개선된 Bridgman법으로 성장한 Bi₂Sr₂CaCu₂O_(8+δ) 單結晶의 초전도성

채건식,손인호,설정식,이수대,김영국,전동성,오재근,강성욱 경남대학교 환경문제연구소 1995 환경연구 Vol.17 No.-

The Bi₂Sr₂CaCu₂O_(8)+_(δ) single crystals are grown from the melt using a stoichiometric starting composition fer the cautions. The size and thickness of the Bi₂Sr₂CaCu₂O_(8)+_(δ) crystals depends on the cooling rate. The lower the cooling rate, the bigger and thicker the Bi₂Sr₂CaCu₂O_(8)+_(δ) crystals become. Bi₂Sr₂CaCu₂O_(8)+_(δ) X-ray diffraction(XRD) measurements of the single crystals were carried out using the radiation source of Cu Kα . In these Patterns only the (0,0,2n) diffraction appeared. The result indicated that the cleared surface of the single crystal was of the a-b face, and that the single crystal had a single phase without any undergrowth with 7K and 85K phases. In addition, although the figure is not shown, XRD patterns from (006) to (00□) were observed in the range of 2θ=0 to 60 degrees. The characterization of as-grown single crystals have been analyzed by Laue X-ray backsdattering along the c-axis and X-ray precession experiments. The result of magnetic moment vs Tc in 10 Gauss for a crystals were measurements indicated that the samples have a superconducting transition temperature of 85K.

열확산법으로 만든 CdTe p-n 다이오드의 특성에 관한 연구

채건식,김영국,설정식,전동성 慶南大學校 附設 基礎科學硏究所 1990 硏究論文集 Vol.2 No.-

Single crystals of CdTe were grown by Bridgman method from a melt. They were contained the element of 0.1, 0.15, 0.2mole % In and 0.1mole % P as a dopant respectively. The crystallographic direction of the grown CdTe have zinc blende structure which is(331) plane 2θ=62.6。 in X-ray method. The etch pits on the (100), (110) and (111) surfaces grown to characteristics shapes with E-Ag or PBr was found to consider with the crystallographic direction denoted by simple Miller indices as is depicted schematically. Here the pits on (100), (110) and (111) show rectangular, triangular and conical shapes respectively. The results of PL measurements of undoped and In-doped CdTe showed the maximum peak at 7475 Å and 7503 Å, and P-doped CdTe by thermal diffusion showed the maximum peak at 6943 Å and 7478 Å , the former was shown by Al and the later by phosphorous. The values of the electrical chracteristics have been compared with the Yamada's and we showed the good agreements between them. The thickness if Al thermal diffusion to the CdTe crystals were propotional to the diffusion time. The properties of these cells have good rectification with forward and reverse voltage.

MgB₄O7 熱螢光體의 특성과 低에너지 X線의 線量測定

김영국,손인호,설정식,채건식,노경석 慶南大學校 附設 基礎科學硏究所 1997 硏究論文集 Vol.11 No.-

To develope the thermoluminescent radiation sensors and low energy X-ray of dosimetry. The TL phosphors of MgB₄O7 are prepared and their physical characteristics are investigated. MgB₄O7 : Tb. Tm. Dy. La. Ho. and Nd phosphors have been prepared by sintering around 580℃ for 2 hours followed by flowing Ar gas. Ar gas. Activation energy and kinetic order of main peak of glow curve were studied by two methods peak shape method and initial rise method. By these methods, the estimated activation energies were 0.76±0.02eV(Tb doped). 0.94±0.03(Tm doped). 0.72±0.02 (Dy doped). respectively. The activation energy frequency factor and kinetic order of thermoluminescent process for each TL phosphors are measured by analyzing the glow curve by initial rise. peak shape. different heating rate. isothermal decay method. And The emission spectra of TL phosphors are also measured. The TL phosphors prepared in this work may be utilized to radiation sensor elements becaue of their high sensitivity to low energy X-ray.

