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최무용,송석표,정병직,김병호 한국전기전자재료학회 1999 전기전자재료학회논문지 Vol.12 No.1
Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$(x=0, 0.1, 0.2, 0.3) thin films were deposited on $Pt/SiO_2/Si$ substrate by MOD(Metalorganic Decomposition) process. Metal carboxylate and metal alkoxide were used as precursors, and 2-methoxyethanol, xylene as solvents. After spin coating, thin films were pre-annealed at $400^{\circ}C$, followed by RTA(Rapid Thermal Annealing) and final annealing at $800^{\circ}C$ in oxygen atmosphere. These procedures were repeated three times to obtain thin films with the thickness of $2000{\AA}$. To enhance the nucleation and growth of layered-perovskite phase, thin films were rapid-thermally annealed above $720^{\circ}C$ in oxygen atmosphere. As RTA temperature increased, fluorite phase was transformed to layered-perovskite phase. And the change of Nb contents affected dielectric / electrical properties and microstructure. The ferroelectric characteristics of $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ thin film were Pr=8.67 $\mu{C}/cm^2$, Ec=62.4kV/cm and $I_{L}=1.4\times10^{-7}A/cm^2$ at the applied voltage of 5V, respectively.
도시공간의 옛모습 추정을 위한 공간정보 플랫폼 구축 방안 연구
최무용(Choi, Mu-Yong) 대한건축학회 2018 대한건축학회논문집 Vol.34 No.9
It is a basic study to speculate the old form of urban space. The purpose of the study is to study how to build a database that can synthesize multiple data describing the past. In particular, It was focused to the first half time of Seoul City during the Chosun Dynasty. Data is structured systematically and inclusively through digitizing, visualization, and specification. Through this, the city`s urban space scene is reconstructed as a map of the city. And maps include various humanities information explaining the aspects of space activities. And it will become a system that will facilitate data management and improve the clarity of information.
Sound Velocity Measurements on (TMTSF)_2 CIO_4 in High Magnetic Fields
Choi, Mu-Yong 성균관대학교 기초과학연구소 1988 論文集 Vol.39 No.1
높은 자기장에서 (TMTSF)_2ClO_4의 소리속도와 감쇠계수를 측정하여 일정세기 이상의 자기장에서 소리속도와 감쇠계수가 계단모양으로 변화함을 보았다. 이같은 계단형태의 변화는 전자의 밀도와 폐르미 준위에서의 전자상태밀도의 계단형태의 감소를 의미하는 것으로서, 높은 자기장에서 전자계의 상태변환이 일어남을 시사한다.
Critical Field Anisotropy and Magnetoresistance Measurements on (BEDT-TTF)_2 Ⅰ_3
Choi, Mu-Yong 성균관대학교 기초과학연구소 1988 論文集 Vol.39 No.1
유기초전도체 β-(BEDT-TTF)_2I_3의 임계장 비등방성과 자기성 전기저항을 측정하였다. 임계장 비등방성은 a^*b^*평면에서는 작은 반면 a^*b^*평면에 수직한 면에서는 큼을 보았다. a^*와 b^*축 방향의 임계장의 온도곡선은 임계온도부근에서 위로 휘어진 반면, c^*축 방향의 임계장은 온도에 따라 선형의 변화를 보인다. 전기저항의 자기장에 따른 변화는 9K 이하에서 보통 금속의 경우와 다른 면모를 나타낸다. 이러한 실험 결과로부터 이물질의 초전도 현상은 조셉슨 연결에 의한 2차원 현상이며 9K까지 초전도 성질이 존재함을 알 수 있다.
