• Progress in Superconductivity
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• 제2권2호
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• pp.71-75
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• 2001

The effect of annealing step-edges of LaAlO$_3$ and MgO single crystal substrates on YBa$_2$Cu$_3$O$_{7}$ junction has been studied. The step-edge was fabricated by argon ion milling and was annealed at 105$0^{\circ}C$ in 1 attn oxygen pressure. We compared AFM image near step-edge of the substrates between before and after annealing process. And YBa$_2$Cu$_3$O$_{7}$ thin film was deposited on the step-edge by a standard pulsed laser deposition. The step-edge junctions were characterized by current-voltage curves at 77 K. The annealing of step-edges of MgO substrate improved the current-voltage characteristic of Josephson junction: double steps in the current-voltage characteristic disappeared. However the annealing for LaAlO$_3$ did not improve the junction property.rty.

• Progress in Superconductivity
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• 제3권1호
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• pp.60-64
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• 2001

We have studied properties of step-edge Junction prepared with crystal orientation of sapphire substrate. The Step on sapphire substrates fabricated by conventional photolithography method and Ar ion milling method. $CeO_2$ buffer layer and in-situ YBCO thin film were deposited on the stepped sapphire substrates by a pulsed laser deposition method with the predetermined optimized condition. The step angle was centre fled low angle of about $25^{\circ}$. The YBCO film thickness was varied to obtain various thickness ratios of the film to the step height in a range from 0.7 to 1.2. I-V curves of junction were showed RSJ-behavior, double junction structure, and hysteresis due to the crystal orientation of substrate.

• Progress in Superconductivity
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• 제2권2호
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• pp.81-85
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• 2001

Uniformity of critical currents of YBa$_2$Cu$_3$O$_{7}$ step-edge Josephson junctions on SrTiO$_3$(100) substrates have been studied at various step-line angles. 15 identical junctions were made in series on each substrate that has a long straight step-edge line. Step-line angles studied were 0$^{\circ}$, 15$^{\circ}$, 30$^{\circ}$, and 45$^{\circ}$with respect to the crystal major axes of the substrate. Scattering of junction critical currents among the junctions on the same substrate increased with the step-line angle. Current-voltage curves showed standard resistively-shunted-junction (RSJ) characteristics in most of the 0$^{\circ}$junctions. However, the number of junctions showing RSJ behavior decreased with increasing step-line angle. Variations of detailed microstructure of the step-edge among junctions, which are coupled with the d-wave symmetry of YBa$_2$Cu$_3$O$_{7}$, are believed to be the main cause for the nonuniformity in the critical current.ent.

• Journal of Advanced Marine Engineering and Technology
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• 제24권2호
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• pp.82-89
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• 2000

에지검출은 영상인식의 첫 단계임을 동시에 영상인식의 성능을 좌우하는 아주 중요한 단계이다. 기존의 기울기연산자나 표면접합에 의한 에지검출과 달리 본 논문에서는 에지의 영역정보를 이용한 에지검출 알고리즘을 제시한다. 먼저 에지의 적합한 위치, 에지의 두께 그리고 에지의 길이에 대한 정의를 제시하고, 제시된 에지정의를 기본으로한 12개의 에지검출 윈도우와 알고리즘을 제안하였다. 제안된 12개의 윈도우는 모든 형태의 에지를 추출할 수 있는 에지검출윈도우로써 일반적으로 많이 사용되고 있는 기울기 연산자나 0점교차 연산자인 LoG 연산자보다 좋은 에지검출 성능을 보여 주었다.

• 한국재료학회지
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• 제9권1호
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• pp.86-91
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• 1999

(001) $\textrm{SrTiO}_3$(STO) 기판위에 고온초전도 $\textrm{YBa}_{2}\textrm{Cu}_{3}\textrm{O}_{7-x}$(YBCO)박막을 이용한 계단형 모서리 임계접합을 제조하였다. STO (100) 단결정 기판위에 계단형 모서리(step-edge)를 제작하기 위한 이온밀링 마스크로 plasma enhanced chemical vapor deposition방법으로 증착된 diamond-like carbon (DLC) 박막을 사용하였고, oxygen reactive ion etch 방법으로 건식식각하였다. 이렇게 제작된 계단형 모서리 기판위에 c-축 수직한 YBCO 박막과 STO박막을 pulsed laser deposition방법으로 에피텍셜하게 증착하였다. 계단의 상층과 하층에서 모두 임계가 형성되었으며 이 접합의 임계온도는 77 K 이상이었고 16K에서 $\textrm{I}_{c}\textrm{R}_{n}$products가 7.5mV, 77 K에서 0.3mV의 값을 나타내었다. 이들 전류-전압 특성은 two noisy resistively shunted Josephson junction 모델을 잘 만족하였다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.147-151
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• 1999