Lead Germanate 단결정의 초음파 감쇠

이수대,채건식,김영국,설정식 慶南大學校 附設 基礎科學硏究所 1989 硏究論文集 Vol.1 No.-

The temperature dependence of the ultrasonic velocity of 10 MHz and the absorption coefficient in the 10-30MHz range by the pulse echo method were determined in lead germanate single crystal. The velocity of longitudinal 10 MHz ultrasound along the c axis changed anomalously at the phase transition point and the jump was approximately 50m/sec. Near Curie point, the relaxation time and the kinetic coefficient of electric polarization from the Landau-Khalatnikov theory were calculated as ?? sec and ??, respectively. At room temperature, the viscosity tensor were measured as, ?? in the MKS units.

ZnSe의 광전압효과

박남천,채건식,김영국,설정식,손인호 慶南大學校 附設 基礎科學硏究所 1997 硏究論文集 Vol.10 No.-

We have measured the energy gap in ZnSe as a function of temperature by Laser-Generaeted Photocharge Voltage Spectroscopy(PVS). Trap levels were calculated quasi equibrium, peak shape, initial rise methods. And We have measured the Photocharge Voltage as a function of temperature with varing heating rate. The trapping cross-section of ZnSe was calculated by the methods of Grossweiner.

Al/p - Si MIS 형 태양전지의 물성에 관한 연구

이수대,채건식,설정식,김영국,김일홍 慶南大學校 附設 基礎科學硏究所 1989 硏究論文集 Vol.1 No.-

The metal-thin insulating film-semiconductor structure is currently receiving much attention in solar cell studies. In this a MIS solar cell consisting of aluminum on single and poly silicon with an interfacial oxide layer(∼20Å) have been fabricated by vacuum evaporation method and found a good reproducibility. Recent studies show the importance of surface and interfacial oxide thickness. An interfacial of 20∼30Å is optimum and may be achieved by furnace heating to 600℃ in 800cc/min O₂flow. These cells have good rectification with forward and reverse voltage under dark condition. The best Al/p-Si Si solar cell has an open circuit voltage Voc=0.4V, short circuit current density Isc=30mA/㎠, fill factor FF=0.58 and conversion efficiency η=10% for single crystal, and Voc=0.33 V, Isc=30mA/㎠, FF=0.49 and η=5% for poly crystalline silicon substrates for 70mA/㎠ irradiation of AM₂.

Hg₁-xMnxTe산화막의 홀효과에 관한 연구

오재근,최기영,송재흥,김영국,채건식,주유환,설정식,손인호,차성극,이상찬 慶南大學校 附設 基礎科學硏究所 1996 硏究論文集 Vol.8 No.-

HClO₄(pH:2) 수용액에서 양극산화 방법으로 HgMnTe(HMT)의 표면에 산화막을 형성 시켰다. 산화막의 두께는 SEM으로 측정하였으며 10㎛였다. 전류-전압 특성곡선을 얻어 산화 피크 전압으로부터 HTeO₂?, TeO?, HHgO₂? 막이 형성되었음을 알 수 있었다. 산화시키지 않은 HMT와 HClO₄수용액에서 산화시킨 HMT에 대해 Hall전압 및 자기저항을 각각 측정하였다. 홀전압과 자기저항은 HMT보다 HMT산화막에서 더 컸으며 이것은 HHgO₂? 공격자가 홀의 역할을 하고, TeO₄? 산화막은 전하의 포획도를 낮게하기 때문으로 생각할 수 있다. Anodic oxidation processes on HgMnTe surface has been studied in standard aqueous HClO₄(pH:2) solution. The 10㎛ thickness of the anodic oxide layers was measured by SEM. The Composition of the anodic oxide layers are evaluated from current-voltage(I-V) characteristic of HgMnTe Oxidation. The layers are composed of mixed oxide. ??, TeO₄, and?? in HClO₄solution. Transport properties have been investigated in HMT oxide layer made in HClO₄solution and virgin HMT samples at 300K. Hall voltage and magnetoresistance are greater in oxide layer HMT than virgin HMT. As a result, we know that the vacancy of ??in an anodic oxide layer acts as hole and the resulting oxide ?? layer exhibit a reduced degree of charge trapping and increase magnetoresistance.

