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.

Preparation of YBa₂CU₃O7-y Superconducting Thin Films by on - axis Sputtering

한재원(Jae Won Han),박정래(Jung Rae Park),최무용(Mu-yong Choi) 한국진공학회(ASCT) 1995 Applied Science and Convergence Technology Vol.4 No.2

각기 다른 스퍼터링 기체 압력과 타켓-기판 사이 거리하에서 on-axis 스퍼터링 방법으로 MgO(100) 기판 위에 YBa₂CU₃O_(7-y) 초전도 박막을 제조하였다. 적정하게 높은 스퍼터링 기체 압력을 사용할 경우 on-axis 방법으로도 off-axis 방법으로 제조한 박막에 비해 전기적, 구조적으로 우수한 양질의 박막을 c축으로 성장시킬 수 있었다. 스퍼터링 기체 압력 증가에 의한 resputtering 감소 효과가 타켓과 기판 사이의 거리 증가에 의한 resputtering 감소 효과보다 성장되는 박막의 초전도성 향상에 더욱 효과적이였다. 박막의 성장 속도가 빠를 경우 MgO 위에 YBCO 박막이 c축보다는 α축으로 성장하려는 경향을 보였다. 스퍼터링 기체 압력과 타켓-기판 사이의 거리가 성장되는 박막에 미치는 영향에 대해 임계온도, 100 K와 300 K에서의 저항비, X선 회절분석 등을 통하여 고찰해 본다. YBa₂Cu₃O_(7-y) thin films have been prepared on MgO(100) substrates placed on-axis to the target by de magnetron sputtering in a variety of oxygen/argon gas pressures with different substrate-target distances. We found that films with the c-axis perpendicular to the substrate deposited in an optimally high gas pressure with on-axis substrate-target configuration exhibit such good electrical and structural properties as those deposited with off-axis configuration do. Increasing the substrate-target distance was found to be effective in reducing the resputtering effect and enhancing superconductivity of films, but not so much as increasing the gas pressure was. We also found that high deposition rates may promote mixed α- and c-axis growth of YBCO films on MgO substrates. Dependences of the T_c, the ratio of resistances at 300 K and 100 K, and the X-ray diffraction pattern on the gas pressure and the substrate-target distance are described.

고압 스퍼터링 방법으로 YBa₂Cu₃O7-y 박막을 제조할 때 기판의 접지 여부와 인가전류의 양이 박막 성장에 미치는 영향

한재원(Jae-Won Han),조광행(Kwang-Haeng Cho),최무용(Mu-Yong Choi) 한국진공학회(ASCT) 1995 Applied Science and Convergence Technology Vol.4 No.1

직경 2 인치의 YBa₂Cu₃O_(7-y) 타켓을 사용하여 높은 스퍼터링 기체 압력 하에서 off-axis DC-마그네트론 스퍼터링 방법으로 MgO(100) 단결정 기판 위에 YBa₂Cu₃O_(7-y) 박막을 c축 방향으로 in-situ 성장시킬 때 기판의 접지 여부와 인가전류의 양이 박막 성장에 미치는 영향을 연구하였다. 그 결과 접지 여부는 박막의 초전도 변환온도, 전기수송 특성, 결정 구조적 특성에는 영향을 거의 주지 않는 반면 표면상태에는 상당한 영향을 미치며, 인가전류의 양은 초전도 특성에 많은 영향을 미침을 발견하였다. 기판온도 670℃, 스퍼터링 기체압력 300 mTorr, 아르곤 대 산소 분압비 5 : 1의 조건에서 인가전류의 최적량은 300~500 mA이었으며 평균 박막 성장속도는 0.11~0.14Å/s로 매우 낮았다. 기판의 접지 효과와 낮은 성장속도의 원인에 대해 고찰해 본다. We have examined effects of substrate-grounding and the sputtering current on the superconducting and structural properties of the YBa₂Cu₃O_(7-y) thin-film grown on a MgO(100) single-crystal substrate by using the single-target off-axis DC-magnetron sputtering method. We found that grounding the substrate does not have any significant effect on the. superconducting transition temperature and the structure, but changes the surface morphology of the grown film. We also found that the amount of sputtering current is one of the important parameters to decide the superconducting property of the film. The optimum amount of the sputtering current is found to be 300~500 mA for 670℃ of the substrate temperature, 300 mTorr of the sputtering gas pressure, 5 : 1 of the partial-pressure ratio of Ar and O₂ gas, and 2-inch diameter of a sputtering-target used. The deposition rate for 300~500 mA was as low as 0.11~0.14Å/s. Origins of the substrate-grounding effects and the low deposition rate are discussed.

