• Journal of Magnetics
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• v.15 no.2
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• pp.51-55
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• 2010

The electronic and magnetic properties of Cu-doped GaN with a Cu concentration of 6.25% and 12.5% are examined theoretically using the full-potential linear muffin-tin orbital method. The magnetic moment of Cu atoms decreases with increasing Cu concentration. The spin-polarization of Cu atoms is reduced due to the Cu d-d interaction depending on the distance between the nearest neighbouring Cu atoms. Cu atoms exhibits a clustering tendency in GaN. For Cu-adsorbed GaN thin films with a surface coverage of 0.25, the ferromagnetic state is found to be the energetically favourable state with an induced magnetic moment of $0.54\;{\mu}_B$ per supercell.

• Journal of Surface Science and Engineering
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• v.35 no.3
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• pp.127-132
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• 2002

High speed performance of ferroelectric Pb(Zr,Ti)$O_3$ (PZT) based capacitors is reported. La substitution up to 10% was performed to systematically lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a ($Ti_{0.9}$ /$Al_{0.1}$ )N/Pt conducting barrier composite. Ferroelectric capacitors substituted with 10% La show significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to a systematic decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. Furthermore, the samples doped with 10% La showed dramatically better retention and pulse width dependent polarization compared to the capacitors with 0% and 3% La. These capacitors show promise as storage elements in low power high density memory architectures.

• Journal of the Korean Ceramic Society
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• v.24 no.3
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• pp.270-276
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• 1987

The microstructure and dielectric properties of a SrTiO3-based GBL (Grain Boundary Layer) capacitor were investigated. The 0.6 mol% Nb2O5 doped SrTiO3 was sintered for 3 hr at 1450$^{\circ}C$ in mixed gas(N2/H2) atmosphere. The Nb2O5 promoted the grain growth of the SrTiO3 ceramics was decreased with the amount of Nb2O5. The oxide mixture(PbO, Bi2O3, B2O3) were painted on the reduced specimen and fired at 1000$^{\circ}C$ to 1100$^{\circ}C$ in air. The penetrated oxide mixture into specimen were located in grain boundaries. A SrTiO3-based GBL capacitor had the apparent permittivity of about 3.0${\times}$104, the dielectric loss of 0.01-0.02, and insulating resistance of 108-109$\Omega$.cm. The capacitor had the stable temperature coefficient of capacitance and exhibited dielectric dispersion over 107 Hz. The capacitance-voltage measurements indicated that the grain boundary was composed of the continuous insulating layers.

• Journal of Powder Materials
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• v.27 no.2
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• pp.154-163
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• 2020

Fluorescent nanoparticles are characterized by their unique properties such as luminescence, optical transparency, and sensitivity to various chemical environments. For example, semiconductor nanocrystals (quantum dots), which are nanophosphors doped with transition metal or rare earth ions, can be classified as fluorescent nanoparticles. Tuning their optical and physico-chemical properties can be carried out by considering and taking advantage of nanoscale effects. For instance, quantum confinement causes a much higher fluorescence with nanoparticles than with their bulk counterparts. Recently, various types of fluorescent nanoparticles have been synthesized to extend their applications to other fields. In this study, State-of-the-art fluorescent nanoparticles are reviewed with emphasis on their analytical and anti-counterfeiting applications and synthesis processes. Moreover, the fundamental principles behind the exceptional properties of fluorescent nanoparticles are discussed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.65-67
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• 2006

광통신이 발달하면서 보다 빠른 정보전송을 할 수 있지만 다른 전송매체와 마찬가지로 장거리 전송 시 손실이 발생하고 이러한 문제의 해결책으로 광 증폭기의 필요성이 대두 되었다. 기존의 광신호 증폭기에서는 광 신호를 전기신호 변환한 후 증폭하고 다시 증폭된 전기신호를 광신호로 변환하는 과정과 복잡한 구조는 전송시스템의 병목 문제를 유발하였다. 이러한 문제점을 해결할 수 있는 순수 광신호 증폭시스템인 어븀첨가광섬유증폭기 (EDFA)를 제작하고 EDFA의 이득평탄화를 위하여 이득평탄화 필터로 MLPFG를 제작하여 적용하였다. 제작된 EDFA는 20dB 이상의 신호 증폭을 보였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.727-730
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• 2002

Chalcogenide glassy semiconductors(CGS) can be obtained by the melt quenching technique. We have investigated the thin film heterostructures : metal-chalcogenide glassy semiconductors, where metal is copper, and chalcogenide glassy semiconductors are glasses of the system As-Se. Cu/CGS film heterostructure were produced in the vacuum evaporator by the method of vacuum thermal evaporation. Doped films are very sensitive to external actions, and this property allows developing supersensitive precision sensors of temperature, humidity, illumination, and etc. based on them. Cu/CGS film has shown that resistance strongly depend on the temperature. The slop of temperature and resistance shows linear.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.545-548
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• 2008

We report the synthesis of blue emitting materials with a new core structure containing indenopyrazine. Non-doped device using one of these materials as a blue emitter was found to exhibit high external quantumn efficiency of 4.6% and excellent color purity of (0.154, 0.078) as well as narrow emission band of 47nm FWHM.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.496-498
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• 2008

We have developed green phosphorescent organic light-emitting diodes (OLEDs) with high quantum efficiency. Wide-energy-gap material, 1,1-bis[(di-4-tolylamino) phenyl]cyclohexane (TAPC), with high triplet energy level was used as a hole transporting layer. Electrophosphorescent devices fabricated using TAPC as a hole-transporting layer and N,N'-dicarbazolyl-4,4'-biphenyl (CBP) doped with fac-tris(2-phenylpyridine) iridium [Ir(ppy)3] as the emitting layer showed the maximum external quantum efficiency ($\eta_{ext}$) of 19.8 %, which is much higher than the devices adopting 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (NPB) (${\eta}B_{ext}=14.6%$) as a hole transporting layer.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1445-1447
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• 2001

We have investigated about the grating formation of the $a-Se_{75}-Ge_{25}$ chalcogenide thin films. In this study, holographic gratings have been formed by using He-Ne laser(632.8nm) with different polarization states(linear, circular polarization). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. We have obtained maximum efficiency for Ag-doped thin film. It is observed the difference of the diffraction efficiency with polarization states. S:S-polarized state is shown high efficiency than the other polarization.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1462-1464
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• 1998

Poly-Si TFT(Thin Film Transistor) is a electronic device that can be applied to the field of large area electronics such as AMLCD. We have fabricated the poly-Si TFT with lateral body terminal that is counter-doped body electrode and investigated the electrical characteristics of it. The lateral body terminal being short with s terminal, we have measured the transfer charac (Vg-ld) and the output characteristic (Vd-ld) fabricated devices. The measured result showe only that leakage current in OFF-state was re and Kink effect in ON-state was suppressed bu that in output characteristic curve the output Id was sustained constantly with the output v Vd in the saturation region.