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정지남,엄지호,박병주,김선동,윤순길 한국물리학회 2017 Current Applied Physics Vol.17 No.5
For large-area Er0.4Bi1.6O3 (ESB) films on the Gd0.1Ce0.9O1.95 (GDC) pellets, the 300 nm-thick ESB films were deposited on the 0.2 cm-thick GDC pellets at different temperatures via on-axis sputtering and Facing-Target Sputtering (FTS) for enhancement of the ionic conductivity of the GDC. The ESB films deposited on the GDC pellets via FTS show a good step-coverage and a well-crystallization at a low temperature of 300 C. The ESB/GDC bilayers with lower activation energy than GDC single layer showed an enhanced ionic conductivity in intermediate-temperature range from 500 to 700 C. FTS is an attractive method for the ESB film deposition for low-temperature crystallization on the high-roughened GDC pellets.
박지현,엄지호,박병주,박기태,이수열,김경수,윤순길 한국물리학회 2015 Current Applied Physics Vol.15 No.11
Thin-film multi-layer ceramic capacitors (MLCCs) were prepared using high-dielectric constant Bi2Mg2/ 3Nb4/3O7 thin-films deposited at room temperature via radio-frequency magnetron sputtering. The multi-layer capacitors, in sizes 0402, 0603 and 1005, were well equipped with both inner and outer Cu electrodes. The capacitances of the bi-layer capacitors were twice that of the single-layer version in sizes 0402, 0603, and 1005. The 200 nm-thick Bi2Mg2/3Nb4/3O7 thin-films would be suitable for thin-film multi-layer capacitor applications.
실시간 XRD와 TEM을 이용한 MAPbI<sub>3</sub>의 온도 변화에 따른 구조 분석
최진석,엄지호,윤순길,Choi, Jin-Seok,Eom, Ji-Ho,Yoon, Soon-Gil 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.1
Methylammonium lead triiodide ($MAPbI_3$)-based perovskite solar cells potentially have potential advantages such as high efficiency and low-cost manufacturing procedures. However, $MAPbI_3$ is structurally unstable and has low phase-change temperatures ($30^{\circ}C$ and $130^{\circ}C$); it is necessary to solve these problems. We investigated the crystal structure and phase separation using real-time temperature-change X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy. $MAPbI_3$ has a tetragonal structure, and at about $35^{\circ}C$ the c-axis contracts, transforming $MAPbI_3$ into the related cubic crystal structure. In addition, at $130^{\circ}C$, phase separation occurs in which $CH_3NH_2$ and HI at the center of the unit cell of the perovskite structure are extracted by gas, leavingand only $PbI_2$ of the three-component structure, is produced as the final solid product.
실시간 XRD와 TEM을 이용한 MAPbI3의 온도 변화에 따른 구조 분석
최진석,엄지호,윤순길 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.1
Methylammonium lead triiodide (MAPbI3)-based perovskite solar cells potentially have potential advantagessuch as high efficiency and low-cost manufacturing procedures. However, MAPbI3 is structurally unstable and has lowphase-change temperatures (30℃ and 130℃); it is necessary to solve these problems. We investigated the crystalstructure and phase separation using real-time temperature-change X-ray diffraction, transmission electron microscopy,and electron energy loss spectroscopy. MAPbI3 has a tetragonal structure, and at about 35℃ the c-axis contracts,transforming MAPbI3 into the related cubic crystal structure. In addition, at 130℃, phase separation occurs in whichCH3NH2 and HI at the center of the unit cell of the perovskite structure are extracted by gas, leavingand only PbI2 ofthe three-component structure, is produced as the final solid product. 메틸암모늄납트요오드화물 (MAPbI3) 기반의 페로브스카이트 태양전지는 고효율 및 저비용 제조 설비와 같은 장점을 보인다. 그러나 MAPbI3는 구조적으로 불안정하고 낮은 상변화 온도 (30, 130℃)를 가지고 있기 때문에 이러한 문제를 해결할 필요가 있다. 우리는 실시간 온도 변화 X 선 회절, 투과 전자 현미경 및 전자 에너지 손실 분광법을 사용하여 온도 변화에 따른 결정 구조 및 상분리를 조사했다. MAPbI3는 정방 정계 구조를 가지며, C 축은 약 35℃에서 짧아진다. MAPbI3의 결정 구조는 정방 결정 구조에 가까운 입방체 계로 변형되었다. 또한, 130℃에서 페로브스카이트 구조의 C 축의 중심에 있는 CH3NH2와 HI가 가스에 의해 추출되고 3계 구조의 PbI2만이 고체로서 추출되는 상분리가 일어난다.
화학 기상 증착법을 이용한 유/무기 MAPbI<sub>3</sub> 페로브스카이트 박막 성장
정장수,엄지호,윤순길,Jung, Jang-Su,Eom, Jiho,Pammi, S.V.N.,Yoon, Soon-Gil 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.4
Methylammonium lead iodide (MAPbI<sub>3</sub>) thin films were grown at low temperatures on glass substrates via 3-zone chemical vapor deposition. Lead iodide (PbI<sub>2</sub>) and lead bis (dipivaloylmethanate) [Pb(dpm)<sub>2</sub>] precursors were used as lead sources. Due to the high sublimation temperature (~400℃) of the PbI<sub>2</sub> precursor, a low substrate temperature could not be constantly maintained. Therefore, MAPbI<sub>3</sub> thin films degraded into the PbI<sub>2</sub> phase. In contrast, for the Pb(dpm)<sub>2</sub> precursor, a substrate temperature of ~120℃ was maintained because the sublimation temperature of Pb(dpm)<sub>2</sub> is as low as 130℃ at a high vapor pressure. As a result, high-quality MAPbI<sub>3</sub> thin films were successfully grown on glass substrates using Pb(dpm)<sub>2</sub>. The rms (root-mean-square) roughness of MAPbI<sub>3</sub> thin films formed from Pb(dpm)<sub>2</sub> was as low as ~19.2 nm, while it was ~22.7 nm for those formed using PbI<sub>2</sub>. The grain size of the films formed from Pb(dpm)<sub>2</sub> was as large as approximately 350 nm.