고압 스퍼터링 방법에 의한 YBa₂Cu₃O7-y 박막의 α축 방향 성장

송영조(Young-Jo Song),한재원(Jae-Won Han),최무용(Mu-yong Choi) 한국진공학회(ASCT) 1995 Applied Science and Convergence Technology Vol.4 No.2

YBa₂Cu₃O_(7-y) 박막을 c축 방향으로 성장시키는데는 고압 스퍼터링 방법이 저압 스퍼터링 방법에 비해 효과적인 것으로 알려져 있다. 우리는 500 mtorr의 고압 스퍼터링 방법을 사용하여 YBa₂Cu₃O_(7-y) 박막을 α축 방향으로 성장시키는 연구를 수행하였다. 저압 스퍼터링 방법을 사용할 때보다 낮은 기판온도에서 α축 방향 성장이 이루어지며, 저압 스퍼터링 성장의 경우와는 달리 산소분압의 크기에 따라 성장 방향이 달라지지 않음을 발견하였다. 성장된 박막은 기대와 달리 매우 낮은 초전도 전이온도와 열등한 구조적 특성과 표면 특성을 보였다. The high-pressure sputtering deposition is known to be so effective for preparing c-axis oriented YBa₂Cu₃O_(7-y) films. We have studied on growth of α-axis oriented films of YBa₂Cu₃O_(7-y) on SrTiO₃(100) substrates by sputtering under the high total pressure of 500 mtorr. It was found that the films grows α-axis oriented at lower substrate temperatures than for sputtering under low total pressures. The oxygen partial pressure which is known to influence the film growth orientation for low-pressure sputtering was not found to make any effect on the film orientation. The films exhibit lower transition temperatures and poorer structural coherence and surface morphology than expected.

전자선 리토그래피 방법을 이용한 나노 구조 제조

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.

Bi_2Sr_2Ca_(n-1)Cu_nO_y(n=1, 2, 3)의 열기전력 측정연구

김용민,최무용 성균관대학교 기초과학연구소 1989 論文集 Vol.40 No.2

We have measured the thermopower of three phases of Bi_2Sr_2Ca_(n-1)Cu_nO_y for n = 1, 2, 3. The thermopower is found to he larger when n is bigger and its temperature derivative dS/dT is negative irrespective of phases. For n=1, we find that the thermopower itself is negative for all the temperature range above 10K, and when the same sample has been baked in vacuum at 600℃, thermopower vs. temperature curve shows a broad positive peak similar to those seen in rare-earth high-Tc superconductors. Considering these experimental fact, the suggestion that the charge carriers in these materials are holes may be seriously challanged. We have considered a two-band model as an alternative where holes and electrons coexsist as charge carriers.

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.

자기장 속에서 2차원 조셉슨 접합 배열의 상전이

황성진,김지연,최무용 성균관대학교 기초과학연구소 1998 論文集 Vol.49 No.-

We have studied the phase transition of a Josephson-junction array in a magnetic field with the frustration index f = 1/5. The results of our experimental study were found to be quite different from those of the simulation work by Y. H. Li and S. Teitel which show two-step variations of the resistance with the temperature and the dc current and the first-order nature of a phase transition. The experiment revealed one-step variation of the resistance with the temperature above the critical temperature. Thermal hysteresis, an indication of a first-order phase transition, was not observed in the resistance measurements. The resistance was also found to increase in one step with the dc current and to exhibit no hysteresis when the current direction is reversed. Origin of the discrepancy between the results of the experiment and the simulation is discussed.

산소 결핍도 변화에 따른 YBa_2 Cu_3 O_7-y의 열기전력 변화

강원남,김용민,조경철,최무용 성균관대학교 기초과학연구소 1988 論文集 Vol.39 No.1

To clarify the superconducting mechanism of the high Tc oxide superconductors, we have studied the interactions among electrons and elementary excitations and the electronic energy band structure by measuring the thermoelectric power of YBa_2 Cu_3O_7-y with various oxygen deficiencies. We have found that the major charge carriers in YBa_2Cu_3O_7-y are holes, that the width of the electronic energy band is larger than the intial estimation, and that the interaction between electrons and phnonos in the material is not strong enough to explain the high Tc super conductivity, while we have seen an evidence that there exist strong interactions between electrons and magnetic excitations.