Ni/CNT/SiO2 구조의 4H-SiC MIS 캐패시터의 전기적 특성

이태섭,구상모,Lee, Taeseop,Koo, Sang-Mo 한국전기전자학회 2014 전기전자학회논문지 Vol.18 No.4

본 연구에서는, Ni/CNT/$SiO_2$ 구조의 4H-SiC MIS 캐패시터를 제작하고 전기적 특성을 조사하였다. 이를 통하여 4H-SiC MIS 소자에서 탄소나노튜브의 역할을 분석하고자 하였다. 탄소나노튜브는 이소프로필알코올과 혼합하여 $SiO_2$ 표면에 분산하였다. 소자의 전기적 특성 분석을 위하여 300-500K의 온도 범위에서 소자의 정전용량-전압 특성을 측정하였다. 밴드 평탄화 전압은 양의 방향으로 shift되었다. 정전용량-전압 그래프로부터 계면 포획 전하 밀도 및 산화막 포획 전하 밀도가 유도되었다. 산화막의 상태는 4H-SiC MIS 구조의 계면에서 전하 반송자 또는 결함 상태와 관련된다. 온도가 증가함에 따라 밴드 평탄화 전압은 음의 방향으로 shift되는 결과를 얻었다. 실험 결과로부터, Ni과 $SiO_2$ 계면에 탄소나노튜브를 첨가함에 따라 4H-SiC MIS 캐패시터의 게이트 특성을 조절 가능할 것으로 판단된다. In this study, the electrical characteristics of Ni/CNT/$SiO_2$ structures were investigated in order to analyze the mechanism of carbon nanotubes in 4H-SiC MIS device structures. We fabricated 4H-SiC MIS capacitors with or without carbon nanotubes. Carbon nanotubes were dispersed by isopropyl alcohol. The capacitance-voltage (C-V) is characterized at 300 to 500K. The experimental flat-band voltage ($V_{FB}$) shift was positive. Near-interface trapped charge density and oxide trapped charge density values of Ni/CNT/$SiO_2$ structure were less than values of reference samples. With increasing temperature, the flat-band voltage was negative. It has been found that its oxide quality is related to charge carriers or defect states in the interface of 4H-SiC MIS capacitors. Gate characteristics of 4H-SiC MIS capacitors can be controlled by carbon nanotubes between Ni and $SiO_2$.

탄소나노튜브를 첨가한 4H-SiC MOS 캐패시터의 전기적 특성

이태섭,구상모,Lee, Taeseop,Koo, Sang-Mo 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.9

In this study, the electrical characteristics of the nickel (Ni)/carbon nanotube (CNT)/$SiO_2$ structures were investigated in order to analyze the mechanism of CNT in MOS device structures. We fabricated 4H-SiC MOS capacitors with or without CNTs. CNT was dispersed by isopropyl alcohol. The capacitance-voltage (C-V) and current-voltage (I-V) are characterized. Both devices were measured by Keithley 4200 SCS. The experimental flatband voltage ($V_{FB}$) shift was positive. Near-interface trap charge density ($N_{it}$) and negative oxide trap charge density ($N_{ox}$) value of CNT embedded MOS capacitors was less than that values of reference samples. Also, the leakage current of CNT embedded MOS capacitors is higher than reference samples. It has been found that its oxide quality is related to charge carriers and/or defect states in the interface of MOS capacitors.

중성자 조사한 4H-SiC MOSFET의 열처리에 의한 전기적 특성 변화

이태섭,안재인,김소망,박성준,조슬기,주기남,조만순,구상모,Lee, Taeseop,An, Jae-In,Kim, So-Mang,Park, Sung-Joon,Cho, Seulki,Choo, Kee-Nam,Cho, Man-Soon,Koo, Sang-Mo 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.4

In this work, we have investigated the effect of a 30-min thermal anneal at $550^{\circ}C$ on the electrical characteristics of neutron-irradiated 4H-SiC MOSFETs. Thermal annealing can recover the on/off characteristics of neutron-irradiated 4H-SiC MOSFETs. After thermal annealing, the interface-trap density decreased and the effective mobility increased in terms of the on-characteristics. This finding could be due to the improvement of the interfacial state from thermal annealing and the reduction in Coulomb scattering due to the reduction in interface traps. Additionally, in terms of the off-characteristics, the thermal annealing resulted in the recovery of the breakdown voltage and leakage current. After the thermal annealing, the number of positive trapped charges at the MOSFET interface was decreased.

