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전자밀도함수이론을 이용한 세륨 산화물의 (111) 표면에서 일어나는 물 흡착 과정 분석
최혁,강은지,김현유,Choi, Hyuk,Kang, Eunji,Kim, Hyun You 한국재료학회 2020 한국재료학회지 Vol.30 No.5
Cerium oxide (ceria, CeO<sub>2</sub>) is one of the most wide-spread oxide supporting materials for the precious metal nanoparticle class of heterogeneous catalysts. Because ceria can store and release oxygen ions, it is an essential catalytic component for various oxidation reactions such as CO oxidation (2CO + O<sub>2</sub> 2CO<sub>2</sub>). Moreover, reduced ceria is known to be reactive for water activation, which is a critical step for activation of water-gas shift reaction (CO + H<sub>2</sub>O → H<sub>2</sub> + CO<sub>2</sub>). Here, we apply van der Waals-corrected density functional theory (DFT) calculations combined with U correction to study the mechanism of water chemisorption on CeO<sub>2</sub>(111) surfaces. A stoichiometric CeO<sub>2</sub>(111) and a defected CeO<sub>2</sub>(111) surface showed different water adsorption chemistry, suggesting that defected CeO<sub>2</sub> surfaces with oxygen vacancies are responsible for water binding and activation. An appropriate level of water-ceria chemisorption energy is deduced by vdW-corrected non-local correlation coupled with the optB86b exchange functional, whereas the conventional PBE functional describes weaker water-ceria interactions, which are insufficient to stabilize (chemisorb) water on the ceria surfaces.
Programmable Metallization Cell 응용을 위한 Ag-doped 칼코게나이드 박막의 전기적 저항 변화 특성
최혁,구상모,조원주,이영희,정홍배,Choi, Hyuk,Koo, Sang-Mo,Cho, Won-Ju,Lee, Young-Hie,Chung, Hong-Bay 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.12
We have demonstrated new functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of silver via photo-induced diffusion in thin chalcogenide films is considered. The influence of silver on the properties of the newly formed materials is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Silver saturated chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in programmable metallization cell (PMC) devices. In this paper, we investigated electrical and optical properties of Ag-doped chalcogenide thin film on changed thickness of Ag and chalcogenide thin films, which is concerned at Ag-doping effect of PMC cell. As a result, when thickness of Ag and chalcogenide thin film was 30 nm and 50 nm respectively, device have excellent characteristics.