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HVPE 법을 활용한 GaN 성장 시 질화처리에 관한 연구
이승훈,이주형,이희애,오누리,이성철,강효상,이성국,양재득,박재화,Lee, Seung Hoon,Lee, Joo Hyung,Lee, Hee Ae,Oh, Nuri,Yi, Sung Chul,Kang, Hyo Sang,Lee, Seong Kuk,Yang, Jae Duk,Park, Jae Hwa 한국결정성장학회 2019 한국결정성장학회지 Vol.29 No.4
HVPE is one of the GaN single crystal manufacturing methods which has been commercially widely used due to its high growth rate. HVPE method consists of a number of processes, in particular the nitridation of the substrate prior to GaN growth has a significant effect on the crystalline quality of the manufactured GaN single crystal. In this study, we investigated the effect of nitridation for crystalline quality of GaN when it was grown on the sapphire substrate. The whole growth conditions except for the nitridation process were the same, and the gas flow rate supplied to the sapphire substrate was variously changed during the nitridation. Here, we examined the effect of nitridation via the surface characterization of GaN single crystal grown by HVPE. HVPE는 GaN 단결정의 제조 방법 중 하나로 빠른 성장 속도가 장점인 상업적으로 널리 사용되는 성장 방법이다. HVPE 법에 의한 GaN 단결정 성장은 여러 공정으로 이루어지며, 특히 GaN 성장 전 기판의 질화 처리는 성장되는 GaN 단결정 품질에 상당한 영향을 미친다. 본 연구에서는 사파이어 기판 위에 GaN 단결정 성장 시 기판의 질화처리가 성장되는 GaN 단결정 품질에 미치는 영향을 알아보고자 하였다. 질화 처리를 제외한 다른 성장 조건은 동일하게 하였고 질화처리 시 기판에 공급되는 가스 유량을 다양하게 변화시킨 후 GaN 박막을 성장시키고, 성장된 GaN의 표면 특성평가를 통하여, HVPE 법에서의 질화처리 효과를 고찰하여 보고자 하였다.
가소제 함유 PVDF 나노섬유의 상용화 가능성에 관한 연구
이승훈,소윤미,장선호,심현주,김찬,Lee, Seung-Hoon,So, Yun-Mi,Jang, Seon-Ho,Shim, Hyun-Joo,Kim, Chan 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.4
The mechanical properties and softness of electrospun polyvinylidene fluoride (PVDF) nanofibers was improved by the addition of a small amount of tributyl citrate (TBC) plasticizer to PVDF spinning solutions. The PVDF nanofibers containing TBC were prepared by electrospinning and subsequent calendering. The morphology, mechanical properties, and thermal properties of the electrospun PVDF nanofibers were investigated using Field Emission Scanning Electron Microscopy (FE-SEM), tensile test and DSC analysis. The results of the tensile experiment indicate that the PVDF nanofibers containing 5 wt% of TBC have three times better strength and six times higher elongation in the mechanical direction (MD) compared to those of pure PVDF nanofibers. Thus, the results indicate that PVDF nanofibers containing TBC have potential applications not only in the textile industry but also in the electrical and biomedical fields. Further, the excellent mechanical properties and softness of the eco-friendly nanofibers containing TBC plasticizer is useful for its commercialization.
CMOS 이미지 센서용 NMOS-Diode eFuse OTP 설계
이승훈,하판봉,김영희,Lee, Seung-Hoon,Ha, Pan-Bong,Kim, Young-Hee 한국정보통신학회 2016 한국정보통신학회논문지 Vol.20 No.2
본 논문에서는 프로그램 선택 소자는 채널 폭이 큰 NMOS (N-channel MOSFET) 트랜지스터 대신 DNW (Deep N-Well) 안에 형성된 채널 폭이 작은 isolated NMOS 트랜지스터의 body인 PW (P-Well)과 source 노드인 n+ diffusion 영역 사이에 형성된 기생하는 접합 다이오드를 사용하는 NMOS-Diode eFuse OTP (One-Time Programmable) 셀을 제안하였다. 제안된 eFuse OTP 셀은 프로그램 모드에서 NMOS 트랜지스터에 형성되는 기생하는 접합 다이오드를 이용하여 eFuse를 blowing 시킨다. 그리고 읽기 모드에서는 접합 다이오드를 이용하는 것이 아니고 NMOS 트랜지스터를 이용하기 때문에 다이오드의 contact voltage 강하를 제거할 수 있으므로 '0' 데이터에 대한 센싱불량을 제거할 수 있다. 또한 읽기 모드에서 채널 폭이 작은 NMOS 트랜지스터를 이용하여 BL에 전압을 전달하므로 OTP 셀의 blowing되지 않은 eFuse를, 통해 흐르는 읽기 전류를 $100{\mu}A$ 이내로 억제하여 blowing되지 않은 eFuse가 blowing되는 문제를 해결할 수 있다. In this paper, an NMOS-diode eFuse OTP (One-Time Programmable) memory cell is proposed using a parasitic junction diode formed between a PW (P-Well), a body of an isolated NMOS (N-channel MOSFET) transistor with the small channel width, and an n+ diffusion, a source node, in a DNW (Deep N-Well) instead of an NMOS transistor with the big channel width as a program select device. Blowing of the proposed cell is done through the parasitic junction formed in the NMOS transistor in the program mode. Sensing failures of '0' data are removed because of removed contact voltage drop of a diode since a NMOS transistor is used instead of the junction diode in the read mode. In addition, a problem of being blown for a non-blown eFuse from a read current through the corresponding eFuse OTP cell is solved by limiting the read current to less than $100{\mu}A$ since a voltage is transferred to BL by using an NMOS transistor with the small channel width in the read mode.
