• Electronics and Telecommunications Trends
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• v.7 no.3
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• pp.154-164
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• 1992

고온초전도체의 전자응용 예를 들면, 죠셉슨접합과 같은 diode-type 의 초전도소자 뿐만 아니라 반도체 트랜지스터와 같은 고온초전도 삼단자소자의 개발 및 실용화를 위해서 해결해야 할 당면문제는 많다. 그 중에서 특히, 실리콘 기판위에 고온초전도 단결정박막을 성장시키는 것과 양질의 유전체 buffer층을 제조하는 것등이 있다. 초전도체/반도체구조에서 초전도전자쌍은 근접효과에 의해 반도체속으로 확산되어 가며, 이러한 현상을 이용하여 초전도 트랜지스터와 초전도 전자파소자와 같은 신기능 초전도소자를 구현할 수 있다. 그리고 이들 소자의 동작원리는 반도체속에서의 초전도 파동함수(질서파라미터)의 제어에 기초를 두고 있다. 고온초전도 일렉트로닉스를 겨냥하며, 중요한 응용으로서 거론되고 있는 분야는 1) one-wafer computer의 꿈을 실현하기 위한 기반기술로 꼽고 있는 초전도배선연구, 2) 성능에서 반도체소자를 능가하는 초전도소자, 3) 21세기를 전망하면서 집적회로 연구자들의 타깃이 되고 있는 초전도집적회로 및 일렉트로닉스, 그리고 4) 광범위한 응용이 기대되는 초정밀 센서인 SQUID 소자 등이 있다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.188-194
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• 1998

The GaSe:$Er^{3+}$(5mol%) single crystals grown by the Bridgman technique displayed a direct energy gap at 1.79 eV and an indirect energy gap of 1.62 eV at 300 ${\circ}^$K. Also an optical absorption peak by impurity was found at 6505 $cm^{-1}$. The peak identified the origin of the electronic transitions to be between the energy levels of $Er^{3+}$ ions.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.44-49
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• 2003

To obtain the surface roughness with range from 10nm to 1nm we need the study of ultra-precision machine, cutting condition, and materials. In this paper, the optimal cutting conditions for getting mirror surface of aluminum alloy have been examined experimentally by using ultra-precision turning machine and sing1e crystal diamond tool. In generally, the cutting conditions such as feed rate and depth of cut have effect on the surface roughness in ultra-precision turning. The result of surface roughness was measured by the ZYGO New View 200. Therefore, The surface roughness and cutting conditions has been clarified. The smooth surface of aluminum alloy less than 1nm RMS, 1nm Rmax can be obtained by the ultra-precision cutting.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.416-421
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• 2003

To obtain the surface roughness with range from l0nm to In n need a ultra-Precision machine, cutting condition and the study of materials. And n have to also consider the chip and vibration of diamond tool during processing. In this paper, the cutting conditions for getting mirror surface of aluminum alloy have been examined experimentally by using ultra-precision turning and single crystal diamond tool. In generally, the cutting conditions have effect on the surface roughness in ultra-precision turning. The result of surface roughness was measured by the ZYGO New View 200.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.5
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• pp.7-10
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• 1984

Generally, free carrier densities of single crystal semiconductors are indifferent to methods of measurement. Free carrier densities of CdSe thin films, however, were measured invarious values with different methods In this paper, C-V method, Seebeck effect and a.c. Hall effect were used to measure carries densities of CdSe thin films. Carrier densities of CdSe thin films were in the range of 10 - 10 carriers/㎤. And causes of different results were discussed.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.239-241
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• 1996

The energy gap of GaSe:$Er^{3+}$(5mol%) single crystals grown by the Bridgman technique displaced a direct energy gap at 1.79 eV and an indirect energy gap at 1.62 eV at $300^{\circ}K$ with the addition of Erbium. Also, an impurity optical absorption peak was found to have occurred at $6505\;cm^{-1}$. The peak identified the origin of the electronic transitions between the energy levels of $Er^{3+}$ ions when the addition of dopant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.327-327
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• 2007

