CBD 방법에 의한 CdS 박막의 성장과 광전도 특성

황광준,이상열,유상하,서상석,문종대,신영진,정태수,신현길,김택성,송정훈,유기수 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-

Chemical bath deposition 방법으로 다결정 CdS 박막을 세라믹 기판 위에 성장시킨 다음 온도를 변화시켜 열처리하고 X-선 회절무늬를 측정하여 결정구조를 밝혔다. 550℃로 열처리한 시료의 경우 X-선 회절무늬로 부터 외삽법에 의해 a_。와 c_。는 각각 4.1364 Å과 6.7129 Å인 육방정계임을 알았다. 이 때 낱알크기는 약 0.35㎛이었다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자 농도와 이동도의 온도의존성을 연구하였다. 이동도는 33 K 에서 150 K 까지는 압전산란에 의하여, 150 K 에서 293 K 까지는 극성광학산란에 의하여 감소하는 경향이 나타냈다. 광전도 셀의 특성으로 스텍트럼 응답, 감도(γ), 최대허용소비전력 및 응답 시간을 측정하였다. Polycrystalline CdS thin films were grown on creamic substrate using a chemical bath deposition method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdS polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdS samples annealed in N_2 gas at 550℃ it was found hexagonal structure whose lattice constants a_o and c_o were 4.1364 Å and 6.7120Å, respectively. Its grain size was about 0.35 ㎛. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33K and 150K and by polar optical scattering at temperature range of 150K and 293K. We measured also spectral response, sensitivity (γ), maximum allowable power dissipation and response time on these samples.

The partitioned-layer index: Answering monotone top-k queries using the convex skyline and partitioning-merging technique

Heo, J.S.,Whang, K.Y.,Kim, M.S.,Kim, Y.R.,Song, I.Y. North-Holland [etc ; Elsevier Science Ltd 2009 Information sciences Vol.179 No.19

A top-k query returns k tuples with the highest (or the lowest) scores from a relation. The score is computed by combining the values of one or more attributes. We focus on top-k queries having monotone linear score functions. Layer-based methods are well-known techniques for top-k query processing. These methods construct a database as a single list of layers. Here, the ith layer has the tuples that can be the top-i tuple. Thus, these methods answer top-k queries by reading at most k layers. Query performance, however, is poor when the number of tuples in each layer (simply, the layer size) is large. In this paper, we propose a new layer-ordering method, called the Partitioned-Layer Index (simply, the PL Index), that significantly improves query performance by reducing the layer size. The PL Index uses the notion of partitioning, which constructs a database as multiple sublayer lists instead of a single layer list subsequently reducing the layer size. The PL Index also uses the convex skyline, which is a subset of the skyline, to construct a sublayer to further reduce the layer size. The PL Index has the following desired properties. The query performance of the PL Index is quite insensitive to the weights of attributes (called the preference vector) of the score function and is approximately linear in the value of k. The PL Index is capable of tuning query performance for the most frequently used value of k by controlling the number of sublayer lists. Experimental results using synthetic and real data sets show that the query performance of the PL Index significantly outperforms existing methods except for small values of k (say, k=<9).

Chemical Bath Deposition 방법으로 제작한 CdSe 박막의 특성

홍광준,이상열,유상하,서상석,문종대,신영진,정태수,신현길,김택성,송정훈,유기수 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-

Chemical bath deposition 방법으로 다결정 CdSe 박막을 세라믹 기판 위에 성장시킨 다음 온도를 변화시켜 열처리하고 X-선 회절무늬를 측정하여 결정구조를 밝혔다. 450℃로 열처리한 시료가 X-선 회절무늬로 부터 외삽법에 의해 a_o와 c_o 는 각각 4.302 Å과 7.014 Å인 육방정계임을 알았다. 이 때 낱알크기는 약 0.3㎛이었다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자 농도와 이동도의 온도의존성을 연구하였다. 이동도는 33 K 에서 200 K 까지는 압전산란에 의하여, 200 k 에서 293 K 까지는 극성광학산란에 의하여 감소하는 경향이 나타냈다. 광전도 셀의 특성으로 스텍트럼 응답, 감도(γ), 최대허용소비전력 및 응답 시간을 측정하였다. Polycrystalline CdSe thin films were grown on creamic substrate using a chemical bath deposition (CBD) method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdSe polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdSe samples annealed in N_2 gas at 450℃ it was found hexagonal structure whose lattice parameters a_o and c_o were 4.302 Å and 7.014 Å, respectively. It grain size was about 0.3 ㎛. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33 K and 200 K, and by polar optical potical scattering at temperature range of 200 K and 293 K. We measured also spectral response, sensitivily (γ), maximum allowable power dissipation and response time on these samples.

