• E2M - 전기 전자와 첨단 소재
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• 제10권8호
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• pp.813-818
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• 1997

In this study the thin film air core and magnetic core inductors consisting of planar coil and/or CoNbZr amorphous magnetic layers on a Si substrate were fabricated as spiral type by using rf magnetron sputtering and wet etching methods. The etchant solution was achieved by iron chloride solution(17.5 mol%) mixed with HF (20 mol%) during 150 sec which etched Cu films and CoNbZr/Cu/CoNbZr multi-layer films. They were about 10${\mu}{\textrm}{m}$ of thickness and 10$\times$10 mm$^2$of size. The properties of thin film magnetic core inductor were 400 nH of Q value at 10 MHz and the resonance frequency was about 300 MHz.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.257-265
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• 2021

In this study, we report niobium (Nb) with hierarchical porous structure produced by a one-pot, HF-free electrochemical etching process. It is proved experimentally that a well-defined hierarchical porous structure is produced from the combination of a limited repetition of pulse etching and high concentration of aggressive anion (i.e., SO₄^2-), which results in hierarchical pores with high order over 3. A formula is derived for the surface area of porous Nb as a function of the hierarchical order of pores while the experimental surface area is estimated on the basis of the electrochemical gas evolution rate on porous Nb. From the comparison of the theoretical and experimental surface areas, an in-depth understanding was gained about porous structure produced in this work in terms of the actual pore shape and hierarchical pore order.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.138-138
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• 2003

광대역 LiNbO$_3$ 광변조기의 초고속 광 변조 구현을 위해서는 RF/ optical 속도 정합 및 임피던스 매칭 조건 하에서 낮은 구동전압을 얻을 수 있는 ridge 구조의 제작이 필수적이며 이런 구조 제작하기 위해서는 식각 속도와 식각면 거칠기 식각 profile 및 식각 과정에서의 반응물의 감소 등과 같은 개선을 위한 연구가 필요하다. 본 연구에서는 LiNbO$_3$ 기판 위에 메탈 마스크를 형성한 후 비등방성 (anisotropic) 건식 식각 방법인 NLD (Neutral Loop Discharge)로 플라즈마 식각을 하였다. NLD plasma 식각은 1Pa 이하의 압력에서 낮은 전자 온도를 갖는 고밀도 플라즈마를 생성하고 이온 플라즈마를 형성하여 LiNbO$_3$ 표면의 원자와 분자를 이온충돌효과를 이용하여 물리적인 식각과 discharge로 형성된 레디칼 (radical)과의 상호작용에 의한 화학적 식각 메커니즘에 의한 방법으로 plasma에 의한 시편의 손상이 적으며 식각 속도가 또한 높은 것이 특징이다. 본 논문에서는 안테나 파워와 가스의 유량에 따른 LiNbO$_3$ 식각 profile 특성에 관하여 연구 하고자 한다.

• Progress in Superconductivity
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• 제3권1호
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• pp.49-55
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• 2001

Josephson junction arrays were fabricated by DC magnetron sputtering, self-aligning and reactive ion etching technique. The Al native oxide, formed by thermal oxidation, was used as the tunneling barrier of Nb/$Al-A1_2$$O_3$Nb trilayer. The arrays have 2,000 Josephson junctions with the area of $14\mu\textrm{m}$ $\times$ $46\mu\textrm{m}$. The gap voltages were in the range of 2.5 ~2.6 mV and the spread of critical current was $\pm$11~14%. When operated at 70~94 ㎓, the arrays generated zero-crossing steps up to 2.1~2.4 V. To improve transmission of microwave power and prevent diffusion of oxygen into Nb ground-plane while depositing $SiO_2$dielectric, we applied a plasma nitridation process to the Nb ground-plane. The microwave power was well propagated in Josephson junction arrays with nitridation. The difference in microwave transmission 7an be interpreted by the surface impedance change depending on nitridation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.141-145
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• 1997

스퍼터링법으로 제조한 CoNbZr/Cu/CoNbZr 다층막에 대해 습식 식각법으로 패턴을 형성하기 위해 새로운 식각 용액을 제조하여 이 용액의 최적의 식각 조건에 대해 연구하였다. 염기성 수용액은 농도에 관계없이 Cu만을 선택적으로 식각하며 CoNbZr 비정질 박막은 식각하지 않았다. 그러나, 본 연구에서 제조 한 17.5 mol%의 염기성 수용액에 HF를 20 mol% 혼합한 식각 용액으로 CoNbZr/Cu/CoNbZr 다층막을 동시에 식각할 수 있었다. 또한 이 식각 용액은 CoNbZr/Cu/CoNbZr 다층막을 3단계로 식각하고 식각된 단면은 이방성 구조를 가지며, 매우 우수한 식각 특성을 나타내었다.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.20-25
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• 2018

Niobium nitride (NbN) superconducting thin films with the thickness of 100 and 400 nm have been deposited on the surfaces of silicon oxide/silicon substrates using a sputtering method. Their superconducting properties have been evaluated in terms of the transition temperature, critical magnetic field, and critical current density. In addition, the NbN films were patterned in a line with a width of $10{\mu}m$ by a reactive ion etching (RIE) process for their characterization. This study proves the applicability of the standard complementary metal-oxide-semiconductor (CMOS) process in the fabrication of superconducting thin films without considerable degradation of superconducting properties.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.145.1-145
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• 2003

• 한국세라믹학회지
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• 제26권5호
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• pp.661-669
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• 1989

The defect structure in LiNbO3 single crystals grown by Czochralski method from the congruently melting composition were investigated. Chemical etching patterns were studied in x-plane, z-plane, and major cleavage plane, respectively, dislocation density was higher at the periphery of crystals than at the center because the thermal stress due to radial temperature gradient had a main effect on it, as compared with dislocations formed from the solid-liquid interface. Many dislocation lineages were arranged along several directions.

• 한국세라믹학회지
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• 제42권11호
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• pp.749-752
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• 2005

When an electric field higher than a characteristic coercive field is applied to a ferroelectric such as $LiNbO_3$, the orientation of the spontaneous polarization is reversed, which causes the reversal of the sign of odd-rank tensor properties such as electro-optic and nonlinear optic coefficients. A fabrication process of insulator and periodic external field assisted poling of a z-cut $LiNbO_3$ have been optimized for a periodic $180^{\circ}$ phase inversion along z-axis. The poling jig and the poling control system, fully controlled by a computer, for high quality and reproducible PPLN fabrication have been devised. Periodically polarization reversed PPLN was adjusted based on the fabricated thickness of insulator. The poling structure of PPLN was observed under a microscope after etching PPLN samples by an etching solution ($HF:HNO_3$ = 1 : 2) for about 15 min.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.123-126
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• 2002

Samples of Nb/Al-Al$O_{x}$/Nb tunnel junction with the size of 50$\mu$m $\times$ 50$\mu$m were fabricated by employing self-aligning and reactive ion etching technique. In the samples with high-quality, $V_{m}$ value (the product of the critical current and subgap resistance measured at 2 mV) was 34 mV at the critical current density $J_{c}$ = 500 A/$cm^{2}$ and $V_{g}$ value (the gap voltage) was 2.8 mV. In the higher $J_{c}$, voltage fluctuation in the current rising at the gap voltage was observed. The $V_{m}$ and $J_{c}$ value were 8 mV and 900 A/$cm^{2}$, respectively.