamond-coated cutting tools have the advantage of enabling ultra-precise machining. In this study, the surface roughness of diamond was improved by thermal diffusion reaction between diamond carbon atoms and ferrous metals at high temperature for diamond thin films deposited by MPCVD.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.239-244
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• 2021

Following Silicon Carbide, single crystal diamond continues to attract attention as a next-generation semiconductor substrate material. In addition to excellent physical properties, large area and productivity are very important for semiconductor substrate materials. Research on the increase in area and productivity of single crystal diamonds has been carried out using various devices such as HPHT (High Pressure High Temperature) and MPECVD (Microwave Plasma Enhanced Chemical Vapor Deposition). We hit the limits of growth rate and internal defects. However, HFCVD (Hot Filament Chemical Vapor Deposition) can be replaced due to the previous problem. In this study, HFCVD confirmed the distance between the substrate and the filament, the accompanying growth rate, the surface shape, and the Raman shift of the substrate after vapor deposition according to the vapor deposition temperature change. As a result, it was confirmed that the difference in the growth rate of the single crystal substrate due to the change in the vapor deposition temperature was gained up to 5 times, and that as the vapor deposition temperature increased, a large amount of polycrystalline diamond tended to be generated on the surface.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.5
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• pp.831-836
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• 2013

This study demonstrates the process of fabricating patterns using tribonanolithography (TNL),with laboratory-made micro polycrystalline diamond (PCD) tools that are attached to an atomic force microscope (AFM). The various patterns are easily fabricated using mechanical scratching, under various normal loads, using the PCD tool on single crystal silicon, which is the master mold for replication in this study. Then, polydimethylsiloxane (PDMS) replica molds are fabricated using precise pattern transfer processes. The transferred patterns show high dimensional accuracy as compared with those of TNL-processed silicon micro molds. TNL can reduce the need for high cost and complicated apparatuses required for conventional lithography methods. TNL shows great potential in that it allows for the rapid fabrication of duplicated patterns through simple mechanical micromachining on brittle sample surfaces.