• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.95.1-95.1
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• 2010

Transparent conducting ZnO films were deposited to apply DSSC Substrate on glass substrates at $500^{\circ}C$ by ionbeam-assisted deposition. Crystallinity, microstructure, surface roughness, chemical composition, electrical and optical properties of the films were investigated as a function of deposition parameters such as ion energy, and substrate temperature. The microstructure of the polycrystalline ZnO films on the glass substrate were closely related to the oxygen ion energy, arrival ratio of oxygen to Zinc Ion bombarded on the growing surface. The main effect of energetic ion bombardment on the growing surface of the film may be divided into two categories; 1) the enhancement of adatom mobility at low energetic ion bombardment and 2) the surface damage by radiation damage at high energetic ion bombardment. The domain structure was obtained in the films deposited at 300 eV. With increasing the ion energy to 600 eV, the domain structure was changed into the grain structure. In case of the low energy ion bombardment of 300 eV, the microstructure of the film was changed from the grain structure to the domain structure with increasing arrival ratio. At the high energy ion bombardment of 600 eV, however, the only grain structure was observed. The electrical properties of the deposited films were significantly related to the change of microstructure. The films with the domain structure had larger carrier concentration and mobility than those with the grain structure, because the grain boundary scattering was reduced in the large size domains compared with the small size grains. The optical transmittance of ZnO films was dependent on a surface roughness. The ZnO films with small surface roughness, represented high transmittance in the visible range because of a decreased light surface scattering. By varying the ion energy and arrival ratio, the resistivity and optical transmittance of the films were varied from $1.1{\times}10^{-4}$ to $2.3{\times}10^{-2}{\Omega}cm$ and from 80 to 87%, respectively. The ZnO film deposited at 300 eV, and substrate temperature of $500^{\circ}C$ had the resistivity of $1.1{\times}10^{-4}{\Omega}cm$ and optical transmittance of 85% in visible range. As a result of experiments, we provides a suggestition that ZnO thin Films can be effectively used as the DSSC substrate Materials.

• 한국진공학회지
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• 제9권2호
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• pp.155-161
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• 2000

이온빔보조증착법을 이용하여 c-BN(70%)/h-BN(30%) 혼합막을 합성하였으며, 이를 후속 열처리로 안정화 시켰다. 보론은 e-beam evaporator로, 질소는 end-hall type 이온 건으로 공급하였으며, 기판에는 -400과 -500V의 DC 바이어스를 각각 인가하였고, $700^{\circ}C$로 가열하였다. 보론의 기화속도는 1.2 $\AA$/sec였고, 질소이온의 에너지는 약 100 eV였다. 막 합성 후같은 진공에서 후속열처리를 $700^{\circ}C$ 및 $800^{\circ}C$에서 1시간동안 각각 행하였다. 후속열처리를 하지 않은 경우에는 공기 중에 노출된 직후에 막이 기판에서 박리된 반면, $800^{\circ}C$에서 후속 열처리를 한 경우에는 안정하였다. 후속 열처리에 의하여 막 전체의 응력은 4.9 GPa에서 3.4 GPa로 감소하였으나, c-BN상의 응력은 변화하지 않았다. 이러한 결과는 c-BN상의 응력 해소를 주요 안정화 기구로 보고한 기존의 결과와 다른 것으로, 후속 열처리 동안에, 비정질이나 결함이 많은 h-BN상의 구조적, 화학적 relaxation에 의하여 막의 안정화가 진행될 수 있음을 의미한다. c-BN상의 분율이 작은 혼합막의 경우 비 c-BN상의 안정화가 막 전체의 안정화에 매우 중요할 것으로 판단된다.

• 한국초전도ㆍ저온공학회논문지
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• 제15권2호
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• pp.34-38
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• 2013

AC Losses for face to face stacks of four identical coated conductors (CCs) were numerically calculated using the H-formulation combined with the E-J power law and the Kim model. The motive sample was the face to face stack of four 2 mm-wide CC tapes with 2 ${\mu}m$ thick superconducting layer of which the critical current density, $J_c$, was $2.16{\times}10^6A/cm^2$ on IBAD-MgO template, which was suggested for the mitigation of ac loss as a round shaped wire by Korea Electrotechnology Research Institute. For the calculation the cross section of the stack was simply modeled as vertically aligned 4 rectangles of superconducting (SC) layers with $E=E_o(J(x,y,t)/J_c(B))^n$ in x-y plane where $E_o$ was $10^{-6}$ V/cm, $J_c$(B) was the field dependence of current density and n was 21. The field dependence of the critical current of the sample measured in four-probe method was employed for $J_c$(B) in the equation. The model was implemented in the finite element method program by commercial software. The ac loss properties for the stacks were compared with those of single 4 cm-wide SC layers with the same critical current density or the same critical current. The constraint for the simulation was imposed in two different ways that the total current of the stack obtained by integrating J(x,y,t) over the cross sections was the same as that of the applied transport current: one is that one fourth of the external current was enforced to flow through each SC. In this case, the ac loss values for the stacks were lower than those of single wide SC layer. This mitigation of the loss is attributed to the reduction of the normal component of the magnetic field near the SC layers due to the strong expulsion of the magnetic field by the enforced transport current. On the contrary, for the other case of no such enforcement, the ac loss values were greater than those of single 4cm-wide SC layer and. In this case, the phase difference of the current flowing through the inner and the outer SC layers of the stack was observed as the transport current was increased, which was a cause of the abrupt increase of ac loss for higher transport current.

