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.

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.

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.

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.

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.

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.

Deposition of BZO nano-sized dots on the substrate surface for the enhanced magnetic properties of superconducting films

Chung, Kook-Chae,Yoo, Jai-Moo,Kim, Young-Kuk,Wang, X.L.,Dou, S.X. The Korean Society of Superconductivity and Cryoge 2008 한국초전도저온공학회논문지 Vol.10 No.2

Nano-sized dots have been formed on the buffered metal substrates using the novel approach of the electro-spray deposition, to modulate the substrate surface and induce the columnar defects in REBCO films grown on it. The $BaZrO_3$ precursor solution was synthesized and electro-sprayed out onto the negatively charged substrate surface. Using the electrostatic force, nano-sized dots can be grown and uniformly distributed on the buffered metal substrate. The height of BZO nanodots was observed above the 200nm, which are beneficial to induce the columnar defects onto the BZO as a seed. The density of BZO nanodots was also investigated and ${\sim}7.8/{\mu}m^2$ was obtained. As the deposition distance of electro-spray was shortened there was ${\sim}8times$ increase of density of nanodots. The optimization of process variables in electro-spray deposition are discussed in respect to the superconducting REBCO films processed by the Metal-Organic Deposition with the effective flux pinning properties.

Long Length YBCO Coated Conductors Prepared by an MOD Process on Buffered Metallic Tapes

Chung, Kook-Chae,Yoo, Jai-Moo,Ko, Jae-Woong,Kim, Young-Kuk,Kim, Tae-Hyung,Ko, Rock-Kil The Korean Society of Superconductivity and Cryoge 2006 한국초전도저온공학회논문지 Vol.8 No.4

YBCO coated conductors have been fabricated by the reel-to-reel processing using TFA-MOD method. In this work, the fluorine-free Y & Cu precursor solution was synthesized to shorten the calcining time by reducing the evolution of HF gas, thus the meter-long YBCO precursor films can be made within few hours by the continuous slot-die coating & calcination step using the F-free Y & Cu precursor solution. The annealing step was followed to make the YBCO films by the reel-to-reel method with the vertical gas flow system onto the moving tape. To increase the growth rate of the YBCO films by enhancing the removal of HF gas, the low total pressure was adopted in the annealing processing. And the water partial pressure and the oxygen partial pressure were varied to optimize the growth conditions of the MOD-YBCO films on the buffered metal tape. FE-SEM and XRD were used to investigate the surface morphologies and the texture of the meter-long YBCO films. The end-to-end critical current $(I_c)$ of 63A/cm-width and the critical current density $(J_c)$of $0.9MA/cm^2$ with the thickness of $0.7{\mu}m$ were obtained in the 0.42m long coated conductor.

초전도 자속고정 특성 향상을 위한 $ZrO_2$ 나노점의 형성 연구

Chung, Kook-Chae,Yoo, Jai-Moo,Kim, Young-Kuk,Lee, Hye-Moon,Wang, X.L.,Dou, S.X. 한국초전도저온학회 2008 한국초전도저온공학회논문지 Vol.10 No.1

To achieve high transport current without degradation under magnetic field, it is essential to artificially generate the pinning sites at which moving magnetic flux can be pinned. In this work, $ZrO_2$ nanodots were formed on the substrate surface using electro-spray deposition method. On top of the nanodots, the extended and effective pinning centers can be created. The positively charged Zr precursor solution was sprayed out from the needle using the corona discharge phenomena. Then, the sprayed precursor was deposited onto the negatively charged substrate surface followed by the heat treatment under the controlled atmosphere. Using the electrostatic force among the charged particles of precursor, evenly distributed and nano-sized dots were formed on the substrate surface. The size and density of the nanodots were studied by Atomic Force Microscopy. Also discussed are the effect of the deposition time and solution concentration on the size and density of the nanodot and processing variables in electro-spray method for the effective flux pinning centers in the superconducting films.