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사공 건,김한근,조현철,박상하 東亞大學校 大學院 1992 大學院論文集 Vol.17 No.-
A topic of this study is focused on the magnetic properties of Ni-Zn ferrite dependent on heat treat-ments(60, 80, 95℃) and frequency. Ni-Zn ferrite powders were synthesized by wet-direct method using FeCl₂·6H₂O, NiCl₂·6H₂O and ZnCl₂ as starting raw materials. As a summary, the initial permeability, loss factor and magnetic reluctance in the frequencies of 10 KHz∼10MHz for the specimens by prepared on the 60(℃) heat treatment and sintering condition at 1100(℃) for 3 hours were 7, 1∼5×10?? and 14.7(AT/wb), respectively. The highest highest figure of merit (??×Q) at the 400(KHz) was 1,050.
Comprehensive Study of Quasi-Ballistic Transport in High- <tex> $\kappa$</tex>/Metal Gate nMOSFETs
Hyun Chul Sagong,Chang Yong Kang,Chang-Woo Sohn,Kanghoon Jeon,Eui-Young Jeong,Do-Young Choi,Chang-Ki Baek,Jeong-Soo Lee,Lee, J. C.,Yoon-Ha Jeong IEEE 2011 IEEE electron device letters Vol.32 No.11
<P>We study quasi-ballistic transport in nanoscale high-κ/metal gate nMOSFETs based on radio-frequency (RF) <I>S</I>-parameter analysis. An RF <I>S</I>-parameter-based simple experimental methodology is used for direct extraction of device parameters (i.e., <I>L</I><SUB>eff</SUB>, <I>R</I><SUB>sd</SUB>, and <I>C</I><SUB>inv</SUB>) and the effective carrier velocity v<SUB>eff</SUB> from the targeted short-channel devices. Furthermore, an analytical top-of-the-barrier model, which self-consistently solves the Schrödinger-Poisson equations, is used to determine the ballistic carrier velocity <I>v</I><SUB>inj</SUB> at the top of the barrier near the source. Based on the results of the experimental extraction and analytical calculations, backscattering coefficient <I>r</I><SUB>sat</SUB> and ballistic ratio <I>BR</I><SUB>sat</SUB> are calculated to assess the degree of the transport ballisticity for nMOSFETs. It is found that conventional high-κ/metal gate nMOSFETs will approach a ballistic limit at an effective gate length <I>L</I><SUB>eff</SUB> of approximately 7 nm.</P>
Hyun Chul Sagong,Chang Yong Kang,Chang-Woo Sohn,Do-Young Choi,Eui-Young Jeong,Chang-Ki Baek,Jeong-Soo Lee,Yoon-Ha Jeong IEEE 2011 IEEE electron device letters Vol.32 No.12
<P>The hot-carrier (HC) effect in high-k/metal-gate nMOSFETs is characterized using radio-frequency (RF) small-signal parameter analysis. To explain a novel HC degradation of RF small-signal parameters, we propose a modified surface channel resistance model that can be applied to not only conventional SiO<SUB>2</SUB>/poly-Si-gate nMOSFETs but also high-k/metal-gate nMOSFETs.</P>
PZT-에폭시 3-3 형 복합압전체 초음파 트랜스듀서를 사용한 3 차원 수종 물체인식
조현철,사공건,허진 한국센서학회 2001 센서학회지 Vol.10 No.6
In this study, 3-D underwater object recognition using the self-made 3-3 type composite ultrasonic transducer and modified SOFM(Self Organizing Feature Map) neural network are investigated. Properties of the self-made 3-3 type composite specimens are satisfied considerably with requirements as an underwater ultrasonic transducer's materials. 3-D underwater all objects recognition rates obtained from both the training data and testing data in different objects, such as a rectangular block, regular triangular block, square block and cylinderical block, were 100% and 94.0%, respectively. All objects recognition rates are obtained by utilizing the self-made 3-3 type composite transducer and SOFM neural network. From the object recognition rates, it could be seen that an ultrasonic transducer fabricated with the self-made 3-3 type composite resonator will be able to have application for the underwater object recognition.
Chang-Woo Sohn,Hyun Chul Sagong,Eui-Young Jeong,Do-Young Choi,Min Sang Park,Jeong-Soo Lee,Chang Yong Kang,Jammy, R,Yoon-Ha Jeong IEEE 2011 IEEE electron device letters Vol.32 No.4
<P>In this letter, we analyze the nonsaturating upturns of capacitance under strong accumulation bias in MOS capacitors with high-k dielectrics. By comparing the electrical properties of dielectric samples with and without HfO<SUB>2</SUB> and by varying the ambient temperature, it is found that the conduction through the shallow trap levels in the HfO<SUB>2</SUB> bulk produces not only a steady-state current but also a dynamic current, which, in turn, causes the upturn in capacitance. The addition of RC shunts to the conventional small-signal model is proposed to consider the dynamic leakage effect. The model's effectiveness is verified by fitting the measured impedance spectrum and the measured capacitance. We suggest that measuring at a high frequency of hundreds of megahertz eliminates the dynamic interaction by shallow trap levels, allowing gate capacitance to be successfully reconstructed.</P>
Device Design Guidelines for Nanoscale FinFETs in RF/Analog Applications
Chang-Woo Sohn,Chang Yong Kang,Rock-Hyun Baek,Do-Young Choi,Hyun Chul Sagong,Eui-Young Jeong,Chang-Ki Baek,Jeong-Soo Lee,Lee, J. C.,Yoon-Ha Jeong IEEE 2012 IEEE electron device letters Vol.33 No.9
<P>This letter proposes simple guidelines to design nanoscale fin-based multigate field-effect transistors (FinFETs) for radio frequency (RF)/analog applications in terms of fin height and fin spacing. Geometry-dependent capacitive and resistive parasitics are evaluated using analytic models and are included in a small-signal circuit. It is found that reducing the fin-spacing-to-fin-height ratio of FinFETs, as long as it is compatible with the process integration, is desirable for improving RF performance. This is because the current-gain cutoff frequency and the maximum oscillation frequency are affected by decreasing parasitic capacitance more than by increasing series resistance.</P>
Analytic Model of S/D Series Resistance in Trigate FinFETs With Polygonal Epitaxy
Chang-Woo Sohn,Chang Yong Kang,Myung-Dong Ko,Do-Young Choi,Hyun Chul Sagong,Eui-Young Jeong,Chan-Hoon Park,Sang-Hyun Lee,Ye-Ram Kim,Chang-Ki Baek,Jeong-Soo Lee,Lee, J. C.,Yoon-Ha Jeong IEEE 2013 IEEE transactions on electron devices Vol.60 No.4
<P>In this paper, a simple but accurate model is presented to analyze source/drain (S/D) series resistance in trigate fin field-effect transistors, particularly on triangular or pentagonal rather than rectangular epitaxy. The model includes the contribution of spreading, sheet, and contact resistances. Although the spreading and sheet resistances are evaluated modifying standard models, the contact resistance is newly modeled using equivalent models of lossy transmission lines and transformations of 3-D to 2-D geometry. Compared with series resistance extracted from 3-D numerical simulations, the model shows excellent agreement, even when the S/D geometry, silicide contact resistivity, and S/D doping concentration are varied. We find that the series resistance is influenced more by contact surface area than by carrier path from the S/D extension to the silicide contact. To meet the series resistance targeted in the semiconductor roadmap, both materials and geometry will need to be optimized, i.e., lowering the silicide contact resistivity and keeping high doping concentration as well as maximizing the contact surface area, respectively.</P>