• Transactions of Materials Processing
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• v.12 no.7
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• pp.623-630
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• 2003

Nanomachining process, static nanoplowing, is one of the most promising lithographic technologies in terms of the low cost of operation and variety of workable materials. In nanomachining process, chemical effects are more dominant factor compared with those by physical deformation or fracture. For example, during the nanoscratch on a silicon surface in the atmosphere, micro protuberances are formed due to the mechanochemical reaction between diamond tip and the surfaces. On the contrary, in case of chemically stable materials, such as ceramic or glass, surface protuberances are not formed. The purpose of this study is to understand effects of the mechanochemical reaction between tip and surfaces on deformation behaviors of hard-brittle materials. Nanometerscale elasoplastic deformation behavior of single crystal silicon (100) was characterized with micro protuberance phenomena, and compared with that of borosilicate (Pyrex glass 7740). In addition, effects of the silicon protuberances on nanoscratch test results were discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.291-295
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• 2013

Surface chemical modification via air and hydrogen heat treatment was found to relieve the aggregation of nanodiamond (ND) seed particles and lead to a significantly enhanced nucleation density for ultrananocrystalline diamond (UNCD) film growth. After heat treatment in air and hydrogen, modification of surface functionalities and increase in the zeta potential were observed. Mean size of the ND aggregates was also dramatically reduced from ${\sim}2{\mu}m$ to ~55 nm. Si surface seeded with ND particles heat-treated at $600^{\circ}C$ in hydrogen produced a much higher nucleation density of ${\sim}2.7{\times}10^{11}cm^{-2}$ compared to untreated ND seeds.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.3
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• pp.105-109
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• 2004

In this study, we analyzed the influences of appraising elements such as weight, color and clarity of natural diamonds on their value in the round brilliant cut diamonds. To analyze the influences of these elements on the value of diamonds, data were made from a Rapaport Diamond Report which is the most reliable source of diamond prices. As the result of this study, it is clearly understood that color and clarity equally influenced the value of diamonds as a whole, but there were some partial variations according to grades of both elements. That is, value of clarity was higher than that of color in higher-quality diamonds but value of clarity was lower than that of color in lower-quality diamonds. Also, value of diamonds were closely co-related by three main elements which were weight, color and clarity, but weight was the most influencing element on the value of natural diamonds.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.46-50
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• 2007

We have studied the nematic liquid crystal (NLC) alignment effects on a nitrogen-doped diamond-like carbon (NDLC) thin film layer with ion beam irradiation. The pretilt angle for NLC on the NDLC surface with ion beam exposure was observed below 1 degree. Also, we had the good LC alignment characteristics on the NDLC thin films with ion beam exposure of 1800 eV. In thermal stability experiments, the alignment defect of the NLC on the NDLC surface with ion beam irradiation above annealing temperature of $250^{\circ}C$ can be observed. Therefore, the good thermal stability and LC alignment for NLC by ion beam aligned NDLC thin films 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.21-26
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• 2004

Results from PL and Raman spectroscopic analyses of HPHT (high-pressure high-temperature) treated type IIa diamonds are presented, and these spectral characteristics are compared with those of untreated diamonds of similar color and type. We identify a number of significant changes by 325 nm He/Cd laser excitation. Several peaks are removed completely, including H4, H3 system in HPHT treated diamond. The N3 system, however, increased in emission. Also we can find the behaviour of the nitrogen-vacancy related center N-V centers at 575 and 637.1 nm, as observed with 514 nm Ar ion laser excitation. When these centers are present, the FWHM (full width at half maximum) of 637.1 nm luminescence intensities offers a potential means of separating HPHT-treated from untreated type IIa diamonds. The width of 637.1 nm $(N-V)^-$line measured at the position oi half the peak's height are determine to range from 19.8 to $32.1cm^{-1}$ for HPHT treated diamonds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.398-398
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• 2007

