• Title, Summary, Keyword: CVD

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Mechanical Properties of CVD Diamond

  • Yoshikawa, Masanori;Hirata, Atsushi
    • The Korean Journal of Ceramics
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    • v.2 no.4
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    • pp.212-215
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    • 1996
  • This paper focuses the strength and wear resistance of CVD diamond films. The strength of free-standing CVD diamond films synthesized by microwave plasm CVD, DC plasma CVD, RF plasma CVD and arc discharge plasma jet CVD has been measured by three-point bending test. The wear resistance of CVD diamod films has been evaluated by the pin-on-disk type testing. diamond films coated on the base of sintered tungsten carbide pin by hot filament CVD have been rubbed with a sintered diamond disk in muddy water. Volume removed wear of CVD diamond has been compared with stellite, WC alloy and bearing steel.

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A comparative study of physical properties of $TiO_2$ thin films according to a coating method on orthodontic wires and brackets (교정용 와이어 및 브라켓에 이산화티탄 광촉매 코팅 시 코팅방법에 따른 비교연구)

  • Koh, Eun-Hee;Cho, Jin-Hyoung
    • The korean journal of orthodontics
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    • v.36 no.6
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    • pp.451-464
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    • 2006
  • The purpose of this study was to search for an appropriate method of coating $TiO_2$ on orthodontic appliances. $TiO_2$ thin films were deposited on orthodontic wires and brackets using sol-gel, CVD (Chemical Vapor Deposition) and PE-CVD (Plasma Enhanced-CVD) methods. The roughness of $TiO_2$-coated surfaces was investigated via scanning electron microscope (SEM) and adhesive strength of $TiO_2$ thin films was measured by adhesive tape pull test. Methylene blue degradation test was carried out to evaluate the photocatalytic activity of $TiO_2$ and the corrosion resistance of $TiO_2$ thin films against fluoride solution was also analyzed by observing the surfaces of $TiO_2$-coated wires and brackets via SEM after immersion in sodium fluoride solution. Through the comparison of properties and photocatalytic activity of $TiO_2$ thin films according to the coating methods, the following results were obtained. Smoother surfaces of $TiO_2$ thin films were generated by CVD or PE-CVD methods than through the sol-gel method or the control. Adhesive strength of the $TiO_2$ thin films was highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Photocatalytic activity of $TiO_2$ thin films on methylene blue was the highest in PE-CVD and gradually became lower in the order of CVD, then the sol-gel method. Corrosion resistance of $TiO_2$ thin films against fluoride solution was stronger in CVD and PE-CVD methods than in the sol-gel method. The results of this study suggest that the CVD or PE-CVD methods is more appropriate than the sol-gel method for $TiO_2$ coating on orthodontic wires and brackets.

Latchup characteristics of BL/BILLI retrograde twin well CMOS with MeV ion implanted Bored Layer (MeV 이온주입에 의한 매입층을 갖는 BILLI retrograde well과 latchup 특성)

  • Kim, Jong-Kwan;Kim, In-Soo;Kim, Young-Ho;Shin, Sang-Woo;Sung, Yung-Kwon
    • Proceedings of the KIEE Conference
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    • pp.1270-1273
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    • 1997
  • We have investigated the latchup characteristics of BL/BILLI retrograde twin well CMOS that has the high energy ion implanted buried layer to intend for more improvement of latchup compare to conventional retrograde well and BILLI structures. We explored the dependence of various latchup characteristics such as n+ trigger latchup and p+ trigger latchup on the buried layer implant doses. We show various DC latchup characteristics that allow us to evaluate each technology and suggest guidelines for the reduction of latchup susceptibility.

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A Study on Reducing High Energy Ion Implant Induced Defect (고에너지 이온주입 공정에 의한 유기 결함과 그 감소 대책)

  • Kim, Young-Ho;Kim, In-Soo;Kim, Chang-Duk;Kim, Jong-Kwan;Sung, Yung-Kwon
    • Proceedings of the KIEE Conference
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    • pp.1292-1297
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    • 1997
  • 본 연구에서는 latch-up 개선책의 일환으로 개발중인 매립층을 갖는 retrograde well의 형성기술과 더불어 공정 단순화를 목적으로 개발된 BILLI (Buried Implanted Layer for Lateral Isolation) well 구조[1]에 대한 공정 유기 결함을 분석하고 그에 의한 소자 열화 특성을 분석 하였으며 그 개선책을 제시 하고자 하였다. 매립층 형성에 의한 유기결함은 접합 누설전류와 Gate oxide 신뢰성을 열화 시켰으나 이온주입 후 $1000^{\circ}C$ 이상의 온도에서 10sec 정도의 RTP anneal에 의해 그 소자 특성이 개선되며 표면 결함이 감소함을 알 수 있었다.