Chemical Bath Deposition 방법으로 제작한 CdSe 박막의 특성

신영진 ( Y . J . Shin ),홍광준 ( K . J . Hong ),이상열 ( S . Y . Lee ),유상하 ( S . H . You ),서상석 ( S . S . Suh ),문종대 ( J . D . Moon ),신현길 ( H . K . Shin ),김택성 ( T . S . Kim ),송정훈 ( J . H . Song ),유기수 ( K . S . R 한국센서학회 1993 센서학회지 Vol.2 No.1

Polycrystalline CdSe thin films were grown on ceramic substrate using a chemical bath deposition (CBD) method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdSe polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdSe samples annealed in N₂ gas at 450℃ it was found hexagonal structure whose lattice parameters a_o and c_o were 4.302 A and 7.014 A, respectively. Its grain size was about 0.3 ㎛. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33 K and 200 K, and by polar optical scattering at temperature range of 200 K and 293 K. We measured also spectral response, sensitivity (γ), maximum allowable power dissipation and response time on these samples.

Current Status of the KSTAR TF Superconducting Magnet Development

ByoungSu Lim,C. S. Kim,D. J. Kim,D. K. Lee,G. S. Lee,H. K. Park,I. S. Woo,J. S. Bak,J. Y. Choi,J.J. Joo,K. Pak,K. Kim,K. P. Kim,M. S. Ko,N. H. Song,S. Lee,S. J. An,W. Chung,W. W. Park,Y. J. Song 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III

The KSTAR (Korea Superconducting Tokamak Advanced Research) TF magnet system is a fully superconducting magnet system which consists of 16 TF coils. The TF coil system provides a field of 3.5 T at a plasma center, with a peak flux density at the TF coils of 7.5 T. The stored energy is 470 MJ. TF coils use a Nb3Sn superconducting strand with Incoloy alloy 908 (afterward, Incoloy 908) conduit. The Nb3Sn strand has KSTAR HP-III specifications in which the critical current density is greater than 750 A/mm2 at 12 T, 4.2 K. The nominal current of the TF coils is 35.2 kA with all coils in series. For the fabrication of CICC (Cable-In-Conduit Conductor), a continuous CICC jacketing system is developed, and the procedures of coil fabrication are established to develop the TF coil. The prototype TF coil and the TF 01 16 coils are fabricated for the KSTAR superconducting magnet system. The TF17 coil which will be used as a back up coil is under fabrication. The overall TF coil fabrication will be completed by the end of December 2005.=

Features and Properties of $YBa_2$$Cu_3$$O_{7-x}$ Films Grown on SrTi$O_3$ by High Frequency PLD

Shi, D.Q.,Ko, R.K.,Song, K.J.,Chung, J.K.,Choi, S.J.,Park, Y.M.,Shin, K.C.,Yoo, S.I.,Park, C. The Korean Superconductivity Society 2003 Progress in superconductivity Vol.5 No.1

YBCO films were deposited with various thicknesses from 100nm to 1.6$\mu\textrm{m}$ on single crystal $SrTiO_3$ substrates by pulsed laser deposition (PLD). The effects of different deposition conditions, especially different deposition rates by means of changing the pulsed laser frequency up to 200Hz, on the J$_{c}$ value were studied. For YBCO film with the thickness of 200nm, the $J_{c}$ value of $2.1MA/\textrm{cm}^2$ has been achieved under the high deposition rate of 3.2nm/s (190nm/min). The $J_{c}$ can be maintained greater than $1M/\textrm{cm}^2$ with the thickness less than 1$\mu\textrm{m}$. The X-ray analysis was used to examine the texture, crystallization and surface quality. The SEM was employed to analyze the surface of YBCO, and it was shown the surface of YBCO film became rougher with increasing the thickness. There were many large singular outgrowths and networks of outgrowths on the surface of YBCO films which lowered the density of thick YBCO film. The outgrowth network was probably the a-axis YBCO corresponding to XRD $\theta$-2$\theta$scan and $\chi$-scan which were used to characterize a-axis orientation of YBCO film. The reason for J$_{c}$ declining with increasing the thickness was studied and discussed.sed.