• Progress in Superconductivity
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• 제13권1호
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• pp.7-11
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• 2011

조성경사법을 이용하여 LMO/IBAD-MgO template 상에 EDDC 증착법을 이용하여 $Sm_{1+x}Ba_{2-x}Cu_{3+y}O_{7-d}$ 초전도 박막을 증착하였다. 테이프 형상의 기판상에 길이방향으로 $Sm_{1+x}Ba_{2-x}Cu_{3+y}O_{7-d}$ 박막의 조성비가 연속적으로 변하는 샘플을 얻을 수 있었고, 비접촉 Hallprobe를 이용하여 임계전류를 측정한 결과 조성비에 대응하는 연속적인 임계전류분포를 측정할 수 있었다. 본 조성비 영역 중 Sm:Ba:Cu = 1.01:1.99 :4.87의 조성비에서 최대의 임계전류를 보였다. 이 조성비에서 SmBCO 박막표면에 전체적으로 roof tile 형상의 결정립들이 관찰되었으며 국소적으로 2차상들이 관찰되었다. 조성 경사법을 이용하면 광범위한 조성비영역에서 신뢰도 높은 초전도특성, 결정배향성, 박막표면 형상 등을 조사할 수 있을 것으로 예상된다.

• Journal of Periodontal and Implant Science
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• 제38권sup2호
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• pp.373-384
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• 2008

Purpose: The aim of this study is to compare the healing response of various Hydroxyapatite(HA) coated dental implants by Ion-Beam Assisted Deposition(IBAD) placed in the surgically created circumferential gap in dogs. Materials and methods: In four mongrel dogs, all mandibular premolars and the first molar were extracted. After an 8 weeks healing period, six submerged type implants were placed and the circumferential cylindrical 2mm coronal defects around the implants were made surgically with customized step drills. Groups were divided into six groups : anodized surface, anodized surface with 150nm HA and heat treatment, anodized surface with 300nm HA and heat treatment, anodized surface with 150nm HA and no heat treatment, and anodized surface with 150nm HA, heat treatment and bone graft, anodized surface with bone graft. The dogs were sacrificed following 12 weeks healing period. Specimens were analyzed histologically and histomorphometrically. Results: During the healing period, healing was uneventful and implants were well maintained. Anodized surface with HA coating and $430^{\circ}C$ heat treatment showed an improved regenerative characteristics. Most of the gaps were filled with newly regenerated bone. The implant surface was covered with bone layer as base for intensive bone formation and remodeling. In case that graft the alloplastic material to the gaps, most of the coronal gaps were filled with newly formed bone and remaining graft particles. The bone-implant contact and bone density parameters showed similar results with the histological findings. The bone graft group presented the best bone-implant contact value which had statistical significance. Conclusion: Within the scope of this study, nano-scale HA coated dental implants appeared to have significant effect on the development of new bone formation. And additional bone graft is an effective method in overcoming the gaps around the implants.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.3-3
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• 2009

In order to investigate the possibility of using mixed rare earth $(Nd_{1/3}Eu_{1/3}Gd_{1/3})Ba_2Cu_3O_{7-x}$ (NEG123) as the superconducting layer of the HTS coated conductor, the NEG123 thin film was deposited epitaxialy on LAO(100) single crystal and IBAD_YSZ metal templates by pulsed laser deposition. Systematic studies were carried out to investigate the influences of deposition parameters of PLD on the micro structure, texture and superconducting properties of NEG-123 coated conductor. Deposition at oxygen partial pressure of 600 mTorr was needed to routinely obtain high quality NEG123 films with $J_c$'s (77K) over 2 MA/$cm^2$ and Tc's over 90K (${\Delta}T{\sim}2\;K$). We verified from magnetization study that the NEG123 has an improved in-field Jc as the field increases at temperatures between 10 K and 77 K compared with Gd123. The $J_c$ (77K, self field) and the value of onset $T_c$ of NEG123 thin film on LAO substrate was $4.0MA/cm^2$ and 92K, respectively. This is the first report, to the best of our knowledge, of coated conductors with NEG123 film as the superconducting layer which have Ic and Jc over 40 A/cm-width and 1.6 MA/$cm^2$ at 77K, self field. This study shows the possibility of using NEG123 film as the superconducting layer of the HTS coated conductor which can be used in high magnetic field power electric devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.299-299
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• 2008

초전도 응용기기 개발을 위해 필수적인 초전도 박막선재는 길이방향으로 임계전류밀도가 균일한 것이 요구되고 있다. 전체 길이에 대해 가장 임계전류 밀도가 낮은 지점에서 선재의 특성이 제한되기 때문이다. 한편 초전도 박막선재의 경우 높은 임계전류 밀도와 함께 과전류 등의 사고발생시를 고려하여 안정화재를 반드시 초전도층 위에 구성하여야 한다. 고가의 은(Ag)을 두껍게 증착할 수 없으므로 보통은 구리도금 또는 솔더링으로 안정화재를 덧댄다. 본 연구에서는 초전도 박막선재의 대전류화와 길이방향의 전류 균일성 향상, 안정화 특성 항상 등의 목적으로 초전도 박막선재간 확산 접합을 시도하였다. 초전도 박막선재 제조 후 안정화재인 은을 증착 후 따로 구리도금이나 솔더링 없이 선재 2가닥을 서로 포개어서 열처리를 하였다. 이때 선재간의 충분한 확산접합을 위하여 선재를 둥근 SUS 디스크에 감고 외부에 다시 SUS판재로 감아서 열처리 도중 압력을 가하였다. 아울러 포개는 방법도 초전도층의 위치에 따라 3 가지로 하였으며 열처리 후 임계전류를 측정하였다. 각 선재한 가닥에 대한 임계전류는 77K에서 50~60 A 정도의 임계전류를 나타내었으며 선재를 접합한 경우 90~120A의 특성을 나타내었으며 특히 초전도층이 설마주보는 형태에서 가장 높은 임계전류 특성을 나타내었다.