• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.543-543
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• 2013

Thin-film transistors (TFTs) based on oxide semiconductors have been regarded as promising alternatives for conventional amorphous and polycrystalline silicon TFTs. Oxide TFTs have several advantages, such as low temperature processing, transparency and high field-effect mobility. Lots of oxide semiconductors for example ZnO, SnO2, In2O3, InZnO, ZnSnO, and InGaZnO etc. have been researched. Particularly, zinc-tin oxide (ZTO) is suitable for channel layer of oxide TFTs having a high mobility that Sn in ZTO can improve the carrier transport by overlapping orbital. However, some issues related to the ZTO TFT electrical performance still remain to be resolved, such as obtaining good electrical contact between source/drain (S/D) electrodes and active channel layer. In this study, the bottom-gate type ZTO TFTs with staggered structure were prepared. Thin films of ZTO (40 nm thick) were deposited by DC magnetron sputtering and performed at room temperature in an Ar atmosphere with an oxygen partial pressure of 10%. After annealing the thin films of ZTO at $400^{\circ}C$ or an hour, Cu, Mo, ITO and Ti electrodes were used for the S/D electrodes. Cu, Mo, ITO and Ti (200 nm thick) were also deposited by DC magnetron sputtering at room temperature. The channel layer and S/D electrodes were defined using a lift-off process which resulted in a fixed width W of 100 ${\mu}m$ and channel length L varied from 10 to 50 ${\mu}m$. The TFT source/drain series resistance, the intrinsic mobility (${\mu}i$), and intrinsic threshold voltage (Vi) were extracted by transmission line method (TLM) using a series of TFTs with different channel lengths. And the performances of ZTO TFTs were measured by using HP 4145B semiconductor analyzer. The results showed that the Cu S/D electrodes had a high intrinsic field effect mobility and a low effective contact resistance compared to other electrodes such as Mo, ITO and Ti.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.935-940
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• 1997

This study investigated the crystallization behavior in PbO-ZnO-B2O3-TiO2 system sealing glass, inorganic polymer heat-treated by conventional heat and microwave energy. After determining heat-treated temperature for crystallization and characteristic points by DTA analysis, samples were heat-treated in a classical electric furnace and a home-style microwave oven (LG Electronic Co., 2.45 GHz, 700 W). A microwave heat-treated sample had the growth of PbTiO3 crystal at 45$0^{\circ}C$, 2$0^{\circ}C$ lower than that of a conventionally heat-treated sample. Also, it had crystallinity about 20% higher than the conventionally heat-treated sample. At 49$0^{\circ}C$, the size of PbTiO3 crystal in the conventionally heat-treated sample was larger than that in the microwave heat-treated sample due to longer heat-treated time.

• Korean Journal of Materials Research
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• v.7 no.10
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• pp.872-876
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• 1997

(1-x)CaTi $O_{3}$-xLa(Z $n_{1}$2/ $Ti_{1}$2/) $O_{3}$의 마이크로 유전특성을 조사하였다. x가 증가함에 따라 비유전율과 공진주파수의 온도계수는 감소하였으며, Qㆍ $f_{0}$는 증가하였다. 그 결과 x=0.5인 (C $a_{0.5}$L $a_{0.5}$)( $Ti_{0.75}$Z $n_{0.25}$) $O_{3}$의 조성에서 $\varepsilon$$_{r}$=51, Qㆍ $f_{0}$=38,000 (at 7 GHz), $\tau$$_{f}$=+5ppm/$^{\circ}C$의 유전특성이 나타났다. (C $a_{0.5}$L $a_{0.5}$)( $Ti_{0.75}$Z $n_{0.25}$) $O_{3}$조성의 소결온도를 저하시키기 위하여 B $i_{2}$ $O_{3}$를 주조성으로한 소결체를 첨가하여 소결 및 유전특성을 조사하였다. 1wt% 0.76B $i_{2}$ $O_{3}$-0.24NiO가 첨가된 경우 소결온도는 15$0^{\circ}C$ 낮아졌으며, 비유전율 ($\varepsilon$$_{r}$), 공진주파수의 온도계수($\tau$$_{f}$), Qㆍ $f_{0}$가 각각 50+5ppm/$^{\circ}C$, 35,000인 마이크로파 유전특성이 얻어졌다. 또한 3wt%의 0.76B $i_{2}$ $O_{3}$-0.24NiO가 첨가된 경우 소결온도는 20$0^{\circ}C$ 저하되었고, 비유전율 ($\varepsilon$$_{r}$)과 공진주파수의 온도계수 ($\tau$$_{f}$)는 변하기 않았으나, Qㆍ $f_{0}$값이 38,000에서 25,000으로 저하되었다. 25,000으로 저하되었다.되었다.되었다.되었다.