고선택비 인산공정에서의 식각율 향상과 SiO<sub>2</sub> 재성장에 관한 연구
이승훈,모성원,이양호,배정현,Lee, Seunghoon,Mo, Sungwon,Lee, Yangho,Bae, JeongHyun 한국재료학회 2018 한국재료학회지 Vol.28 No.12
To improve the etch rate of $Si_3N_4$ thin film, $H_2SiF_6$ is added to increase etching rate by more than two times. $SiO_3H_2$ is gradually added to obtain a selectivity of 170: 1 at 600 ppm. Moreover, when $SiO_3H_2$ is added, the etching rate of the $SiO_2$ thin film increases in proportion to the radius of the wafer. In $Si_3N_4$ thin film, there is no difference in the etching rate according to the position. However, in the $SiO_2$ thin film, the etching rate increases in proportion to the radius. At the center of the wafer, the re-growth phenomenon is confirmed at a specific concentration or above. The difference in etch rates of $SiO_2$ thin films and the reason for regrowth at these positions are interpreted as the result of the flow rate of the chemical solution replaced with fresh solution.
이승훈,최지호,Lee, Seung-Hoon,Choi, Ji-Ho 대한수면의학회 2005 수면·정신생리 Vol.12 No.2
Approximately 1% to 3% of all children have obstructive sleep apnea syndrome (OSAS). OSAS in children can lead to a variety of symptoms and sequalae; impairment of development and quality of life, behavioral and personality disturbance, learning problem, cor pulmonale and hypertension. Diagnosis and treatment of OASA for children are different from those for adults in many respects. Adenotonsillar hypertrophy is major cause of childhood OSAS. Overnight polysomnography in a sleep laboratory is the gold standard for diagnosing childhood OSAS. However, because full polysomnography in children may be difficult to obtain, expensive, and inconvenient, other methods to diagnose OSAS have been investigated. Adenotonsillectomy is the most common surgical treatment of childhood OSAS. But if residual symptoms remained after adenotonsillectomy, it should be considered to additional treatment such as weight control, sleep positional change, and continuous positive airway pressure (CPAP).
이승훈,윤종설,차영철,이준,황해진,문지웅,Lee, Seung-Hun,Yoon, Song-Seol,Cha, Young-Chul,Lee, Jun,Hwang, Hae-Jin,Moon, Ji-Woong 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.12
The potential candidates for IT-SOFCs cathode materials, $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ (BSCF) and $La_{0.6}Ba_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LBCF) powders, were synthesized by a EDTA-citrate combined method from $Sr(NO_3)_2$, $Ba(NO_3)_2$, $La(NO_3)_3{\cdot}6H_2O$, $Co(NO_3)_2{\cdot}6H_2O$, $Fe(NO_3)_3{\cdot}9H_2O$, citric acid and $EDTA-NH_3$. The cathode performance of symmetrical electrochemical cells consisting of BSCF-GDC or LBCF-GDC composite electrodes and a GDC electrolyte was investigated using by AC impedance spectroscopy at the temperature range of 500 to $700^{\circ}C$. It was found that a single phase perovskite could be successfully synthesized when the precursor is heated at $850^{\circ}C$ for 2 h. Due to thermal expansion mismatch between BSCF and GDC, the composite cathodes with lower GDC content than 45 wt% were peeled off from the GDC electrolyte and their electrode polarization resistance was estimated to be high. The thermal expansion coefficient of BSCF-GDC composites was decreased with increasing the GDC content and the electrode peeling off did not occur in BSCF-45 and 55 wt% GDC composites. BSCF-45 wt% GDC composite electrode showed the lowest area specific resistances (ASR) of 0.15 and $0.04{\Omega}{\cdot}cm^2$ at 600 and $700^{\circ}C$, respectively. On the other hand, LBCF-GDC composite cathodes showed higher ASR than the BSCF-45 and 55 wt% GDC and their cathode performance were decreased with the GDC content.
