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RF magnetron sputtering으로 제조된 강 유전체 $SrBi_2Ta_2O_9$ 박막의 열처리 온도에 따른 특성 연구
박상식,양철훈,윤순길,안준형,김호기 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.2
Bi층 SrBi2Ta2O9(SBT)박막을 상온에서 rf magnetron sputtering에 의해 Pt/Ti/SiO2/Si기판위에 증착한 다음 산소 분위기 하에서 1시간동안 75$0^{\circ}C$, 80$0^{\circ}C$, 85$0^{\circ}C$로 열처리하였다. 타겟은 박막내의 Bi와 Sr의 부족을 보상하기 위해 20mole%의 Bi2O3와 30mole%의 SrCO3를 과잉으로 넣어 사용하였으며, 80$0^{\circ}C$로 열처리한 박막의 조성은 Sr0.7Bi2.0Ta2.0O9.0이었다. 200nm의 두께를 갖는 이 SBT박막은 치밀한 미세구조와, 1MHz의 주파수에서 210의 유전상수, 0.05의 유전손실을 나타내었고, 또한 100 kMz에서 32$0^{\circ}C$의 큐리온도를 나타냈으며 그 온도에서의 유전상수는 314이었다. 이 SBT박막의 잔류분극(2Pr)과 항전계(2Ec)값은 각각 인가전압 3V에서 9.1$\mu$C/$\textrm{cm}^2$과 85kV/cm이었고, 5V의 bipolar pulse 하에서 1010 cycle까지 피로현상이 나타나지 않았으며, 누설전류 밀도는 150kV/cm에서 7$\times$10-7A/$\textrm{cm}^2$의 값을 보였다. rf magnetron sputtering 으로 제조된 SBT박막은 비휘발성 메모리 소자에의 응용이 가능하다. Bi-layered SrBi2Ta2O9(SBT) films were deposited on Pt/Ti/SiO2/Si sibstrates by rf magnetron sputt-ering at room temperature and then were annealed at 75$0^{\circ}C$, 80$0^{\circ}C$ and 85$0^{\circ}C$ for 1 hour in oxygen at-mosphere. The film composition of SrBi2Ta2O9 was obtained after depositing at room temperature and annealing at 80$0^{\circ}C$. Excess 20mole% Bi2O3 and 30 mole% SrCO3 were added to the target to compensate for the lack of Bi and Sr in SBT film. 200 nm thick SBT film exhibited and dense microstructure, adielectric constant of 210, and a dissipation factor of 0.05 at 1 MHz frequency. The films exhibited Curie temperature of 32$0^{\circ}C$ and a dielectric constant of 314 at that temperature under 100 kHz frequency. The remanent polarization(2Pr) and the coercive field(2Ec) of the SBT films were 9.1 $\mu$C/$\textrm{cm}^2$ and 85 kV/cm at an applied voltage of 3V, resspectively and the SBT film showed a fatigue-free characteristics up to 1010 cy-cles under 5V bipolar pulse. The leakage current density of the SBT film was about 7$\times$10-7A/$\textrm{cm}^2$ at 150 kV/cm. Fatigue-free SBT films prepared by rf magnetron sputtering can be suitable for application to non-volatile memory device.
박상식,강부식 한국방재학회 2014 한국방재학회논문집 Vol.14 No.5
Recently, the increased high-risk weather events have caused more frequent threats of natural disasters, e.g. inundations, floods, landslides and infrastructure damages. In addition even equivalent strength of severe weather events could result in varied physical damagesand associated economic losses. In this study, the natural disaster Hazard Index (H-Index) was developed for evaluating regionaldisaster prevention capacity consisting of 10 detail indices, e.g. provision of sewage network, river improvement ratio, imperviousarea ration, etc., classified by vulnerability and risk categories. The weights for the H-index components were estimated using questionnairesurvey and entropy scheme. The final differentiating framework for regional storm warning criteria was suggested consideringAntecedent soil Moisture Condition (AMC) and differentiation coefficients associated with regionally varied reference storm scales. 최근 위험기상 발생빈도가 증가하여 홍수, 침수, 산사태나 기반시설 붕괴 등의 자연재해 위협이 증가하고 있다. 또한, 동일한 규모의 기상현상에 대해서도 도시화, 방재인프라, 선행강우 등 다양한 요소에 따라 물리적 피해 및 재산손실정도가 지역별로 다르게 나타나고있다. 이에 위험성 및 취약성 범주로 분류되어 하수관거보급율, 하천개수율, 불투수면적비 등 10개 세부지표으로 구성된 자연재난위험지수(Hazard-Index)를 개발하였고 지표항목들 간의 가중치를 설문조사와 엔트로피 기법으로 설정하였으며, 선행토양함수조건(AMC)및 지역별 강수변화를 고려한 특보차등화계수(α)를 활용한 지역별 호우특보기준 차등화 방안을 제시하였다.
박상식,신범재,우형수 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.2
The technology and market size of image sensors continue to develop thanks to the release of image sensors that exceed 100 million pixels in 2019 and expansion of black box camera markets for vehicles in addition to existing mobile applications. We review the technology flow of image sensors that have been constantly evolving for 40 years since Hitachi launched a 200,000-pixel image sensor in 1979. Although CCD has made inroads into image sensor market for a while based on good picture quality, CMOS image sensor (CIS) with active pixels has made inroads into the market as semiconductor technology continues to develop, since the electrons generated by the incident light are converted to the electric signals in the pixel, and the power consumption is low. CIS image sensors with superior characteristics such as high resolution, high sensitivity, low power consumption, low noise and vivid color continue to be released as the new technologies are incorporated. At present, new types of structures such as Backside Illumination and Isolation Cell have been adopted, with better sensitivity and high S/N ratio. In the future, new photoconductive materials are expected to be adopted as a light absorption part in place of the pn junction.