• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2895-2900
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• 2014

We fabricated quantum dot-sensitized solar cells (QDSSCs) using cadmium sulfide (CdS) and cadmium telluride (CdTe) quantum dots (QDs) as sensitizers. A spin coated $TiO_2$ nanoparticle (NP) film on tin-doped indium oxide glass and sputtered Au on fluorine-doped tin oxide glass were used as photo-anode and counter electrode, respectively. CdS QDs were deposited onto the mesoporous $TiO_2$ layer by a successive ionic layer adsorption and reaction method. Pre-synthesized CdTe QDs were deposited onto a layer of CdS QDs using a direct adsorption technique. CdS/CdTe QDSSCs had high light harvesting ability compared with CdS or CdTe QDSSCs. QDSSCs incorporating single-walled carbon nanotubes (SWNTs), sprayed onto the substrate before deposition of the next layer or mixed with $TiO_2$ NPs, mostly exhibited enhanced photo cell efficiency compared with the pristine cell. In particular, a maximum rate increase of 24% was obtained with the solar cell containing a $TiO_2$ layer mixed with SWNTs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.74.1-74.1
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.300-301
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• 2002

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.73-76
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• 1997

A low loss x-cut LiNbO$_3$ optical waveguide was fabricated by Ti in-diffusion and the guided-mode properties and total insertion loss of pigtailing with polarization maintaining fiber(PMF) were investigated and measured at optical wavelength 15507. For formaing the waveguide, the parameters of diffusion Ti thickness, waveguide line-width, length, diffusion temperature, time and atmosphere were set 1400$\AA$, 8${\mu}{\textrm}{m}$, 3.3cm, 105$0^{\circ}C$, 8 hours and wet bubbled oxygen, respectively. and then After the polishing and pigtailing, it showed that total insertion loss was -4.1dB for TM mode, -5.5dB for TE mode, and mode size, that is, horizontal/vertical sizes were 13.87/18${\mu}{\textrm}{m}$ for TM mode, 9.61${\mu}{\textrm}{m}$/6.5${\mu}{\textrm}{m}$ for TE mode.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.247.1-247.1
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• 2016

Low-cost, high efficiency solar cells are tremendous interests for the realization of a renewable and clean energy source. ZnTe based solar cells have a possibility of high efficiency with formation of an intermediated energy band structure by impurity doping. In this work, ZnO/ZnTe:Cr and ZnO/i-ZnTe structures were fabricated by pulsed laser deposition (PLD) technique. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnTe target, whose density of laser energy was 10 J/cm2. The base pressure of the chamber was kept at approximately $4{\times}10-7Torr$. ZnTe:Cr and i-ZnTe thin films with thickness of 210 nm were grown on p-Si substrate, respectively, and then ZnO thin films with thickness of 150 nm were grown on ZnTe:Cr layer under oxygen partial pressure of 3 mTorr. Growth temperature of all the films was set to $250^{\circ}C$. For fabricating ZnO/i-ZnTe and ZnO/ZnTe:Cr solar cells, indium metal and Ti/Au grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. From the fabricated ZnO/ZnTe:Cr and ZnO/i-ZnTe solar cell, dark currents were measured by using Keithley 2600. Solar cell parameters were obtained under Air Mass 1.5 Global solar simulator with an irradiation intensity of 100 mW/cm2, and then the photoelectric conversion efficiency values of ZnO/ZnTe:Cr and ZnO/i-ZnTe solar cells were measured at 1.5 % and 0.3 %, respectively.

• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.263-269
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• 2011

In this study, the compositions for the microwave dielectric materials were investigated to obtain the improved dielectric properties, the high temperature stability, and the sintering temperature of less than $900^{\circ}C$, which was necessary for cofiring with the internal conductor of silver. In addition, the dielectric sheets were prepared by the tape casting technique, after which the sheets were laminated and sintered. In this process, the optimum ratio of powder and binder, laminating pressure, temperature, and possibility for cofiring with the internal conductor were studied. Finally, multilayer chip treplexer filter for the 800-2,000 MHz range were fabricated, and the frequency characteristics of the triplexer filter were investigated. When the $0.6TiTe_3O_8-0.4MgTiO_3+3wt%SnO+7wt%H_3BO_3$ ceramics were sintered at $820^{\circ}C$ for 0.3 hours, the microwave dielectric properties of the dielectric constant of 29.91, quality factor of 33,000 GHz, and temperature coefficient of resonant frequency of -2.76 ppm/$^{\circ}C$ were obtained. Using the Advanced Design System (ADS) and High Frequency Structure Simulator (HFSS), the multilayer chip triplexer filter acting at the range of 800-2,000 MHz were simulated and manufactured. The manufactured triplexer filter had the excellent frequency properties in the CDAM800, GPS and PCS frequency regions, respectively.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.430-436
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• 2006

