• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.62-62
• /
• 1999

Carbon based materials have many attractive properties such as a wide band gap, a low electron affinity, and a high chemical and mechanical stability. Therefore, researches on the carbon-based materials as field emitters have been drawn extensively to enhance the field emission properties. Especially, diamond gives high current density, high current stability high thermal conductivity durable for high temperature operation, and low field emission behaviors, Among these properties understanding the origin of low field emission is a key factor for the application of diamond to a filed emitter and the verification of the emission site and its distribution of diamond is helpful to clarify the origin of low field emission from diamond There have been many investigations on the origin of low field emission behavior of diamond crystal or chemical vapor deposition (CVD) diamond films that is intentionally doped or not. However, the origin of the low field emission behavior and the consequent field emission mechanism is still not converged and those may be different between diamond crystal and CVD diamond films as well as the diamond that is doped or not. In addition, there have been no systematic studies on the dependence of nondiamond carbon on the spatial distribution of emission sites and its uniformity. Thus, clarifying a possible mechanism for the low field emission covering the diamond with various properties might be indeed a difficult work. On the other hand, it is believed that electron emission mechanisms of diamond are closely related to the emission sites and its distributions. In this context, it will be helpful to compare the spatial distribution of emission sites and field emission properties of the diamond films prepared by systematic variations of structural property. In this study, we have focused on an understanding of the field emission variations of structural property. In this study, we have focused on an understanding of the field emission mechanism for the CVD grown undoped polycrystalline diamond films with significantly different structural properties. The structural properties of the films were systematically modified by varying the CH4/H2 ratio and/or applying positive substrate bias examined. It was confirmed from the present study that the field emission characteristics are strongly dependent on the nondiamond carbon contents of the undoped polycrystalline diamond films, and a possible field emission mechanism for the undoped polycrystalline diamond films is suggested.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.416-421
• /
• 2003

To obtain the surface roughness with range from l0nm to In n need a ultra-Precision machine, cutting condition and the study of materials. And n have to also consider the chip and vibration of diamond tool during processing. In this paper, the cutting conditions for getting mirror surface of aluminum alloy have been examined experimentally by using ultra-precision turning and single crystal diamond tool. In generally, the cutting conditions have effect on the surface roughness in ultra-precision turning. The result of surface roughness was measured by the ZYGO New View 200.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.585-588
• /
• 2003

We have studied how rubbing direction affects generation of disclination line in transmissive microdisplay for $90^{\circ}$ twisted nematic (TN) mode with pixel size of $22.2{\mu}m$. The rubbing direction of bottom substrate is changed from $0^{\circ}$ to $-135^{\circ}$ with a decrease step of $45^{\circ}$, and the results show that the generation regions of the disclination line are of a smallest size in $-135^{\circ}$ direction. The results were the same although the pixel size decreased. Consequently, the use of proper rubbing direction of liquid crystal can help overcome the problems of low aperture ratio and low contrast ratio in transmissive-type microdisplays. In addition, the pretilt angle of initial liquid crystal is found to make an important contribution to generation of the disclination line.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.6
• /
• pp.1515-1522
• /
• 1990

Ultra precision cutting should be satisfied with two conditions of Mirror Like and shape grade, and especially Mirror Like depends on surface roughness. In this study, in order to develop Mirror Cutting for Al alloy, this was done with edge form of single crystal diamond tool divided into R type and S type. Surface roughness machined by S type tool is more satisfactory than by R type tool, being the lowest value of 13.8nm. In addition, Mirror surface can reach above 90% of reflection rate by both R type and S type tool, but machined surface by R type tool has much more fine fracture portions rather than by S type tool. Even though feed rate decreases from 5.mu.m to 1.mu.m, surface roughness doesn't show improvement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1995.11a
• /
• pp.269-272
• /
• 1995

As methane concentration was varietal, the textures of diamond films deposited on Si(100)substrate could be observed by XRD, SEM and Raman spectroscope. As a result, O$_2$plasma etching has been useful to observe microscopic structure of diamond films by SEM. The cross section of diamond films deposited on Si(100) substrate with 4% concentration of methane to hydrogen was a polycrystal like a pillar. The diamond crystal like a pillar has been oriented to (110) surface and the high quality diamond with FWHM of Raman spectra being 3.8cm$\^$-1/ has been grown. As time goes by deposition time, the preferred orientation increases.

• Electrical & Electronic Materials
• /
• v.9 no.3
• /
• pp.270-276
• /
• 1996

As methane concentration was varied, the textures of diamond films deposited on Si(100)substrate were observed by XRD,SEM and Raman spectroscope. As a result, $O_{2}$ plasma etching has been useful to observe microscopic structure of diamond films by SEM. The cross section of diamond films deposited on Si(100)substrate with 4% concentration of methane to hydrogen was a polycrystal like a pillar. The diamond crystal like a pillar has been oriented to (110)surface and the high quality diamond film with FWHM of Raman spectra being 3.8 $cm^{-1}$ / has been grown. As time goes by deposition time, the preferred orientation increases

• Proceedings of the KIEE Conference
• /
• 1998.11c
• /
• pp.786-788
• /
• 1998

Synthetic diamond films were deposited on pretreated silicon substrate in activated gas phase using RF plasma-assisted CVD. We investigated the influence of $O_2$ gas on facets of diamond crystal. In $H_2-CH_4-O_2$ gas mixture, the increase of oxygen concentration lead to well-faceted diamond particles and increasing crystallinity of diamond films. The deposited diamond films were analyzed by SEM, XRD, Raman spectroscopy.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.5
• /
• pp.77-83
• /
• 2022

A high-hardness tool material is required to reduce extreme abrasive wear when drilling carbon fiber reinforced plastic (CFRP). Single-crystal diamond is the hardest material in the world, but it is very expensive to be used as a cutting tool. Polycrystalline diamond (PCD) is a diamond grit fused at a high temperature and pressure, and diamond-like carbon (DLC) is an amorphous carbon with high hardness. This study compares DLC coatings and PCD inserts to conventional TiAlN-coated tungsten carbide drills. In fiberglass and carbon fiber reinforced polymer drilling, the tool wear of DLC-coated carbide was approximately half that of TiAlN-coated tools, and slight tool wear occurred in the case of PCD insert end drills.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.12 no.6
• /
• pp.317-322
• /
• 2002

We have studied the sawing sach as the round brilliant cut, cushion barion cut and marquise cut. Through this study, we could examined the rate of waste from the grinding work, and find a solution for many problems which could be derived from the grinding work. We could reduce the rate of waste by this study about sawing technique; 2.5 % for round brilliant cut, 2.5 % for cushion barion cut and 5.5 % for marquise cut.

• Journal of Korean Vacuum Science & Technology
• /
• v.5 no.1
• /
• pp.1-6
• /
• 2001

We measured the simultaneous, time-resolved spectra of photon emission, electron emission, and frictional force during the abrasion single crystal MgO with a diamond stylus in vacuum. phE and EE signal can be detected with millisecond resolution during the wear of a single crystal MgO substrate with a diamond stylus. The emissions and wear behavior are strong function of surface condition, load and stylus velocity. Measurement on annealed vs as-received material show that the luminescence is primarily due to deformation, and the electron emission is primarily due to fracture. These emissions provide insight into the processes responsible for catastrophic failure of ceramics in wear applications.