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- 주제어 : Current atomic force microscopy (검색결과 5 건)
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Current Sensing Atomic Force Microscopy를 이용한 수화현상에 의한 Ionic Channel Network 변화 연구
권오성,이태동,이용욱,김주곤 한국물리학회 2015 새물리 Vol.65 No.4
Proton exchange membranes (PEMs) are being used as gas separators, insulating electrodes, and proton conductors. Thus, understanding the morphological structure of a PEM is one of the important issues for the characterization of a proton exchange membrane fuel cell (PEMFC). Specifically, the variation in the ionic channel network under hydration of a PEM is a crucial issue. In this study, we characterized the variation in the ionic channel network of Nafion 112 under a hydrated condition by using a current-sensing atomic force microscope (CSAFM). We built a mini-sized PEMFC by using the Pt-coated tip of a CSAFM and a PEM coated with Pt/C on one side. The mini-sized PEMFC could detect the local proton conductivity of the ionic clusters in the PEM. We measured the local proton conductivity of ionic clusters by using a mini-sized PEM under different relative humidities. The results were characterized by using the ballistic transport model and revealed several crucial trends, such as increasing proton conductivity and proton mean free path with increasing relative humidity. 이온교환막은 고분자 이온교환막 연료전지의 핵심부품으로써 음극과 양극으로 제공되는 수소와 산소를 분리하며, 음극과 양극을 전기적으로 절연시키며, 또한 연료전지가 양성자 전도도를 가지도록 하는 역할을 수행한다. 이러한 이유로 이온교환막의 구조를 이해하는 것은 연료전지를 분석하는데 있어서 중요한 주제 중의 하나이며 특히, 수화 현상에 의한 이온교환막 내부의 Ionic channel network의 변화를 분석하는 것은 가장 중요한 주제이다. 본 연구에서는 백금이 코팅된 current sensing atomic force microscope의 팁과 한쪽 면에만 전극이 부착 된 Nafion 112 맴브레인을 이용하여 미니 연료전지를 모사하였다. 미니 연료전지를 이용하여 ionic cluster들의 상대습도에 따른 미세한 양성자 전도도 측정하였으며 결과는 ballistic transport model을 이용하여 분석하였다. 그 결과 양성자 전도도는 및 양성자의 mean free path 또한 비선형적으로 증가함을 보였다.
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Microscopic conductivity of passive films on ferritic stainless steel for hydrogen fuel cells
Ahn Taemin,Kim Tae-Hwan 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.83 No.4
Hydrogen fuel cells ofer a clean and sustainable energy conversion solution. The bipolar separator plate, a critical component in fuel cells, plays a vital role in preventing reactant gas cross-contamination and facilitating efcient ion transport in a fuel cell. High chromium ferritic stainless steel with an artifcially formed thin chromium oxide passive flm has recently gained attention due to its superior electrical conductivity and corrosion resistance, making it a suitable material for separators. In this study, we investigate the microscopic electrical conductivity of the intrinsic passive oxide flm on such ferritic stainless steel. Through advanced surface characterization techniques such as current sensing atomic force microscopy and scanning tunneling microscopy/spectroscopy, we discover highly conductive regions within the flm that vary depending on location. These fndings provide valuable insights into the behavior of the passive oxide flm in fuel cells. By understanding the microscopic electrical properties, we can enhance the design and performance of separator materials in hydrogen fuel cells. Ultimately, this research contributes to a broader understanding of separator materials and supports the wider application of hydrogen fuel cells.
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Shi Jong Leem,Young Chul Shin,Eun Hong Kim,Chul Min Kim,이병규,이완호,Youngboo Moon,김태근 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.3
We report the effect of the barrier growth temperature of InGaN/GaN multi-quantum wells on the breakdown voltage of light emitting diodes. We adopted a two-step varied-barrier-growth temperature method to improve the structural and the electrical properties of the InGaN/GaN MQW layers. The depth of the V defect of InGaN/GaN MQW surfaces was decreased up to 20 °A by using a GaN barrier layer grown at a high growth temperature of 1000 C as compared to the conventional sample without varying the GaN barrier growth temperature. we found that the breakdown voltage increased to as high as about –25 V at a 10 μA reverse current.
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Woo, Hyunsuk,Vishwanath, Sujaya Kumar,Jeon, Sanghun Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.753 No.-
<P><B>Abstract</B></P> <P>Atomic switches are well-known promising candidates for future application in non-volatile logic memory devices. The resistive switching characteristics of these devices depend on the formation of a conductive filament (CF) by active metal electrodes. However, the formation of a stable CF is still a challenge owing to filament overgrowth in the solid electrolyte. To achieve controlled CF growth, we have used a modified active electrode with different Cu<SUB>x</SUB>Se<SUB>1−x</SUB> composition ratios (0.01 < x < 0.45) and a titanium (Ti) buffer layer. The optimum composition was determined to be Cu<SUB>0.11</SUB>Se<SUB>0.89</SUB>/Ti (2.5 nm) for which excellent resistive switching properties were observed, such as a high on/off ratio of 10<SUP>4</SUP>, low operating voltage, uniform resistance distribution, ten-year data retention at 85 °C, and <B>uniform endurance</B> (2000 cycles). The improvement is can be described from the high controllability of the oxidation-reduction reaction rate of the optimized CuSe modified active electrode by the means of Ti buffer layer and the TiO bond formation at the Ti/Al<SUB>2</SUB>O<SUB>3</SUB> interface. In addition, depth profiles of the conductive filament based on Cu<SUB>0.11</SUB>Se<SUB>0.89</SUB> with a Ti buffer layer were studied by performing current atomic force microscopy (I-AFM) to evaluate the enhancements in electrical performance and reliability resulting from the insertion of the Ti buffer layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First report on CuSe based atomic switch. </LI> <LI> Improved reliability depends on interface reaction at Ti/Al<SUB>2</SUB>O<SUB>3</SUB>. </LI> <LI> CuSe/Ti/Al<SUB>2</SUB>O<SUB>3</SUB>/Pt device showed highly stable retention at 102 °C for ten years. </LI> <LI> 860 nm<SUP>2</SUP> area of cross section of conductive filament is observed from I-AFM. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Resistive switching characteristics of CuSe/Ti-based atomic switch with controlled filament.</P> <P>[DISPLAY OMISSION]</P>
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