실리콘 이종접합 태양전지 특성에 대한 Zn 도핑된 ITO 박막의 일함수 효과
이승훈,탁성주,최수영,김찬석,김원목,김동환,Lee, Seung-Hun,Tark, Sung-Ju,Choi, Su-Young,Kim, Chan-Seok,Kim, Won-Mok,Kim, Dong-Hhwan 한국재료학회 2011 한국재료학회지 Vol.21 No.9
Transparent conducting oxides (TCOs) used in the antireflection layer and current spreading layer of heterojunction solar cells should have excellent optical and electrical properties. Furthermore, TCOs need a high work function over 5.2 eV to prevent the effect of emitter band-bending caused by the difference in work function between emitter and TCOs. Sn-doped $In_2O_3$ (ITO) film is a highly promising material as a TCO due to its excellent optical and electrical properties. However, ITO films have a low work function of about 4.8 eV. This low work function of ITO films leads to deterioration of the conversion efficiency of solar cells. In this work, ITO films with various Zn contents of 0, 6.9, 12.7, 28.8, and 36.6 at.% were fabricated by a co-sputtering method using ITO and AZO targets at room temperature. The optical and electrical properties of Zn-doped ITO thin films were analyzed. Then, silicon heterojunction solar cells with these films were fabricated. The 12.7 at% Zn-doped ITO films show the highest hall mobility of 35.71 $cm^2$/Vsec. With increasing Zn content over 12.7, the hall mobility decreases. Although a small addition of Zn content increased the work function, further addition of Zn content over 12.7 at.% led to decreasing electrical properties because of the decrease in the carrier concentration and hall mobility. Silicon heterojunction solar cells with 12.7 at% Zn-doped ITO thin films showed the highest conversion efficiency of 15.8%.
이승훈,이선영,김양수,양명식,차석용,Lee, seung hoon,Lee, sun young,Gim, yang soo,Kwak, Keun tak,Yang, myung sik,Cha, seok yong 대한방사선치료학회 2015 대한방사선치료학회지 Vol.27 No.2
목 적 : 고주파 온열치료 시 약물투여 및 혈액채취에 사용되는 케모포트로 인한 열적 변화를 알아보고자 한다. 대상 및 방법 : 전극 크기 20 cm인 고주파 온열치료기(EHY-2000, Oncotherm Kft, Hungary)를 이용하여 현재 본원에서 사용 중인 케모포트 중 재질이 플라스틱인 소재, 티타늄을 둘러싼 에폭시 소재와 티타늄 소재 케모포트를 자체 제작한 직경 20 cm, 높이 20 cm 원통형 한천(Agar)팬텀에 삽입하여 온도를 측정하였다. 온도측정기(TM-100, Oncotherm Kft, Hungary) 그리고 Sim4Life(Ver2.0, ZMT, Zurich, Switzerland) 프로그램을 사용하여 실제 측정된 온도변화와 비교 분석하였다. 측정위치는 전극 중심축 및 중심축 측면 1.5 cm지점에 각각 0 cm(표면), 0.5 cm, 1.8 cm, 2.8 cm 깊이별로 하였다. 측정조건은 온도 $24.5{\sim}25.5^{\circ}C$, 습도 30 ~ 32%, 출력 전력 100 W로 5분 간격으로 총 60분을 측정 하였다. 결 과 : 케모포트 미사용, 플라스틱, 에폭시 그리고 티타늄 케모포트를 사용한 경우의 최고온도는 전극 중심축 2.8 cm 깊이에서 측정값 $39.51^{\circ}C$, $39.11^{\circ}C$, $38.81^{\circ}C$, $40.64^{\circ}C$와 모의실험값 $42.20^{\circ}C$, $41.50^{\circ}C$, $40.70^{\circ}C$, $42.50^{\circ}C$이며, 전극 중심축 1.5 cm 측면 2.8 cm 깊이에서 측정값 $39.51^{\circ}C$, $39.32^{\circ}C$, $39.20^{\circ}C$, $39.46^{\circ}C$와 모의실험값 $42.00^{\circ}C$, $41.80^{\circ}C$, $41.20^{\circ}C$, $42.30^{\circ}C$이다. 고안 및 결론 : 고주파 전자기장에 의한 케모포트 주위의 열적 변화량은 부도체 물질인 플라스틱과 에폭시 소재에서 미사용의 경우보다 낮게 나타났으며, 도체 물질인 티타늄 케모포트에서는 약간의 차이를 보였다. 이는 케모포트내 금속 함유량 및 기하학적 구조에 의한 것과 이용 장비의 낮은 고주파 대역를 사용함에 있는 것으로 여겨진다. 즉 본 연구에 사용된 케모포트는 열 변화가 미미하여 장해를 고려하지 않아도 된다고 사료된다. Purpose : This study evaluate the thermal changes caused by use of the chemoport for drug administration and blood sampling during radiofrequency hyperthermia. Materials and Methods : 20cm size of the electrode radio frequency hyperthermia (EHY-2000, Oncotherm KFT, Hungary) was used. The materials of the chemoport in our hospital from currently being used therapy are plastics, metal-containing epoxy and titanium that were made of the diameter 20 cm, height 20 cm