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Band Gap and Residual Entropy in the Spin Ice Material Dy2Ti2O7
Je Huan Koo,Kwang-Sei Lee 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.9
We investigate the origin of the band gap in the spin ice material Dy2Ti2O7. The band gap is caused by Bardeen-Cooper-Schrieffer (BCS)-type electron-electron interactions that are transformed from electron-ion interactions. Additionally, the residual finite entropy at absolute zero temperature results from band gap effects rather than the nature of the Pauling-type spin ice.
Quantized polariton in ferroelectric Rochelle salt
Kim, Yun Ki,Koo, Je Huan,Lee, Kwang-Sei Taylor Francis 2016 Ferroelectrics Vol.493 No.1
<P>In the presence of electric and gauge fields, it is possible to have effective charges, where an electron attached to an electric field flux can be termed a composite charge. Using the similar configuration of hydrogen, we calculate quantized energy eigenvalues for lattice ions, where the effective charge of an electron can assume a value of 0e or -2e and may be regarded as a photon composite; furthermore, polaritons from these composites can be quantized. We also compare our energy levels with experimental data obtained from inelastic neutron scatterings, in which the data above approximate to 3 meV ( = 24.1966 cm(-1)) may be attributed to phonon modes in ferroelectric Rochelle salt.</P>
Finite pseudo block spin model of ferroelectrics
Kim, Yun Ki,Koo, Je Huan,Lee, Kwang-Sei Taylor Francis 2016 Ferroelectrics Vol.494 No.1
<P>We herein explain the phase of ferroelectrics by reference to finite block spin theory, in which the phase of ferroelectrics may be considered as being a ferroelectric ordering between pseudo block spins comprised of random pseudo spins, that is, dipoles that have a majority of individual spins in a given sense. By making use of the Curie-Weiss law of pseudo block spins for ferroelectrics, we obtained the susceptibility for the lower and higher temperature approximations of the Brillouin function. According to our viewpoint, the state of dipole glass can be regarded as paraelectric ordering of pseudo block spins with higher temperature limit and lower temperature limit of the Brillouin function. For Rochelle salts, this phase may have ferroelectric and dipole glass mixed states where higher temperature limit and lower temperature limit and in the intermediate range between these a ferroelectric state happens.</P>
Patterns of Plasma Bullet in Plasma Jets
Gook Hee Han,Je Huan Koo,Duk In Choi,Eun Ha Choi,Guangsup Cho Institute of Electrical and Electronics Engineers 2015 IEEE transactions on plasma science Vol. No.
<P>Composite charges applied to plasma striations were investigated through this paper. Bullets in plasma jets stemming from effective electrons made up of a moving target electron with screening electrons and ions around it were assessed using an atom-like structure induced by an external electric or magnetic field. To maintain a zero total charge, screening electrons and ions were assumed to be spherically and symmetrically distributed around a target moving electron -e, and the surrounding -e or +e was equivalent to the composition of an electric field vortex and an electron. Electrons moving around a spherical orbit were found to have positive charges under a strong electric field but negative charges under a weak field, mainly because the cross-sectional area of the flux was very small. In plasma jets, striations are a phenomenon that may occur when charges gather in the presence of an electric or gauge field. A plasma striation can occur if the effective charge exceeds a critical value determined by setting the derivative of the effective charge to zero, but only if the electric field lines passing through the striation are connected.</P>
전하밀도파 이론으로 결정질 태양전지의 입사각에 따른 단락전류밀도 변화 연구
서일원,구제환,윤명수,조태훈,이원영,조광섭,권기청,Seo, Il Won,Koo, Je Huan,Yun, Myoung Soo,Jo, Tae Hoon,Lee, Won Young,Cho, Guang Sup,Kwon, Gi Chung 한국진공학회 2013 Applied Science and Convergence Technology Vol.22 No.4
광 입사각에 따른 태양전지의 양자효율을 전류의 출력으로 변환시켜 측정하였다. 기존의 태양전지의 원리는 태양전지가 태양광을 받았을 때 전자와 전공으로 분리되어 전류가 흐르게 된다는 것이었다. 그렇지만 저자들 중에 일부가 얼마 전에 태양전지원리를 새롭게 주장한 바 있다. 그 이론은 전하밀도파(charge density wave)들이 고정(pinning) 되었을 때, 이 고정 전위벽(pinning potential barrier)을 태양 광에 의해 넘을 수 있어서 전자 덩어리에 의한 전류 즉 단락전류($I_{SC}$)가 가능하다는 것이었다. 본 실험에서는 태양광의 입사각에 따른 태양전지의 단락전류밀도 ($J_{SC}$)를 측정하여 비교해본 결과 측정값들과 전하밀도파 이론과 매우 일치함을 보인다. We measure solar currents transformed from quantum efficiency as a function of incident angles of solar lights. According to conventional models for solar cells, solar currents can be induced when electrons are separated into electrons and holes in the presence of incident solar lights. On the contrary, solar currents can be possible at the time when pinned charge density waves go beyond the pinning potential barrier under the influence of incident solar beams suggested by some authors. In this experiment, measured solar currents and our theory are in good correspondence to confirm the angle dependence of solar lights.