화학 기상 증착법을 이용한 유/무기 MAPbI3 페로브스카이트 박막 성장
정장수,엄지호,S.V.N. Pammi,윤순길 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.4
Methylammonium lead iodide (MAPbI3) thin films were grown at low temperatures on glass substrates via 3-zone chemical vapor deposition. Lead iodide (PbI2) and lead bis (dipivaloylmethanate) [Pb(dpm)2] precursors were used as lead sources. Due to the high sublimation temperature (~400℃) of the PbI2 precursor, a low substrate temperature could not be constantly maintained. Therefore, MAPbI3 thin films degraded into the PbI2 phase. In contrast, for the Pb(dpm)2 precursor, a substrate temperature of ~120℃ was maintained because the sublimation temperature of Pb(dpm)2 is as low as 130℃ at a high vapor pressure. As a result, high-quality MAPbI3 thin films were successfully grown on glass substrates using Pb(dpm)2. The rms (root-mean-square) roughness of MAPbI3 thin films formed from Pb(dpm)2 was as low as ~19.2 nm, while it was ~22.7 nm for those formed using PbI2. The grain size of the films formed from Pb(dpm)2 was as large as approximately 350 nm. 본 연구에서는 3-Zone 화학 기상 증착법을 이용하여 유리 기판 상에 MAPbI3 박막을 저온에서 성장시켰다. MAPbI3 박막을 성장하기 위하여 PbI2 와 Pb(dpm)2 납 전구체로 사용하였다. PbI2 를 전구체로 사용한 경우, 기판 온도는 PbI2 의 높은 승화 온도 (약 400 ℃) 로 인해 저온에서 일정하게 유지되지 않아 MAPbI3 박막의 열적 열화로 인해 PbI2 로 분해 되었다. 반면, Pb(dpm)2 의 경우, 충분한 증기압을 얻기 위한 승화 온도가 약 130 ℃ 로 낮아서 120 ℃ 의 기판의 온도를 일정하게 유지할 수 있었다. 그 결과, Pb(dpm)2 를 이용하여 유리 기판 상에 고품질의 MAPbI3 박막을 성공적으로 성장시켰다. Pb(dpm)2 를 사용한 MAPbI3 박막의 rms 거칠기는 PbI2 를 사용한 것 (약 22.7 nm) 과 비교하여 약 19.2 nm 로 낮았으며, 결정립 크기는 평균 350 nm 로 성장하였다.
Ti (10 nm)-buffered 기판들 위에 저온에서 직접 성장된 무 전사, 대 면적, 고 품질 단층 그래핀 특성
한이레,박병주,엄지호,윤순길,Han, Yire,Park, Byeong-Ju,Eom, Ji-Ho,Yoon, Soon-Gil 한국재료학회 2020 한국재료학회지 Vol.30 No.3
Graphene has attracted the interest of many researchers due to various its advantages such as high mobility, high transparency, and strong mechanical strength. However, large-area graphene is grown at high temperatures of about 1,000 ℃ and must be transferred to various substrates for various applications. As a result, transferred graphene shows many defects such as wrinkles/ripples and cracks that happen during the transfer process. In this study, we address transfer-free, large-scale, and high-quality monolayer graphene. Monolayer graphene was grown at low temperatures on Ti (10nm)-buffered Si (001) and PET substrates via plasma-assisted thermal chemical vapor deposition (PATCVD). The graphene area is small at low mTorr range of operating pressure, while 4 × 4 ㎠ scale graphene is grown at high working pressures from 1.5 to 1.8 Torr. Four-inch wafer scale graphene growth is achieved at growth conditions of 1.8 Torr working pressure and 150 ℃ growth temperature. The monolayer graphene that is grown directly on the Ti-buffer layer reveals a transparency of 97.4 % at a wavelength of 550 nm, a carrier mobility of about 7,000 ㎠/V×s, and a sheet resistance of 98 W/□. Transfer-free, large-scale, high-quality monolayer graphene can be applied to flexible and stretchable electronic devices.
포토 리소그래피 공정을 위한 Ti(10 nm)-Buffered층 위에 직접 성장된 고품질 무전사 단층 그래핀 공정
오거룡,한이레,엄지호,윤순길,Oh, Keo-Ryong,Han, Yire,Eom, Ji-Ho,Yoon, Soon-Gil 한국전기전자재료학회 2021 전기전자재료학회논문지 Vol.34 No.1
Single-layer graphene is grown directly on Ti-buffered SiO2 at 100℃. As a result of the AFM measurement of the Ti buffer layer, the roughness of approximately 0.2 nm has been improved. Moreover, the Raman measurement of graphene grown on it shows that the D/G intensity ratio is extremely small, approximately 0.01, and there are no defects. In addition, the 2D/G intensity ratio had a value of approximately 2.1 for single-layer graphene. The sheet resistance is also 89 Ω/□, demonstrating excellent characteristics. The problem was solved by using graphene and a lift-off patterning method. Low-temperature direct-grown graphene does not deteriorate after the patterning process and can be used for device and micro-patterning research.