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.829-835
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• 1989

Devitrifing solder glasses in a specific group of glass ceramic materials are extensively used in hermetically sealing alumina electronics packages. Preferred frit glass compositions of this study consist of 37~40wt% PbO, 35~40wt% ZnO, 18~20wt% B2O3, 1~3wt% SiO2, 0~6wt% TiO2. The coated frit glasses crystallize during firing and form a strong hermetic seal. DTA and X-ray diffraction were used to characterize crystallization of the glass frit. Frit seal containing 2wt% TiO2 has crystallization temperature of 550~57$0^{\circ}C$ with surface nucleation. Frit seal containing 6wt% TiO2 has crystallization temperature of 515~5$25^{\circ}C$ with bulk nucleation, and the main crystalline phase was perovskite lead titanate having minus expansion coefficient. The average activation energy for the crystallization calculated from Ozawa equation was 65$\pm$10kcal/mol.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.17-17
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• 2003

Semiconductors with ferromagnetism at room temperature has been actively searched for in recent years; a prospect of devices using both charge and spin continuously gives impetus to the activities. Transition metal doped oxide materials have been of particular interest. Co substituted ZnO [1] and TiO$_2$ [2] thin films, for example, were reported to show ferromagnetic properties at room temperature. However, various studies do not seem to converge on a definite picture [3,4,5]. The issue is rather fundamental: whether a system shows ferromagnetic properties at all, and in case it does, whether the system possesses a close coupling between magnetism and transport properties. In this talk, we shall assess the current status of transition metal doped oxide materials as room temperature ferromagnetic semiconductors.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.70-70
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• 2011

차세대 저항 메모리로 활용 가능한 ZnO 박막의 저항 변화 특성을 평가하였다. ZnO 박막은 Pt/Ti/SiO2/Si 기판 위에 스퍼터링 시스템을 이용하여 약 50nm 두께로 증착되었다. 증착된 박막에 전극을 evaporator를 이용하여 패턴닝 함으로써 전극-반도체-전극 구조의 소자를 만들고 전기적 특성을 평가하였다. 비교적 높은 compliance current (이하Icomp)를 설정한 경우 unipolar 저항 변화특성을 나타낸 데 비해 비교적 낮은 Icomp를 설정한 경우 bipolar 저항 변화특성을 나타내었다. 두 서로 다른 저항 변화 특성은 100cycle 이상 안정적으로 재현성 있게 나타났으며 이때의 저항비는 약 $10^3$ 정도를 나타냈다. 본 결과를 바탕으로 필라멘트 이론에 기초한 저항 변화 메커니즘을 설명하는 모델이 제시되었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.413-416
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• 1996

The ceramic dielectrics were fabricated by mixing of Mn $O_2$ and ZnO at (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_3$ and studied for dielectric relaxation characteristics. The dielectric relaxation time was increased by space charge polarization of palaelectric layer at the low temperature and frequency but it was decreased by Interface polarization at the high temperature and frequency. The remnant polarization and coercive field of ceramic dielectrics was decreased by rising temperature.ure.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.68-68
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• 2010