대기압 플라즈마의 선택적 도핑 공정에서 온도에 의한 인(Phosphorus)의 확산연구
김상훈(Sang Hun KIM),윤명수(Myoung Soo Yun),박종인(Jong In Park),구제환(Je Huan Koo),김인태(In Tae Kim),최은하(Eun Ha Choi),조광섭(Guangsup Cho),권기청(Gi-Chung Kwon) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.5
In this study, we propose the application of doping process technology for atmospheric pressure plasma. The plasma treatment means the wafer is warmed via resistance heating from current paths. These paths are induced by the surface charge density in the presence of illuminating Argon atmospheric plasmas. Furthermore, it is investigated on the high-concentration doping to a selective partial region in P type solar cell wafer. It is identified that diffusion of impurities is related to the wafer temperature. For the fixed plasma treatment time, plasma currents were set with 40, 70, 120 mA. For the processing time, IR(Infra-Red) images are analyzed via a camera dependent on the temperature of the P type wafer. Phosphorus concentrations are also analyzed through SIMS profiles from doped wafer. According to the analysis for doping process, as applied plasma currents increase, so the doping depth becomes deeper. As the junction depth is deeper, so the surface resistance is to be lowered. In addition, the surface charge density has a tendency inversely proportional to the initial phosphorus concentration. Overall, when the plasma current increases, then it becomes higher temperatures in wafer. It is shown that the diffusion of the impurity is critically dependent on the temperature of wafers.
Plasma Diffusion Along a Fine Tube Positive Column
Guangsup Cho,Jung-Hyun Kim,Jong-Mun Jeong,Ha-Chung Hwang,Dong-Jun Jin,Je-Huan Koo,Eun-Ha Choi,Verboncoeur, J.P.,Han-Sup Uhm IEEE 2009 IEEE transactions on plasma science Vol.37 No.3
<P>The propagation velocity of light emission is observed to be u<SUB>p</SUB> ~0.92 times10<SUP>+5</SUP> m/s along a tube of an inner diameter r<SUB>o</SUB> ~1.5 times10<SUP>-3</SUP> m with an external electrode fluorescent lamp filled with 97% Ne and 3% Ar at a total pressure of 30 torr, a mercury-free lamp without phosphor coating the inside glass wall. The origin of this propagation is shown to be ambipolar diffusion with a plasma diffusion speed of u<SUB>p</SUB> ~ (4.8/r<SUB>o</SUB>)D<SUB>a</SUB> for diffusion coefficient D<SUB>a</SUB> along the positive column. When a high voltage magnitude is applied at the external electrode, a high-density plasma is generated inside the hollow electrode, and the plasma diffuses along the positive column toward the ground electrode.</P>
신명주,정종문,김정현,김가을,이미란,유동근,구제환,홍병희,최은하,조광섭,Shin, Myeong-Ju,Jeong, Jong-Mun,Kim, Jung-Hyun,Kim, Ga-Eul,Lee, Mi-Ran,Yoo, Dong-Gun,Koo, Je-Huan,Hong, Byoung-Hee,Choi, Eun-Ha,Cho, Guang-Sup 한국진공학회 2007 Applied Science and Convergence Technology Vol.16 No.5
유전 장벽 방전이 특징인 외부전극 형광램프(External Electrode Fluorescent Lamp, EEFL)에서 유리재의 유전 특성인 유전상수 K와 유전손실 tan ${\delta}$가 램프에 미치는 영향을 조사하기 위하여 4 종류의 유리관을 사용하였다. 종래 일반적으로 사용되는 Borosilicate 유리재는 유전상수 $K=5.6{\sim}5.9$이고 유전 손실 tan ${\delta}=5.0{\times}10^{-3}{\sim}6.0{\times}10^{-3}$이다. Aluminosilicatae는 K=6.6이고 유전손실이 작은 tan ${\delta}=1{\times}10^{-4}$이다. Soda-lime 유리관은 유전상수가 큰 K=7.7이고, 유전 손실이 매우 큰 tan ${\delta}=1.37{\times}10^{-2}$이다. 유전 상수 K가 크면 외부전극 자체의 캐패시터를 크게 하여 방전 효율이 증가한다. 그러나 유전 손실이 크면 외부전극 자체의 전력 소모로 인하여 효율 저하와 핀홀 발생의 원인이 된다. 높은 유전상수 및 낮은 유전손실의 Aluminosilicate 외부전극 형광램프는 종래의 Borosilicate 외부전극 형광램프에 비하여 휘도와 효율이 $12{\sim}20%$ 증가하고, 핀홀에 매우 강하다. 유전상수와 유전손실이 큰 Soda-lime 외부전극 형광램프는 효율이 다소 낮고, 핀홀에도 매우 취약하다. 따라서 외부전극 형광램프는 유전상수 K가 크고 유전손실 tan ${\delta}$가 작은 유리관이 최적이다. Influence of glass dielectric property (dielectric constant K, dielectric loss) on the external electrode fluorescent lamps of the dielectric barrier discharge has been investigated with 4-different glasses. Conventional borosilicate glass tubes with $K=5.6{\sim}5.9$ and tan ${\delta}=5.0{\times}10^{-3}{\sim}6.0{\times}10^{-3}$ and aluminosilicate glass tubes with high K=6.6 and low tan ${\delta}=1{\times}10^{-4}$ and soda-lime glass tribes with K=7.7 and tan ${\delta}=1.37{\times}10^{-2}$ have been compared. The high value of dielectric constant K makes the capacitance of external electrode fluorescent lamps intensity and enhances the discharge efficiency. The dielectric loss of tan ${\delta}$ shows the factor of power consumption in the external electrode to induce heats and to be weak in pinhole stability. The aluminosilicate glass tubes of high K and low tan ${\delta}$ have been enhanced by $14{\sim}18%$ in luminance and efficiency in comparison with the conventional borosilicate glass tubes and the aluminosilicate external electrode fluorescent lamps are strong against the pinhole formation. Soda-lime glass tubes with high K and high tan ${\delta}$ are a little favorable in luminance and efficiency and they are very weak in pinhole occurrence.