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Properties of the Natural and CVD Synthetic Diamonds for Identification (천연과 CVD 합성 다이아몬드의 감별을 위한 물성 연구)

  • Kim, Yunwoo;Song, Jeongho;Noh, Yunyoung;Song, Ohsung
    • Journal of the Korean Ceramic Society
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    • v.51 no.4
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    • pp.350-356
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    • 2014
  • Recently, Chemical Vapor Deposition (CVD) synthetic diamonds have been introduced to the jewelry gem market, as CVD technology has been making considerable advances. Unfortunately, CVD diamonds are not distinguishable from natural diamonds when using the conventional gemological characterization method. Therefore, we need to develop a new identification method that is non-destructive, fast, and inexpensive. In our study, we employed optical microscopy and spectroscopy techniques, including Fourier transform infra-red (FT-IR), UV-VIS-NIR, photoluminescence (PL), micro Raman, and cathodoluminescent (CL) spectroscopy, to determine the differences between a natural diamond (0.30 cts) and a CVD diamond (0.43 cts). The identification of a CVD diamond was difficult when using standard gemological techniques, UV-VIS-NIR, or micro-Raman spectroscopy. However, a CVD diamond could be identified using a FT-IR by the Type II peaks. In addition, we identified a CVD diamond conclusively with the uneven UV fluorescent local bands, additional satellite PL peaks, longer phosphorescence life time, and uneven streaks in the CL images. Our results suggest that using FT-IR combined with UV fluorescent images, PL, and CL analysis might be an appropriate method for identifying CVD diamonds.

Swift Synthesis of CVD-graphene Utilizing Conduction Heat Transfer

  • Kim, Sang-Min;Mag-isa, Alexander E.;Oh, Chung-Seog;Kim, Kwang-Seop;Kim, Jae-Hyun;Lee, Hak-Joo;Yoon, Jonghyuk;Lee, Eun-Kyu;Lee, Seung-Mo
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.652-652
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    • 2013
  • The conventional thermal chemical vapor deposition (CVD) setup for the graphene synthesis has mainly used convective heat transfer in order to heat a catalyst (e.g. Cu) up to $1,000^{\circ}C$. Although the conventional CVD has been so far widely accepted as the most appropriate candidate enabling mass-production of high-quality graphene, this method has stillremained under the standard for the commercialization largely due to the poor productivity arisen out of the required long processing time. Here, we introduced a fast and efficient synthetic route toward CVD-graphene. Unlike the conventional CVD using convection heat transfer, we adopted a CVD setup utilizing conduction heat transfer between Cu catalyst and rapid heating source. The high thermal conductive nature of Cu and the employed rapid heating source led to the remarkable reduction in processing timeas compared to the conventional convection based CVD (Fig. 1A), moreover, the synthesized graphene was turned out to have comparable quality to that synthesized by the conventional CVD (Fig. 1B). For the optimization of the conduction based CVD process, the parametric studies were thoroughly performed using through Raman spectroscopy and electrical sheet resistance measurement. Our approach is thought to be worth considerable in order to enhance productivity of the CVD graphene in the industry.

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Low-resistance Transparent Plane Heating System using CVD Graphene (CVD 그래핀을 이용한 저저항 투명면상발열 시스템)

  • Yoo, Byongwook;Han, Sangsoo
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.12 no.3
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    • pp.218-223
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    • 2019
  • To prevent the low heating effect of heating system caused by the high sheet resistance of CVD graphene, multi-layered graphene was laminated to implement a Transparent plane heating system with good optical properties of low-resistance. Low-resistance plane heating system implemented by $300{\times}400{\times}5mm$ heating plane laminated multi-layered CVD graphene film and PWM control system to drive efficient power. A plane resistance value of $85.5{\Omega}/sq$ was measured on average for 4-layer CVD graphene film used as a heating plane. Thus, the transfer by thermal film as the method of implementing low-resistance CVD graphene is reasonable. The experimental results of heat test show that an average heat-rise rate in low-resistance, transperent plane heating system using CVD graphene is $10^{\circ}C/min$ and has an optical transmittance rate of 86.44%. Therefore, the proposed heating system is applicable to large window glass and vehicle heating window-shild-glass.