Thermal and Electrical Stabilities of Solid Nitrogen (SN2) Cooled YBCO Coated Conductors for HTS Magnet Applications

Song, J B,Kim, K J,Kim, K L,Lee, J H,Kim, H M,Lee, G H,Chang, H M,Park, D K,Ko, T K,Lee, H G IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3

<P>Recently, a cooling system using a solid cryogen such as solid nitrogen (SN2), was introduced for high temperature superconducting (HTS) magnet applications. In order to apply the SN2 cooling system successfully to HTS applications, it is essential to obtain sufficient data regarding the characteristics of the SN2-cooled YBCO-coated conductor (CC), including the thermal and electrical properties. Therefore, this study examined the effect of SN2 on the thermal/electrical stability of YBCO CC tape. The SN2 was produced by conduction cooling using a GM-cryocooler and cooled to 58 K. The voltages and temperatures of the YBCO CC tapes were measured while applying an over-current. The results showed that the thermal and electrical stability of the YBCO CC tape were improved considerably in the SN2 cooling system compared to that in the conduction cooling system.</P>

Normal Zone Initiation and Propagation Characteristics of a Solid Nitrogen Cooled GdBCO Racetrack Pancake Coil

Song, J. B.,Kim, K. L.,Yang, D. G.,Jang, J. Y.,Ko, T. K.,Ahn, M. C.,Lee, H. G. IEEE 2012 IEEE transactions on applied superconductivity Vol.22 No.3

<P>This paper presents quench test results, of both experiment and simulation, of a racetrack pancake coil wound with a GdBCO-coated conductor tape in a solid nitrogen (SN2) cooling system at 58 K. The longitudinal normal zone propagation velocities in the curved section were 2 times faster than those in the straight section. Therefore, the straight section should be protected more than the curved section when using racetrack-type, GdBCO pancake coils in large-scale rotating machines. The simulated results showed good agreement with the experimentally observed normal zone initiation times.</P>

Ion beam induced atomic transport in bilayer systems

J.H.Son,T.G.Kim,G.S.Chang,C.N.Whang,J.H.Song,K.H.Chae 한국물리학회 2002 Current Applied Physics Vol.2 No.2

Atomic transport in ion beam mixed Co/Pt and Pd/Au bilayer systems have been studied from the shifts of maker layers inRutherford backscattering spectroscopy. Thin layers (1 nm) of marker (Pd for Co/Pt and Ni for Pd/Au) were embedded as markersat each interfaces. 80 keV Arþ was used to irradiate the marker samples at the temperature range between 90 and 600 K. The Co/PtJCo=JPt. 1:1) at low temperatures and anisotropic atomic transport (JCo=JPt. 5:0) athigh temperatures. Meanwhile, the Pd/Au system shows near isotropic atomic transport (JPd=JAu . 1:2) at all temperatures ex-and the vacancy migration energy. Atomic transport in thermal spike regime is closely related with the activation energy for normalimpurity diusion. In radiation enhanced diusion regime, the cohesive energy and/or the vacancy migration energy plays adominant role for the atomic transport.. 2001 Elsevier Science B.V. All rights reserved.

M?ssbauer Spectroscopy on the Magnetic Hyper ne Interaction of Nonstoichiometric Europium Iron Garnet

J.G.Kim,S.H.Song,K.H.Han 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.2

The microscopic physical properties of the nonstoichiometric garnet Eu$_{1-x}$Fe$_{1+x}$O$_{3}$($x$=0.2) have been studied by using X-ray diffraction at room temperature and M\"{o}ssbauer spectroscopy within the temperature range from liquid nitrogen temperature to 560 K. The X-ray diffraction patterns of the sample show coexistence of dominant garnet and a small portion of an unknown crystal phase. However, the M\"{o}ssbauer spectrum for the sample near the N\'{e}el temperature, which was 549$\pm$5 K, shows that, within experimental errors, there were no other crystal phases. The average area ratio of a- to d-sites for the sample was 0.76, which implies the possibility of some vacancies exsisting at the a- and/or the d-sites. The temperature dependence of the magnetic hyperfine fields was analyzed by using the spin-wave theory and the molecular-field model. From the analysis, the average strength of the interaction and the molecular-field coefficients were determined to be 37.484 K and ($-$60.0, 95.5, $-$29.8)(mole/cm$^{3}$), respectively. From the relations among molecular-field coefficients, the ion distribution at the a- and the d-sites was \{Eu$_{3}$\}[Fe$_{1.95}$](Fe$_{2.82}$)O$_{12}$.