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.

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.

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.

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.

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.

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.

형질전환 제초제저항성 벼 밀양 204호의 농업적 특성

정응기,이기환,원용재,박향미,전남수,최준호,구연충,한창덕,은무영,김태산,남민희 Plant molecular biology and biotechnology research 2005 Plant molecular biology and biotechnology research Vol.2005 No.

This study was conducted to investigated the major characteristics of genetically modified rice of "Milyang 204" originated from Dongjinbyeo compared to a non-transgenic rice varieties Dongjinbyeo and Junambyeo. Basta resistant transgenic rice lines carrying bar gene produced by the Yeongnam Agricultural Research Institute were evaluated for their agronomic characters. The transgenic Japonica rice of "Milyang 204" showed inferior phenotypic traits compared to a non-transgenic rice variety Dongjinbyeo and Junambyeo. On the basis of UPOV (Union Internationale Pour la Protaection des Obtentions Vegetables) and NSMO(National Seed Management Office) the transgenic "Milyang 204" showed difference in some traits out of some agronomic traits, such as leaf color, angle of flag leaf, number of spikelets, culm length, white core and white belly compared to the nontransgenic varieties rice.

Si 기판 위에 CeO_2 유전체 박막 성장

한재원,김상훈,한영기,최무용 성균관대학교 기초과학연구소 1994 論文集 Vol.45 No.1

CeO_2 single target을 사용하여 on-axis rf magnetron 스퍼터링 방법으로 Si(100) 단결정기판 위에 CeO_2 유전체 박막을 성장시킬 때 기판온도, 산소 부분압력, rf input power, 두께 등의 성장변수들이 박막 성장에 미치는 영향을 조사하여 (ℓ00) 방향 in-situ 성장의 적정조건을 찾는 연구를 하였다. 각기 다른 조건에서 제조된 박막의 X-ray 회절 방법에 의한 구조 분석과 SEM(Scanning Electron Microscopy)에 의한 표면의 미세 구조 분석을 통하여 그 특성을 조사한 결과 기판 온도, 산소 부분압력, rf input power 세기, 박막의 두께가 박막 성장에 결정적인 영향을 미치는 중요 성장 변수임을 확인하였다. CeO_2 박막은 target과 기판사이 거리 50㎜, 총압력 30mTorr일 때 기판 온도 800℃, 산소 부분압력 3 mTon, power 90 W(이때 성장속도 0.83Å/s), 성장시간 2시간(이때 두께 500Å)일 때(ℓ00) 방향으로 잘 성장되는 것을 발견하였다. We have studied systematically the optimum condition for in-situ perparation of CeO_2 thin film on Si(100 substrate by single-target rf-magnetron sputtering method. We examined effects of the substrate temperature, oxygen partial pressure, rf input power, and thickness by studying X-ray diffraction patterns and photographs of scanning electron microscopy of the grown films. We found that all of these parameters influence decisively on the struture of the grown films. We also found that the CeO_2 thin film grows well at∼800℃ of the substrate temperature, 3 mTorr of the oxygen partial pressure, 90 W of the rf input power(corresponding to 0.83Å/s of the deposition rate), and 5000 Å of the thickness for the total sputtering gas of 30 mTorr and the sputtering target of 2 inch diameter used.

Induction of apoptosis by deinoxanthin in human cancer cells.

Choi, Yong-Ji,Hur, Jung-Mu,Lim, Sangyong,Jo, Minho,Kim, Dong Ho,Choi, Jong-Il Potamitis Press 2014 Anticancer research Vol.34 No.4

<P>Deinoxanthin is unique carotenoid isolated from the radioresistant bacterium Deinococcus radiodurans. In the present study, the induction of apoptosis of cancer cells by deinoxanthin was investigated.</P>

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.