• 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.

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.

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.

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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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.

Development of experimental equipment for CVD processing model (CVD 공정모델 실험장치의 개발)

  • 정상범
    • Proceedings of the Korea Society for Simulation Conference
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    • pp.142-147
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    • 2000
  • 본 연구의 주안점을 실험용 CVD 장치의 CVD 반응기 내에 투입된 기체의 농도와 온도를 즉시 측정하여 새로운 소자 개발 시에 공정모델 수립과 정밀도를 요하는 공정에서 증착량과 속도에 대한 데이터를 구하므로써 효율적인 CVD 장치를 구성하는 것으로서 실험실이나 연구소에서 정확한 CVD 공정모델 실험을 할 수 있게 하여 새로운 소자의 시뮬레이션 모델을 만들 수 있는 효과적인 성장방법의 개발을 통하여 원료기체의 효율적인 사용이 이루어지도록 반응기내에서 가스 및 온도제어 시스템을 개발하였다.

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The improvement of characteristics for hydrogenated amorphous silicon thin films by photo-induced CVD (광 CVD에 의한 비정질 실리콘 박막 특성 향상)

  • 김용상;이성규;전명철;박진석;한민구
    • Electrical & Electronic Materials
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    • v.7 no.2
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    • pp.94-99
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    • 1994
  • The purpose of this work is to investigate the interface characteristics of hydrogenated amorphous silicon thin films prepared by PECVD and photo-induced CVD and to examine the annealing effects of ultraviolet irradiation on hydrogenated amorphous silicon thin films which were degraded by visible light illumination. The interface layer thickness of films deposited by photo-induced CVD was about 600-900.angs. while that by PECVD was about 1000-1300.angs.. These results can show that the quality of interface layer in photo induced CVD film is better than that in PECVD sample. The electrical properties are improved by ultraviolet irradiation on visible light soaked a-Si:H films using photo-CVD light sources, probably due to the fact that UV generates phonons in a-Si:H films and anneal the meta stable defects.

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A Meta-analysis on the Risk Factors of Cerebrovascular Disorders in Koreans (한국인 뇌혈관질환의 위험요인에 관한 메타분석)

  • Park, Jong-Ku;Kang, Myung-Guen;Kim, Chun-Bae;Kim, Ki-Soon;Jee, Sun-Ha
    • Journal of Preventive Medicine and Public Health
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    • v.31 no.1
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    • pp.27-48
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    • 1998
  • This study was conducted to integrate the results of studies which evaluated or identified the risk factors of CVD(cerebrovascular disorders) for Koreans. We retrieved the literature published in Korean by manual search and the English literature by Medline database to identify studies on the relationship between reported risk factors and CVD conducted for the Korean from 1980 to August, 1997. Hypertension and total serum cholesterol were selected as subjects of quantitative meta-analysis on risk factors of CVD in Koreans. The overall effect sizes of the risk of CVD due to hypertension and total serum cholesterol were calculated by common odds ratio(OR) and average standardized mean difference, retrospectively. Before the integration of each effect sizes into common effect sizes, the heterogeneity tests were conducted. Also, sensitivity tests were conducted for the estimated common effect sizes. Regarding hypertension and CVD, a total of 9 epidemiologic studies were identified with a total of 2,271 cases of CVD. The overall OR of hypertension associated CVD was 4.10(95% confidence interval[CI] 3.56 to 4.71). The OR of hypertension associated with hemorrhagic CVD and ischemic CVD were 6.56(95% CI : 4.92 to 8.80) and 3.28 (95% CI : 2.77 to 3.90), retrospectively. The OR of hypertension in relation to hemorrhagic CVD was significantly higher than that of hypertension in relation to overall CVD or ischemic CVD. Regarding total serum cholesterol and ischemic CVD, total 9 epidemiologic studies were identified with a total of 843 cases of ischemic CVD. Average mean difference as an effect size was 0.76, which was judged an important value according to Cohen's criteria. Our data suggested that hypertension was an important risk factor of overall CVD and its subtypes, and that the total serum cholesterol was associated with ischemic CVD in Koreans. For the lack of reliable prospective studies, however, we concluded that further research designed longitudinally would be required in this area.

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Integration of Chemical Vapor Deposition and Physical Vapor Deposition for the Al Interconnect (Al 배선 형성을 위한 화학증착법과 물리증착법의 조합 공정에 관한 연구)

  • 이원준;김운중;나사균;이연승
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.101-101
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    • 2003
  • Al 박막의 화학증착(CVD)과 Al-Cu 합금박막의 물리증착(PVD)을 조합하는 CVD-PVD Al 공정은 수평방향의 배선과 수직방향의 via를 동시에 형성할 수 있으므로 공정단순화 및 생산원가절감 측면에서 장점이 있어서 DRAM 둥의 반도체 소자의 배선공정으로 매우 유망하다[1]. 본 연구에서는 CVD-PVD Al 공정을 이용하여 초고집적소자의 Al via와 Al 배선을 동시에 형성할 때 층간절연막의 영향을 조사하고 그 원인을 규명하였다. Al CVD를 위한 원료기체로는 dimethylaluminum hydride [($CH_3$)$_2$AlH]를 사용하였고 PVD는 38$0^{\circ}C$에서 실시하였다 층간절연막에 따른 CVD-PVD Al의 via hole 매립특성을 조사한 결과, high-density plasma(HDP) CVD oxide의 경우에는 via hole 매립특성이 우수하였으나, hydrogen silscsquioxane (HSQ)의 경우에는 매립특성이 우수하지 않아서 via 저항이 불균일 하였다. 이는 via 식각 후 wet cleaning 과정에서 HSQ에 흡수된 수분이 lamp를 이용한 degassing 공정에 의해서 완전히 제거되지 않아 CVD-PVD 공정 중에 탈착되어 Al reflow에 나쁜 영향을 미치기 때문으로 판단된다. CVD-PVD 공정 전에 40$0^{\circ}C$, $N_2$ 분위기에서 baking하여 HSQ 내의 수분을 충분히 제거함으로써 via 매립특성을 향상시킬 수 있었다. CVD-PVD Al 공정은 aspect ratio 10:1 이상의 via hole도 완벽하게 매립할 수 있었고 이에의해 제조된 Al 배선은 기존의 W plug 공정에 의해 제조된 배선에 비해 낮은 via 저항을 나타내었다.

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