Thermopower of RBa_2 Cu_3 O_(7-y) for R=Yb, Er, Dy, and Gd
Kang, Weon-Nam,Choi, Mu-Yong 성균관대학교 기초과학연구소 1989 論文集 Vol.40 No.1
We have measured the thermopower of RBa_2Cu_3O_(7-x), for R=Yb, Er, Dy, and Gd. We find that the thermopower is sensitive to the 3+ ion radius of the rare earth element in the material. For YbBa_2Cu_3O_(7-y), which has the rare earth element of the smallest ion-radius, the thermopower is negative unlike others. We also find that the thermopower vs. temperature curves are all similar in shape for every 1 : 2 : 3 compound, regardless of the sign of thermopower, charge carrier concentration and the rare earth element in the materials. As a plausible explanation for the experimental results, a two-band model is considered. Ever since the discovery of the new high-Tc superconductors, the electronic structure of the materials has been intensively studied. Despite a great deal of efforts, the electronic band structure, knowledge of which is essential to understand the superconducting mechanism in the materials, is not known in detail. In such a situation, the thermopower of the materials draws particular attention since it sensitively reflects the underlying electronic structural configuration. Measurements on selected high-Tc <원문페이지 누락>
김철균,최무용 성균관대학교 기초과학연구소 1998 論文集 Vol.49 No.-
In order to investigate the quantum-mechanical phenomena in mesoscopic systems, it is necessary to fabricate nano-scale structures. By using the electron-beam-direct-writing method and the lift-off method, we have successfully fabricated the quantum-dot gate structure with the gate width of 275 nm on a Si substrate. It is found that the optimal condition for writing the quantum-dot pattern on a 2,000Å-thick 4% - PMMA photo-resist is 90 seconds of develop time and 300 μC/㎠ of dose. It is also found that the optimal condition depends on geometry of nanostructure. It is necessary to find a new optimal condition for a pattern with a different geometry.
La_1.85Ba_0.15CuO_4-y에서 Cu 치환이 전기적 특성에 미치는 영향
서성완,최무용 성균관대학교 기초과학연구소 1994 論文集 Vol.45 No.1
산화물 고온초전도체 La_1.85Ba_0.15CuO_(4-y)에서 Cu를 전이금속 원소인 Co, Zn, Ni로 치환해 가면서 그에 따르는 열기전력과 비저항의 변화를 연구하였다. 이러한 전이금속 원소를 Cu 대신 치환했을 때 모든 경우 치환량이 증가할수록 임계온도는 급격히 감소한 반면 열기전력은 상대적으로 작은 변화를 보였다. 이것은 Zn, Co, Ni에 의한 임계온도 감소효과가 물질의 전자구조나 전도입자의 상태밀도 변화에 의한 것이 아님을 의미한다. 치환된 전이금속 원소들이 물질의 자기적 성질에 영향을 주는 가능성을 고려해 보았다. Thermopower and resistivity of La_1.85CuO_(4-y) with 3d transition metal atoms(Co, Zn, Ni) substituting for Cu were studied systematically as functions of the doping concentration. In all cases examined, T_ε decreases as the dopant concentration increases, but the thermopower shows little change in quantity. These experimental results indicate that the supression of superconductivity by transition metal atoms substitution in the material has not to do with change of the carrier concentration in the material. It is known that high-T_ε superconductivity has a close relation to antiferromagnetic ordering in CuO_2 plane. In this respect we take into consideration of the possibility that these 3d atoms may influence mangetic properties of the material.
Nd_(2-x)Ce_xCu_3O_(4-y)의 열기전력 측정연구
조경철,최무용 성균관대학교 기초과학연구소 1989 論文集 Vol.40 No.2
Measurments are made for the thermopower of N-type high-Tc oxide supercondutor Nd_(2-x)Ce_xCuO_(4-y), as functions of the amount of Ce dosage x, the oxygen deficiency y, and the temperature. When x or y is small, i.e. when the number of the doped electrons is small, the thermopower is found to be negative for the whole temperature range except for the lowest temperatures. For the samples wtih large x or y, on the other hand, we observed that the thermopower is positive against on expectation, for a broad temperature range from ∼20K up to room temperature. We have also found that there occurs a phase transition at around 200K, where the thermopower begins to change from negative to positive. These experimental results raise questions about the effects of the newly found phase transition on the electronic structure of the material, as well as about the general expectation that the charge carriers in this material may be electrons unlike other high-Tc supercondutor.