insertion of the self-made cylindrical Agar phantom to measure the temperature. Thermoscope(TM-100, Oncotherm Kft, Hungary) and Sim4Life (Ver2.0, Zurich, Switzerland) was compared to the actual measured temperature. Each of the electrode measurement position is the central axis and the central axis side 1.5 cm, 0 cm(surface), 0.5 cm, 1.8 cm, 2.8 cm in depth was respectively measured. The measured temperature is $24.5{\sim}25.5^{\circ}C$, humidity is 30% ~ 32%. In five-minute intervals to measure the output power of 100W, 60 min. Results : In the electrode central axis 2.8 cm depth, the maximum temperature of the case with the unused of the chemoport, plastic, epoxy and titanium were respectively $39.51^{\circ}C$, $39.11^{\circ}C$, $38.81^{\circ}C$, $40.64^{\circ}C$, simulated experimental data were $42.20^{\circ}C$, $41.50^{\circ}C$, $40.70^{\circ}C$, $42.50^{\circ}C$. And in the central axis electrode side 1.5 cm depth 2.8 cm, mesured data were $39.37^{\circ}C$, $39.32^{\circ}C$, $39.20^{\circ}C$, $39.46^{\circ}C$, the simulated experimental data were $42.00^{\circ}C$, $41.80^{\circ}C$, $41.20^{\circ}C$, $42.30^{\circ}C$. Conclusion : The thermal variations were caused by radiofrequency electromagnetic field surrounding the chemoport showed lower than in the case of unused in non-conductive plastic material and epoxy material, the titanum chemoport that made of conductor materials showed a slight differences. This is due to the metal contents in the chemoport and the geometry of the chemoport. And because it uses a low radio frequency bandwidth of the used equipment. That is, although use of the chemoport in this study do not significantly affect the surrounding tissue. That is, because the thermal change is insignificant, it is suggested that the hazard of the chemoport used in this study doesn't need to be considered.
해남 무논점파 논 KoFlux (HPK) 관측지: 소개
이승훈,강민석,강남구,김준,Lee, Seung-Hoon,Kang, Minseok,Kang, Namgoo,Kim, Joon 한국농림기상학회 2018 한국농림기상학회지 Vol.20 No.1
기후스마트농업의 관점에서 무논점파 농법의 경쟁력을 평가하기 위하여 플럭스 타워(HPK)를 설치, 에디 공분산 방법으로 이산화탄소, 메탄 그리고 에너지의 교환량을 지속적으로 관측하고 있다. 본 통신문에서는 HPK 관측지에 대한 소개와 관측 자료의 처리과정 및 품질 관리에 대하여 문서화 하였다. KoFlux 표준화 방법에 따른 10단계 자료 처리 및 품질 관리과정을 거쳤으며, 이 과정에서 HPK 관측지의 자료 사용자들이 알아야 할 중요한 보정 단계를 이해하기 쉽도록 각 방법에 대한 개념과 일반적인 예를 들어 설명하였다. 자료 처리 과정에서 생성된 모든 자료들을 정리하여 데이터 서버에 저장하였으며, 모든 처리 과정을 거친 최종 자료를 사용하여 HPK 관측지에서 2016년 생장기간 동안 관측된 주 요소들에 대해 간략히 정량화 하였다. A new eddy covariance-based flux tower has been established since June 2016 in a dry direct-seeding rice paddy field in southwestern Korea - Haenam Paddy field KoFlux site (HPK). To assess the competitiveness of direct-seeding agricultural technique in the context of climate-smart agriculture, we have been monitoring the $CO_2$, $CH_4$ and energy fluxes continuously. In this communication, we (1) introduce the HPK site and (2) explain the structure and processes of the HPK-specific data processing and quality control. The latter consists of 10-steps data processing and quality control procedures following the KoFlux standardized protocol and explained each step in layman's term. The final data produced during the data processing were stored in NCAM-DAPS (National Center for AgroMeteorology-Data Acquisition and Processing System, http://daps.ncam.kr). We hope that the introduction of new HPK KoFlux site would serve as a platform to facilitate transdisciplinary efforts in the research and education associated with climate-smart agriculture toward sustainability.