Effect of water partial pressure on the texture and the morphology of MOD-YBCO films on buffered metal tapes

Chung, Kook-Chae,Yoo, Jai-Moo,Ko, Jae-Woong,Kim, Young-Kuk,Wang, X.L.,Dou, S.X. The Korean Society of Superconductivity and Cryoge 2007 한국초전도저온공학회논문지 Vol.9 No.2

The influence of water partial pressure in Metal-organic Deposition (MOD) method was investigated on the texture and the morphology of $YBa_2Cu_3O_{7-x}$ (YBCO) films grown on the buffered metal tapes. The water partial pressure was varied from 4.2% up to 10.0% with the other process variables, such as annealing temperature and oxygen partial pressure, kept constant. In this work, the fluorine-free Y & Cu precursor solution added with Sm was synthesized and coated by the continuous slot-die coating & calcination step. The next annealing step of the YBCO films was done by the reel-to-reel method with the gas flowed vertically down. From the x-ray diffraction analysis, the un-reacted phase like $BaF_2$ peak was found at the water partial pressure of 4.2%, but $BaF_2$ peak intensity is much reduced as the water partial pressure is increased. However, the higher water partial pressure of about 10% in this experiment leads to the poor crystallinity of YBCO films. The morphologies of the YBCO films were not different from each other when the water partial pressure was varied in this work. The maximum critical current density of 3.8MA/$cm^2$ was obtained at the water partial pressure of 6.2% with the annealing temperature of 780$^{\circ}C$ and oxygen partial pressure of 500ppm.

초전도 선재용 완충층의 결정성장 연구

Chung, Kook-Chae,Yoo, Jai-Moo,Kim, Young-Kuk,Wang, X.L.,Dou, S.X. 한국초전도저온학회 2007 한국초전도저온공학회논문지 Vol.9 No.3

All three buffer layers of $Y_2O_3$, YSZ, and $CeO_2$ have been deposited on the biaxially textured metal substrates using rf-sputtering method, The first 50-70nm thick $Y_2O_3$ films were grown epitaxially on biaxially textured metal substrates as a seed layer and followed by the diffusion barrier ${\sim}100nm$ thick YSZ and subsequent capping layer ${\sim}200nm$ thick $CeO_2$ deposited epitaxially on top of $Y_2O_3$ seed layer. The epitaxial orientation of all three layers were all (100) grown with rocking curve Full Width at Half Maximum(FWHM) of $4-5^{\circ}$ and in plane phi-scan FWHM of $6-8^{\circ}$ using X -ray diffraction analysis. The NiO phases formed during the $Y_2O_3$ seed layer deposition seem to degrade the crystallinity and roughen the surface morphology of the following layer observed by AFM(Atomic Force Microscopy). The buffered tapes were used as substrates for long length YBCO coated conductors with high critical current density $J_c$. The five multi-turn of metal tapes was employed to increase the thickness of films and production rate to compensate the low growth rate of rf-sputtering method.

일괄처리방식을 이용한 MOD 공정의 변수 최적화

Chung, Kook-Chae,Yoo, Jai-Moo,Ko, Jae-Woong,Kim, Young-Kuk,Wang, X.L.,Dou, S.X. 한국초전도저온학회 2006 한국초전도저온공학회논문지 Vol.8 No.1

Optimization of process variables, including oxygen and water partial pressure and also an nesting temperature, was performed in batch-type process to fabricate YBCO films on LaAlO3 single crystal. In this work, YBCO oxide powder was used as a starting precursor for metal-organic deposition(MOD)method. The precursor films were fabricated in batch furnace and they were converted to the epitaxial YBCO films at the same furnace with varying the process variables. The oxygen partial pressure was varied from 100ppm to 2000ppm and the water partial pressure from 1.2% to 12.2%. The window for optimal P(O2) was narrow about 700ppm for batch-type process. YBCO films in bathc-thype MOD process were optimized at 740-770oC and P(H2O) of 2.3%-7.3%.