YBCO step-edge Josephson junction were fabricated on sapphire substrates. The steps were formed on R-plane sapphire substrates by using Ar ion milling with PR masks. The step angle was controlled in the wide range from 25$^{\circ}$ to 50$^{\circ}$ by adjusting both the Ar ion incident angle and the photoresist mask rotation angle relative to the incident Ar ion beam. CeO$_2$ buffer layer and in-situ YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) thin films was deposited on the stepped R-plane sapphire substrates by pulsed laser deposition method. The YBCO film thickness was varied to obtain the ratio of film thickness to step height in the range from 0.5 to 1. The step edge junction exhibited RSJ-like behaviors with I$_cR_n$ product of 100 ${\sim}$ 300 ${\mu}$V, critical current density of 10$^3$ ${\sim}$ 10$^5$ A/ cm$^2$ at 77 K.

• Progress in Superconductivity
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• 제5권2호
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• pp.94-97
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• 2004

Step-edge Josephson junctions (SEJ) have been fabricated on sapphire substrates with in situ deposited films of CeO$_2$ buffer layer and YBa$_2$Cu$_3$O$_{7}$ films on the low angle steps. Direct coupled SQUID magnetometers with the SEJ were formed on 1 cm X 1 cm R-plane sapphire substrates. Typical 5-${\mu}{\textrm}{m}$-wide Josephson junctions have R$_{N}$ of 3 Ω and I$_{c}$ of 50 $mutextrm{A}$ at 77 K. The direct coupled SQUID magnetometers were designed to have pickup coils of 50-${\mu}{\textrm}{m}$-wide 16 parallel loops on the 1 cm X 1 cm substrates with outer dimension of 8.8 mm X 8.8 mm. The SEJ SQUID magnetometers exhibit relatively low 1/f noise even with dc bias control, and could be stably controlled by flux-locked loops in the magnetically disturbed environment. Field noise of the do SQUID was measured to be 200∼300 fT/Hz$^{1}$2/in the white noise region and about 2 pT/Hz$^{1}$2/ at 1 Hz when measured with dc bias method.hod.d.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.83-86
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• 1999

We have fabricated $_2Cu_3O_7$ step-edge junctions with different step orientations and studied their transition properties. Steps with different orientations were prepared on the substrate. Josephson junctions were made on a single substrate with step orientations ranging from 0$^{\circ}$ to 165$^{\circ}$ at 15$^{\circ}$ interval. We measured current-voltage characteristics, the critical current, and the superconducting transition temperature as a function of the angle. The critical current showed a modulation that has a maximum near 0$^{\circ}$ or 90$^{\circ}$ and a minimum near 45$^{\circ}$ and 135$^{\circ}$. We believe that the critical current modulation with the step orientation could be associated with the symmetry of high T$_c$ superconductor.

• 한국재료학회지
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• 제8권10호
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• pp.950-955
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• 1998

Ar 이온 식각법을 이용하여 (001) SrTiO3(STO) 단결정 기판 위에 200nm 높이의 계단형 모서리를 제작하였다. 계단식은 입사하는 Ar 이온 빔에 대한 Ar 이온 입사각과 마스크 회전각을 조절함으로써 38$^{\circ}$-70$^{\circ}$의 넓은 범위로 제어할 수 있었다. 초전도 YBa2Cu3O7-$\delta$박막은 계단이 있는 STO 기판 위에 펄스레이저 증착법을 이용하여 증착하였으며, 박막의 두께는 계단 높이에 대한 박막의 두께비가 0.5-1.2가 되도록 하였다. 계단형 모서리 조셉슨 접합의 임계전류밀도와 IcRn값은 77K에서 각각 104A/$\textrm{cm}^2$, 70-200$\mu$V이었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.155-159
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• 2000

YBCO step-edge dc SQUID magnetometers on sapphire substrates have been fabricated. CeO2 buffer layer and YBCO films were deposited in situ on the low angle (${\sim}$35$^{\circ}$) steps formed on the sapphire substrates. Typical 5-${\mu}$m-wide junction has R$_n$ of 5 ${\omega}$ and I$_c$ of 50 ${\mu}$A with large I$_c$R$_n$ product of 250 ${\mu}$V at 77K. According to applied bias current, depth of voltage modulation was changed and maximum voltage was measured 16 ${\mu}$V. Field noise of do SQUID was measured 100${\sim}$300 fT/${\surd}^{Hz}$ in the 1 $^{kHz}$, and about 1.5 pT/${\surd}^{Hz}$ in the 1/f region. For ac bias reversal method, field noise was decreased in the 1/f region. The QRS peak of magnetocardiogram was measured 50 pT in the magnetically shielded room.