$LiTaO_3$ single crystal has been studied for surface acoustic wave(SAW) applications. There are two kinds of $LiTaO_3$ single crystals, stoichiometric $LiTaO_3$ (SLT) and congruent $LiTaO_3$ (CLT). These two crystals show quite different dielectrical properties, which might be related with defects in crystals. In this study, we observed the domain boundary of SLT and CLT with scanning nonlinear dielectric microscopy and discussed the stress distribution in $LiTaO_3$ single crystals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.135-139
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• 2014

The hydride vapor phase epitaxy (HVPE) grown GaN samples to precisely measure the surface characteristics was applied to a molten KOH/NaOH wet chemical etching. The etching rate by molten KOH/NaOH wet chemical etching method was slower than that by conventional etching methods, such as phosphoric and sulfuric acid etching, which may be due to the formation of insoluble coating layer. Therefore, the molten KOH/NaOH wet chemical etching is a better efficient method for the evaluation of etch pits density. The grown GaN single crystals were characterized by using X-ray diffraction (XRD) and X-ray rocking curve (XRC). The etching characteristics and surface morphologies were studied by scanning electron microscopy (SEM). From etching results, the optimum etching condition that the etch pits were well independently separated in space and clearly showed their shape, was $410^{\circ}C$ and 25 min. The etch pits density obtained by molten KOH/NaOH wet chemical etching under optimum etching condition was around $2.45{\times}10^6cm^{-2}$, which is commercially an available materials.

• Journal of the Mineralogical Society of Korea
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• v.6 no.2
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• pp.116-121
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• 1993

A single crystla of zeolite $Na_{78}Rb_{28}-X$ (approximate composition) was prepared by exposing $Na_{92}-X$ at $350^{\circ}C$ to 0.1 Torr of rubidium vapor, and its structure was determined by single-crystal x-ray diffraction methods in the cubic space group, Fd3, ${\alpha}=25.045(4){\AA}$. The structure was refined to the final error indices $R_1=0.082$ and $R_2=0.084$ with 353 for which I>$3{\sigma}(I)$. Only about 28 of the 92 $Na^+$ ions per unit cell were reduced and only about 14 of the 28 $Na^0$ atoms produced were retained within the zeolite. A $Na_5{^{4+}}$ cluster is present within each sodalite cavity. It is a centered tetrahedron (like $CH_4$) with bond $length=2.80(2){\AA}$ and angle tetrahedral by symmetry, and shows the full symmetry of its site. $T_d$, at the center of the sodalite cavity. Each of the four terminal atoms of the $Na_5{^{4+}}$ cluster bond to three framework oxygens at $2.36(2){\AA}$. At the centers of some double 6-rings are sodium atoms which bridge linearly between $Na_5{^{4+}}$ clusters to form agglomerations such as short zig-zag chains $Na_5{^{4+}}$ clusters. Delocalized electrons, located primarily on the sodiums at centers of the sodalite and (likely) double-six-ring cavities, contribute to the stability of the clusters.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.16-21
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• 2001

Optical properties of $Ag_2CdSnSe_4$ and $Ag_2CdSnSe_4:Co^{+2}$ quaternary semiconductor single crystals grown by the chemical transport reaction method were investigated. The analysis of the X - ray powder diffraction measurements showed that these crystals have a wurtzite structure with lattice constants a = 4.357 $\AA$, c = 7.380 $\AA$, for $Ag_2CdSnSe_4$ and a = 4.885 $\AA$, c = 7.374 $\AA$, for $Ag_2CdSnSe_4:CO^{2+}$. The direct band gap at 298K, obtained from the optical absorption measurement, is found to be 1.21 eV for $Ag_2CdSnSe_4$ and 1.02 eV for $Ag_2CdSnSe_4:CO^{2+}$. The shrinkage of the band gap due to Co-doping is observed and is about 190 meV, We observed four absorption bands of $Co^{2+}$ ions in two near infrared regions of optical absorption spectra of $Ag_2CdSnSe_4$:$Co^{+2}$. These absorption bands were assigned as due to electronic transitions between the split energy levels of $Co^{2+}$ ions in $T_d$ crystal field under spin-orbit interactions.