Factors Associated with Blue-collar Workers' Risk Perception of Cardiovascular Disease

  • Hwang, Won Ju;Hong, OiSaeng;Kim, Mi Ja
    • Journal of Korean Academy of Nursing
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    • v.42 no.7
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    • pp.1095-1104
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    • 2012
  • Purpose: The purpose of this study was to investigate the contribution of actual cardiovascular disease (CVD) risk, as well as, individual, psychosocial, and work-related factors as predictors of CVD risk perception among Korean blue-collar workers. Methods: The participants were 238 Korean blue-collar workers who worked in small companies. Data were collected through a survey; anthropometric and blood pressure measures; and blood sampling for lipid levels. Results: Blue-collar workers had high actual CVD risk and low CVD risk perception. The significant predictors of risk perception included perceived health status, alcohol consumption, knowledge of CVD risk, actual CVD risk, decision latitude, and shift work. The model explained 26% of the variance in CVD risk perception. Conclusion: The result suggests when occupational health nurses are giving routine health examination in small companies, they can enhance CVD risk perception in blue-collar workers by providing essential information about CVD risk factors and personal counseling on the individual worker's CVD risk status.

Electron field emission from various CVD diamond films

  • Usikubo, Koji;Sakamoto, Yukihiro;Takaya, Matsufumi
    • Journal of the Korean institute of surface engineering
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    • v.32 no.3
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    • pp.385-388
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    • 1999
  • Electron field emission properties from various CVD diamond films were studied. Diamond films were synthesized by microwave plasma CVD at 1173K and at 673K substrates temperature and pulse microwave plasma CVD at 1173K. B-doped diamond film was synthesized by microwave plasma CVD at 1173K also. Estimation by SEM, both the non-doped diamond film and B-doped diamond film which were synthesized at 1173K substrate temperature were $2~3\mu\textrm{m}$ in diameter and nucleation densities were $10^{8}{\;}numbers/\textrm{cm}^2$ order. The diamond film synthesized at 673K was $0.2\mu\textrm{m}$ in diameter and nucleation densities was 109 numbers/cm2 order. The diamond film synthesized by pulse microwave plasma CVD at 1173K was $0.2\mu\textrm{m}$ in diameter and nucleation density was $10^{9}{\;}numbers/\textrm{cm}^2$ order either. From the result of electron field emission measurement, electron field emission at $20V/\mu\textrm{m}$ from CVD diamond film synthesized by pulse microwave plasma CVD was $37.3\mu\textrm{A}/\textrm{cm}^2$ and the diamond film showed the best field emission property comparison with other CVD diamond.

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Glutathione S-transferase polymorphisms and traditional classification in Korean population with cerebrovascular disease

  • Um, Jae-Young;Ok, Yoon-Young;Joo, Jong-Cheon;Kim, Kyung-Yo;Kim, Na-Hyung;Hong, Seung-Heon;Kim, Hyung-Min
    • Oriental Pharmacy and Experimental Medicine
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    • v.4 no.2
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    • pp.112-119
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    • 2004
  • Glutathione S-transferase polymorphisms (GST) were examined in 98 cases with cerebrovascular disease (CVD) to test the hypothesis that GST polymorphisms confer a risk to an individual to develop CVD. Tobacco smoke is a major cause of both cancer and vascular disease. We therefore were stratified the subjects with CVD for smoking status, and then examined whether polymorphisms in this detoxification enzyme gene, GST, influence risk of CVD. Neither GSTM1 nor GSTT1 genotypes in the CVD group was significantly different from the control group (n=230), even in smokers. We attempted the combined analyses for GSTM1 and GSTT1 genotypes in CVD for smoking status. No significant association observed between the combined genotypes and CVD. We also classified the subjects and control group into four types according to Sasang Constitutional Medicine, Korean Traditional Oriental Medicine, and investigated the association among GST genotypes, CVD, and Sasang constitutional classification. Our observations do not confirm the effect of the GSTM1 and GSTT1 genotypes as a risk factor for CVD, even in smokers. Furthermore, we first attempted to evaluate the efficacy of Sasang Constitutional Medicine, and to find an association with CVD.