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Li<sub>2</sub>O Co-Sputtering을 통한 비정질 LLZO 고체전해질의 전기화학 특성 평가
박준섭,김종헌,김현석,Park, Jun-Seob,Kim, Jong-Heon,Kim, Hyun-Suk 한국재료학회 2021 한국재료학회지 Vol.31 No.11
As the size of market for electric vehicles and energy storage systems grows, the demand for lithium-ion batteries (LIBs) is increasing. Currently, commercial LIBs are fabricated with liquid electrolytes, which have some safety issues such as low chemical stability, which can cause ignition of fire. As a substitute for liquid electrolytes, solid electrolytes are now being extensively studied. However, solid electrolytes have disadvantages of low ionic conductivity and high resistance at interface between electrode and electrolyte. In this study, Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> (LLZO), one of the best ion conducting materials among oxide based solid electrolytes, is fabricated through RF-sputtering and various electrochemical properties are analyzed. Moreover, the electrochemical properties of LLZO are found to significantly improve with co-sputtered Li<sub>2</sub>O. An all-solid thin film battery is fabricated by introducing a thin film solid electrolyte and an Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> (LTO) cathode; resulting electrochemical properties are also analyzed. The LLZO/Li<sub>2</sub>O (60W) sample shows a very good performance in ionic conductivity of 7.3×10<sup>-8</sup> S/cm, with improvement in c-rate and stable cycle performance.
고분자 기판과 PECVD 절연막에 따른 ITZO 박막 트랜지스터의 특성 분석
양대규,김형도,김종헌,김현석,Yang, Dae-Gyu,Kim, Hyoung-Do,Kim, Jong-Heon,Kim, Hyun-Suk 한국재료학회 2018 한국재료학회지 Vol.28 No.4
We examined the characteristics of indium tin zinc oxide (ITZO) thin film transistors (TFTs) on polyimide (PI) substrates for next-generation flexible display application. In this study, the ITZO TFT was fabricated and analyzed with a SiOx/SiNx gate insulator deposited using plasma enhanced chemical vapor deposition (PECVD) below $350^{\circ}C$. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) results revealed that the oxygen vacancies and impurities such as H, OH and $H_2O$ increased at ITZO/gate insulator interface. Our study suggests that the hydrogen related impurities existing in the PI and gate insulator were diffused into the channel during the fabrication process. We demonstrate that these impurities and oxygen vacancies in the ITZO channel/gate insulator may cause degradation of the electrical characteristics and bias stability. Therefore, in order to realize high performance oxide TFTs for flexible displays, it is necessary to develop a buffer layer (e.g., $Al_2O_3$) that can sufficiently prevent the diffusion of impurities into the channel.
전자 사이클로트론 공명 플라즈마와 열 원자층 증착법으로 제조된 Al<sub>2</sub>O<sub>3</sub> 박막의 물리적·전기적 특성 비교
양대규,김양수,김종헌,김형도,김현석,Yang, Dae-Gyu,Kim, Yang-Soo,Kim, Jong-Heon,Kim, Hyoung-Do,Kim, Hyun-Suk 한국재료학회 2017 한국재료학회지 Vol.27 No.6
Aluminum-oxide($Al_2O_3$) thin films were deposited by electron cyclotron resonance plasma-enhanced atomic layer deposition at room temperature using trimethylaluminum(TMA) as the Al source and $O_2$ plasma as the oxidant. In order to compare our results with those obtained using the conventional thermal ALD method, $Al_2O_3$ films were also deposited with TMA and $H_2O$ as reactants at $280^{\circ}C$. The chemical composition and microstructure of the as-deposited $Al_2O_3$ films were characterized by X-ray diffraction(XRD), X-ray photo-electric spectroscopy(XPS), atomic force microscopy(AFM) and transmission electron microscopy(TEM). Optical properties of the $Al_2O_3$ films were characterized using UV-vis and ellipsometry measurements. Electrical properties were characterized by capacitance-frequency and current-voltage measurements. Using the ECR method, a growth rate of 0.18 nm/cycle was achieved, which is much higher than the growth rate of 0.14 nm/cycle obtained using thermal ALD. Excellent dielectric and insulating properties were demonstrated for both $Al_2O_3$ films.