Most recently, the Liquid Crystal (LC) aligning capabilities achieved by ion beam exposure on the diamond-like carbon (DLC) thin film layer have been successfully studied. The DLC thin films have a high mechanical hardness, a high electrical resistance, optical transparency and chemical inertness. Nitrogen doped Diamond Like Carbon (NDLC) thin films exhibit properties similar to those of the DLC films and better thermal stability than the DLC films because C:N bonding in the NDLC film is stronger against thermal stress than C:H bonding in the DLC thin films. Moreover, our research group has already studied ion beam alignment method using the NDLC thin films. The nematic liquid crystal (NLC) alignment effects treated on the SiNx thin film layers using ion beam irradiation for three kinds of N rations was successfully studied for the first time. The SiNx thin film was deposited by plasma-enhanced chemical vapor deposition (PECVD) and used three kinds of N rations. In order to characterize the films, the atomic force microscopy (AFM) image was observed. The good LC aligning capabilities treated on the SiNx thin film with ion beam exposure for all N rations can be achieved. The low pretilt angles for a NLC treated on the SiNx thin film with ion beam irradiation were measure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.41-41
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• 2010

In this research, to study tungsten carbide alloy(Co 0.5%) ultra precision turning possibility that is used Glass Molding Press(GMP) using conventional (Rake angle $-25^{\circ}$) single crystal diamond bite observed machining surface condition, surface roughness($R_a$), diamond bite cutting edge after tungsten carbide alloy ultra precision turning. Suggested and designed optimum chamfer bite shape to suggest ultra precision optimum bite using Finite Element Analysis(FEM). After machining tungsten carbide alloy ultra precision turning using optimum chamfer bite and comparing with conventional bite machine result and studied optimum chamfer bite design inspection and also tungsten carbide ultra precision turning possibility for high temperature compression glass lens molding.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1571-1573
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• 2003

Diamond films including nanocystalline and graphite phase are grown by microwave plasma chemical vapor deposition using $N_2$ additives and negative substrate bias at growth step. The microstructure of the films is controlled by changing $N_2$ gas ratio and negative bias. Defects and grain boundaries between diamond and graphite are proposed to be crucial factors for forming the conducting path of electron emissions. The effect of growth parameters on the film microstructure are investigated by Raman spectroscopy and scanning electron microscopy(SEM). Electron emission characteristics are also examined in terms of the film growth conditions.

• Journal of the Mineralogical Society of Korea
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• v.9 no.1
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• pp.35-42
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• 1996

Polycrystalline ZrH2 in tetragonal crystal system has been compressed in a modified Bassett-type diamond anvil cell up to 36.0 GPa at room temperature. X-ray diffraction data did not indicate any phase transitions at the present pressure range. The pressure dependence of the a-axis, c-axis, c/a and molar volume of ZrH2 was determined at pressures up to 36.0 GPa. Assuming the pressure derivative of the bulk modulus (K0') to be 4.11 from an ultrasonic value on Zr, bulk modulus (K0) was determined to be 160Gpa by fitting the pressure-volume data to the Birch-Murnaghan equation of state. Same sample was heated at $500^{\circ}C$ at the pressure of 9.8 GPa in a modified Sung-type diamond anvil cell. Unloaded and quenched sample revealed that the original tetragonal structure transforms into a hexagonal structured phase with a zero-pressure molar volume change of ~115.5%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.726-730
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• 2002

Electro-optical (EO) performances of the ion beam (IB) aligned twisted-nematic (TN)-liquid crystal display (LCD) with ion beam exposure on the new diamond-like carbon (DLC) thin film surface were investigated. A good voltage-transmittance (V-T) curve of the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min was observed. Also, the fast response time of the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min can be achieved. Finally, the residual DC voltage of the ion beam aligned TN-LCD on the DLC thin film surface is almost the same as that of the rubbing aligned TN-LCD on a polyimide (Pl) surface.