중공사막을 이용한 무동력 휴대용 정수기(Wellspring)의 적정기술로서 적용

김유미(Yu-Mi Kim),최승은(Seung-Eun Choi),박은혜(Eun-Hye Park),이태섭(Taeseop Lee),구정은(Joung-Eun Gu),이강원(Kangwon Lee),김정학(Jeong-Hak Kim) 적정기술학회 2015 적정기술학회지(Journal of Appropriate Technology) Vol.1 No.1

People in developing countries have been easily exposed to the risk of waterborne diseases such as cholera, heterogeneity and skin diseases from accessing inadequate potable water. The World Health Organization (WHO) has recently reported that the Point-of-Use (POU) water treatment is an effective solution to reduce waterborne diseases in many developing countries. POU systems based on membranes are significantly attractive. Furthermore, avoiding the use of electricity is obviously one of the main merits to appropriate technology for helping them from water related diseases caused by poor sanitation and insufficient hygiene. Recently, Wellspring, a potable water purifier based on membranes, was developed by the domestic technology. Wellspring is composed of an activated carbon, depth-filter and hollow fiber membrane and operated by gravity as a driving force without the use of electricity. For application as an appropriate water purification technology, the water quality, flux, and sustainability of Wellspring were evaluated to prove its performance compared to other potable purifiers. Results showed a 99.91 ± 0.04% removal efficiency of Kaolin on turbidity and the highest recovery rate after backwashing. In addition, the recorded flux variation after backwashing was the most stable compared to others in a long-term test. Moreover pathogenic bacteria tests showed that the water produced was microbiologically safe as E. coli, P. aeruginosa and Salmonella were not detected and suitable for the standards for drinking water quality. As such, Wellspring can supply safe drinking water, opening up possibilities for application in other countries. 개발도상국의 국민들은 식수로 부적합한 음용수로 인해 콜레라, 이질, 피부병 등의 수인성 질병에 쉽게 노출되고 있으 며, 세계보건기구는 최근 이러한 문제를 해결하기 위해서는 적정기술을 혼합한 POU(Point-of-Use) 수처리 시스템이 효과적인 방법이 될 수 있다고 보고하였다. 분리막을 기본으로 하는 POU 시스템은 최근 탁도와 미생물을 제어하기 위한 시스템으로 상당한 관심을 받고 있으며, 국내에서도 Wellspring이라는 휴대용 정수장치가 개발되어 개발도상국에 안전한 물을 공급하기 위한 적정기술로서 적용되고 있다. 이 장치는 전력을 사용하지 않는 중력식 여과방식으로 활성 탄, 적층형 필터, 중공사막으로 구성되어 있다. 본 연구를 통해 휴대용 정수장치인 Wellspring의 성능을 평가하기 위해 생산된 물의 수질과 생산수량, 생산 지속성과 같은 정수장치의 성능을 테스트 하였으며 타사의 유사제품과 비교하였 다. 이 경우에 Wellspring은 99.91±0.04%의 높은 탁도 제거율과 역세 후 타사제품에 비해 높은 성능 회복률을 보였다. 또한 장기간 테스트에서 타사제품보다 안정적인 성능 변화를 보였다. Wellspring의 여과수에서 수인성 병원균인 E. coli, P. aeruginosa, Salmonella의 제거율을 확인한 결과 전혀 검출되지 않았으며 이는 먹는물 수질 기준을 만족하는 수준 이였다. 이 연구를 통해 휴대용 정수장치인 Wellspring은 안전한 음용수를 공급할 수 있는 정수장치로 평가 되었으며 개도국에 휴대용 정수처리 장치로서 적용 될 수 있다.

국소마취에 의한 성형외과 수술에서 보조적으로 사용된 정맥 마취의 효과

이태섭,방사익,강훈 大韓成形外科學會 1998 Archives of Plastic Surgery Vol.25 No.1

When operations in the field of plastic surgery are performed under local anesthesia, the degree of pain suffering the patients becomes different depending on the kind, dosage effective duration of anesthetic agent and the technique of the operator. Patients suffer from pain physically and psychologically when skin infiltration is carried out. Recently, out-patient surgery has increased in number, so the necessity of more complete analgesia for the patient undergoing surgery is required. Patients were operated under the local infiltrative anesthesia, and the supplemental intravenous anesthesia to kill pain. Patients were randomly divided into four groups differing in combinations of intravenous anesthetic agents, such as ketamine, midazolam, fentanyl that have potent analgesic sedative and amnesic effects. By random allocation patients received ketamine and midazolam(Group Ⅰ), ketamine and fentanyl(Group Ⅱ), midazolam and fentanyl(Group Ⅲ), ketamine, fentanyl arts midazolam(Group Ⅳ). The purpose of this study is to focus on the results obtained in four groups for finding out a more safe and less complicated combination of intravenous anesthetic agents and for standardization of dosage. In conclusion the group I (ketamine and midazolam) showed better results than other groups for the following reasons; no significant change in vital signs, no hypoxia no complication such as nausea, headache unpleasant dream, and hallucination, potent analgesia effects, amnesia. We have found this combination to be a highly satisfactory anesthesia and analgesia technique for outpatient plastic surgery from the standpoints of the surgeon and the patient.