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Effect of Polarity on a SiC Crystal Grown on a SiC Dual-seed Crystal by Using the PVT Method
박종휘,이원재,양우성,정정영,이상일,박미선,신병철,여임규,은태희,Seung-Seok Lee,Myong-Chuel Chun 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.21
SiC crystal ingots were grown on 4H-SiC dual-seed crystals by using a physical vapor transport (PVT) technique, and SiC crystal wafers and cross sections sliced from the SiC ingot were systematically investigated to find the polarity dependence of the crystal polytype. The growth rate of the SiC crystal grown in this study was about 0.15 mm/hr. N-type 2-inch SiC crystals exhibiting 4H- and 6H-SiC polytypes were successfully fabricated on the C-face and the Si-face, respectively. As the growth of the SiC crystal ingot proceeded, the SiC crystal region grown on the C-face seed crystal was enlarged compared to the SiC crystal region grown on the Si-face seed crystal. The incorporation of nitrogen donors and the growth rate in the SiC crystals grown on the C-face seed crystal were be higher than those in SiC crystals grown on a Si-face crystal.
CMP 공정에서 슬러리와 웨이퍼 형상이 SiC 웨이퍼 표면품질에 미치는 영향
박종휘,양우성,정정영,이상일,박미선,이원재,김재육,이상돈,김지혜,Park, Jong-Hwi,Yang, Woo-Sung,Jung, Jung-Young,Lee, Sang-Il,Park, Mi-Seon,Lee, Won-Jae,Kim, Jae-Yuk,Lee, Sang-Don,Kim, Ji-Hye 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.4
The effect of slurry composition and wafer flatness on a material removal rate (MRR) and resulting surface roughness which are evaluation parameters to determine the CMP characteristics of the on-axis 6H-SiC substrate were systematically investigated. 2-inch SiC wafers were fabricated from the ingot grown by a conventional physical vapor transport (PVT) method were used for this study. The SiC substrate after the CMP process using slurry added oxidizers into slurry consisted of KOH-based colloidal silica and nano-size diamond particle exhibited the significant MRR value and a fine surface without any surface damages. SiC wafers with high bow value after the CMP process exhibited large variation in surface roughness value compared to wafer with low bow value. The CMPprocessed SiC wafer having a low bow value of 1im was observed to result in the Root-mean-square height (RMS) value of 2.747 A and the mean height (Ra) value of 2.147 A.
단계별 광중합 방식이 복합레진 수복물의 수축 응력과 변연 접합도에 미치는 영향
박종휘,이난영,이상호 大韓小兒齒科學會 2006 大韓小兒齒科學會誌 Vol.33 No.2
본 연구는 단계별 광중합 방법이 복합레진의 중합 및 수축 응력에 미치는 효과를 비교, 평가하고자 자연치를 대상으로 와동을 형성하고 할로겐 광중합기와 LED 광중합기의 통법에 의한 연속 조사 및 단계별 조사법으로 각각 복합레진을 중합시킨 후 수축 응력을 측정하고 주사전자현미경을 통해 수복물과 와동의 계면부에서 접착 상태를 관찰하여 다음과 같은 결과를 얻었다. 1. 모든 군에서 광중합 직후에는 일시적으로 팽창되었다가 초기에는 급격한 수축 응력의 증가를 보였고 시간이 경과될수록 수축 응력의 증가가 완만해지는 경향을 보였다(P<0.05). 2. 동일한 광조사 군내에서는 hybrid형인 Filtek Z-250™군보다는 flowable형인 Filtex flow™군이 더 적은 수축 응력을 보였다. 3. Filtek Z-250™군에서는 LED 단계별 조사군이 수축 응력이 가장 적게 나타났다.(P<0.05). 4. Filtek flow™군 역시 LED 단계별 조사군이 수축 응력이 가장 작게 나타났으나(P<005) Filtek Z-250군에서와 같이 다른 조사군에 비해 많은 차이를 보여주지는 못했다. 5. 주사전자현미경으로 관찰한 복합레진과 와동벽과의 접합 상태는 긴밀한 상태를 보였으나 LED 조사군에서 일부 틈이 관찰되었다. 이상의 결과를 종합해 보면 hybrid형 복합레진의 경우 단계별 중합방식을 사용할 경우 단일광도의 중합방식에 비해 수축응력을 감소시킬 수 있고 적절한 변연 적합상태를 유지시킴으로써 임상적으로 고광도 LED 광중합기의 경우 단계별 중합방식의 사용이 유리하다고 사료된다. The purpose of this study was to inverstigate the effect of step-curing mode on polymerization shrinkage and contraction of composite resion restoration. Class I cavities were prepared on the extracted human premolars. The cavities were filled with Filtek Z-250™(hybrid resin, 3M ESPE, USA) and Filtek flow™(flowable resin, 3M ESPE, USA) and cured with one of the following irradiation modes; Halogen 40sec with continuous curing, LED 10sec with continuous curing, and LED 13sec with step-curing. Contraction stress was measured with strain gauge which was connected to TML Datalogger™(TDS-102, SOKKI, Japan) and resion-dentin interfaces were observed by scanning electron microscope. The results of present study can be summarized as follows: 1. Composite resion restoration showed transient expansion just after irradiation of curing light. Contraction stress was increased rapidly at the early phase of polymerization and reduced slowly as time elapsed(P<0.05). 2. Filtek flow™ showed lower contraction stress than Filtek Z-250™ regardless of curing modes. 3. LED step-curing mode showed lowest contraction stress in Filtek Z-250™ compared with other curing modes(P<0.05). 4. LED step-curing mode showed lowest contraction stress in Filtek flow™ compared with other curing modes(P<0.05), but difference in contraction stress was not go greate as in Filtek Z-250™. 5. Polymerization of composite resion by LED light with step-curing mode and halogen light with continuous mode resulted in better marginal sealing than LED light with continuous mode.
탄화규소 단결정 성장 시 종자정 도핑농도 영향에 따른 결정 다형변화 연구
박종휘,양태경,이상일,정정영,박미선,이원재,Park, Jong-Hwi,Yang, Tae-Kyoung,Lee, Sang-Il,Jung, Jung-Young,Park, Mi-Seon,Lee, Won-Jae 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.10
In this study, SiC single-crystal ingots were prepared on two seed crystals with different doping level by using the physical vapor transport (PVT) technique; then, SiC crystal wafers sliced from the grown SiC ingot were systematically investigated to find the effect of seed doping level on the doping concentration and crystal quality of the SiC. To exclude extra effects induced by adjustment of the process parameters, we simultaneously grew the SiC crystals on two seed crystals with different level, which were fabricated from previous two SiC crystal ingots.