Electroluminescence (EL) characteristics of green-emission ZnS:Cu,Cl-based ac-type inorganic powder electroluminescent structures were examined by inserting carbon nanotubes (CNTs) into or next to the dielectric layer. For the top-emission type EL structure, where the luminescent light was emitted from the top of the structure, was fabricated by assembling in order, a top electrode, an emitting layer, a dielectric layer, and a bottom electrode from the top. $BaTiO_3$ powder mixed with CNTs was used as a dielectric layer or CNTs were deposited between the bottom electrode and $BaTiO_3$ dielectric layer in order to improve the role of the dielectric layer in the structure. Luminance of an EL structure with CNTs inclusion was greatly enhanced possibly due to the high dielectric constant in the dielectric layer of $BaTiO_3$/CNTs, which is one of hot research topics utilizing nano-objects for intensifying dielectric constant and reducing dielectric loss at the same time. A variation on the CNTs themselves and their inclusion methods in the dielectric layer has been exhorted, and the underlying mechanism for the role of CNTs in the EL structure will be explained in the poster. In order to extend the flexibility of EL devices, EL devices were fabricated on the paper substrate and their performance was compared other EL devices on the plastic-based substrate.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.54.1-54.1
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• 2010

산화물 기반의 TFT는 유리, 금속, 플라스틱 등 기판 종류에 상관없이 균일한 제작이 가능하며, 상온 및 저온에서 대면적으로 제작이 가능하고, 저렴한 비용으로 제작 가능하다는 장점 때문에 최근 많은 연구가 이루어지고 있다. 현재 TFT 물질로 많이 연구되고 있는 산화물은 ZnO (3.4 eV)나 InOx (3.6 eV), GaOx (4.9 eV), SnOx(3.7 eV)등의 물질과 각각의 조합으로 구성된 재료들이 주로 사용되고 있으며, 가장 많은 연구가 이루어진 ZnO 기반의 TFT는 mobility와 switching 속도에서 우수한 특성을 보이나, 트렌지스터의 안정성이 떨어지는 것으로 보고 되고 있다. 그러나 IGZO 물질의 경우 결정학적으로 비정질이며 상온 및 저온에서 대면적으로 제작이 가능하고, 높은 전자 이동도의 특성을 가지고 있는 장점 때문에 최근 차세대 산화물 트렌지스터로 각광받고 있다. IGZO TFT 소자의 경우 Ag, Au, In, Pt, Ti, ITO 등 다양한 전극 물질이 사용되고 있는데, 이들 중 active channel과 ohmic contact을 이루는 Al, Ti, Ag의 적용을 통해 향상된 성능을 얻을 수 있다. 하지만 이들 전극 재료는 TFT 소자 제작시 필수적인 열처리 공정에 노출되면서 active channel 과 전극 사이 계면에 문제점을 야기할 수 있다. 특히, Ti의 경우 산화가 잘되기 때문에 전극계면에 TiO2를 형성하여 contact resistance의 큰 영향을 미치는 것으로 보고 되고 있다. 본 연구에서는 ohmic 전극재료인 Ti 또는 Ti/Au를 적용하여 TFT 소자 제작 및 특성에 대한 평가를 진행했으며, 열처리에 따른 전극과 IGZO 계면 사이의 미세구조와 전기적인 특성간의 상관관계를 연구하였다. 이를 통해, 소자 제작 공정을 최적화하고 신뢰성 있는 소자 특성을 얻을 수 있었다.

• Transactions on Electrical and Electronic Materials
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• v.18 no.6
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• pp.334-337
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• 2017

In this paper, to develop the ceramics with high $d_{33}$ and high $Q_m$ for ultrasonic transducer applications, $0.10Pb(Ni_{1/3}Nb_{2/3})O_3-0.07Pb(Mn_{1/3}Nb_{2/3})O_3-0.83Pb(Zr_{0.5}Ti_{0.5})_{0.83}O_3$ (PNN-PMN-PZT) ceramics were sintered at $940^{\circ}C$ using $CuO-Li_2CO_3-Bi_2O_3$ (CLBO) as a sintering aid by a traditional solid-state technique. The influence of zinc oxide additive on the physical properties of the prepared ceramics were systematically investigated. The R-T (rhombohedral-tetragonal) phase coexistence was found in the ceramics without zinc oxide additive and with increasing amounts of ZnO additive, the specimens showed a tetragonal phase. The formation of a liquid phase between ZnO and $Bi_2O_3$ contributed significantly to the grain growth of specimens. For the 0.1 wt% ZnO ceramics, the optimal physical properties of $d_{33}=370pC/N$, ${\varepsilon}_r=1,344$, $k_p=0.621$, and $Q_m=1,523$ were obtained.