Polarization-independent $Ti:LiNbO_3\;2{\times}2$ optical add/drop multiplexer for the 1550nm wavelength region is fabricated. The device consists of two input waveguides, two polarization beam splitters. two polarization conversion/electrooptic tuning waveguide sections, and two output waveguides. The single mode channel waveguides for both TE and TM polarizations are fabricated on a x-cut $Ti:LiNbO_3$substrate by Ti diffusion. Spectral section is based on phase-matched polarization conversion due to shear strain induced by a thick $SiO_2$ grating overlay film. An applied voltage tunes the device by changing the waveguide birefringence, hence the optical wavelength at which most efficient polarization conversion occurs. Tuning rate of 0.094nm/V with a maximum range of 17nm has been obtained. The nearest side-lobe is about 8.2dB. The FWHM is 3.72nm.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.69-79
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• 1999

In this paper, we proposed a diffuion model of Ti diffused lithium niobate optical waveguide for fabricating waveguides with high refractive index and compared with conventional one. The achivement of low optical insertion loss between waveguide interface and single mode fibers was discussed as a function of Ti thickness for $\lambda$=1.55$\mu\textrm{m}$ The proposed diffusion method exhibited higher refractive index waveguide than conventional one for $\lambda$=0.6328$\mu\textrm{m}$ We have achieved the total fiber-waveguide-fiber insertion loss as low as 0.5dB/cm in z-cut and 1$\pm$0.5dB/cm in x-cut for both TM and TE mode of Mach-Zehnder interferometric waveguide in the range of Ti thickness 1000-1400$\AA$ for $\lambda$=1.55$\mu\textrm{m}$ From these results, this diffusion model for making a low loss waveguide can be used for low-power-modulators and switches.

• Solar Energy
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• v.10 no.3
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• pp.53-59
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• 1990

[ $CdSe_xTe_{1-x}$ ] ($0{\le}x{\le}1$) thin films were deposited cathodically on Ti substrates in aqueous sulfric acid solution containing 1M $CdSO_4$ and 1mM$(TeO_2+SeO_2)$. The limiting current was observed in deposition potential ranging from -0.20 to -0.65 vs.Ag/AgCl ; although its value has changed a little depending on the mole ratio x, the limiting current was almost constant in deposition potential of -0.45V in spite of the change of mole ratio x. The crystal structure of the $CdSe_xTe_{1-x}$ thin films was cubic zinc-blonde in the range of mole ratio $x=0{\sim}0.8$, and hexagonal wurtzite in the mole ratio x=1 When the mole ratio changed from x=0 to x=0.8, diffraction peaks was shifted to the larger diffraction angle.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.385.1-385.1
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• 2014

$Bi_2Te_3$는 전기적, 열적 특성 등이 아주 흥미로운 소재로, 열전소자 응용 및 위상절연체(Topologycal insulator: TI)로써의 연구가 활발히 진행되고 있는 소재이다. 한편, 전기적, 광학적, 기계적, 열적 특성들이 매우 뛰어나 신소재로 각광받고 있는 그래핀은 나노소재의 합성 분야에서도 기판으로 활용되어, 최근에는 그래핀을 기판으로 한 고품질 나노소재의 합성에 관한 연구보고가 증가하고 있다. 이에, 본 연구에서는 그래핀을 $SiO_2$에 전사한 기판 및 $SiO_2$ 기판 위에 $Bi_2Te_3$ 나노 구조를 합성하고 다양한 분석을 하였다. 라만 스펙트럼 및 XRD를 통해 $Bi_2Te_3$ 임을 확인하였고, 비정질 $SiO_2$기판과 결정질 그래핀/$SiO_2$기판 그리고 구리호일과 그래핀/구리 호일 위에서 합성된 $Bi_2Te_3$ 나노구조를 SEM 및 TEM을 이용하여 비교 분석 하였다. 또한 기초적인 전기물성을 평가하였다.