• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.32-37
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• 2002

Passive polarization mode splitters at λ= 1.55 ${\mu}{\textrm}{m}$ were designed and fabricated based on Ti:x-cut LiNbO$_3$ single-mode optical waveguide and two-mode interference theory. The splitting ratio with waveguide width 8 ${\mu}{\textrm}{m}$, branching angle 0.55$^{\circ}$ and interfering length 470 ${\mu}{\textrm}{m}$ showed 16.18 dB, 21.25 dB for TE and TM input polarization modes, respectively. Polarization cross-talk of -16.28 dB and -21.28 dB for TE and TM modes was achieved. Total insertion losses of 2.24 dB/cm (TE) and 2.41 dB/cm (TM) were also measured. The devices operated nearly wavelength independently over a range or 30 nm.

• 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.

• Journal of Sensor Science and Technology
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• v.10 no.1
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• pp.80-85
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• 2001

$Hg_{1-x}Cd_xTe$(MCT) thin films were grown onto ITO glass and titanium plate by stationary cathodic electrodeposition in aqueous solution contained $CdSO_4$, $TeO_2$, and $HgCl_2$. During deposition two main fabrication parameters were taken into account deposition potential and growth temperature. MCT films deposited by varying two parameters were studied by X-ray diffraction, electron probe micro analyser(EPMA) and scanning electron microscope measurements. It was shown by XRD and EPMA measurements that the structure of MCT films was zinc blonde and the composition of MCT films can be controlled with the deposition potential.

• Journal of Powder Materials
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• v.18 no.5
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• pp.437-442
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• 2011

The present study focused on the synthesis of Bi-Te-Se-based powder by an oxide-reduction process, and analysis of the thermoelectric properties of the synthesized powder. The phase structure, chemical composition, and morphology of the synthesized powder were analyzed by XRD, EPMA and SEM. The synthesized powder was sintered by spark plasma sintering. The thermoelectric properties of the sintered body were evaluated by measuring its Seebeck coefficient, electrical resistivity, and thermal conductivity. $Bi_2Te_{2.7}Se_{0.3}$ powder was synthesized from a mixture of $Bi_2O_3$, $TeO_2$, and $SeO_2$ powders by mechanical milling, calcination, and reduction. The sintered body of the synthesized powder exhibited n-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depend on the reduction temperature. The Seebeck coefficient and electrical resistivity of the sintered body were increased with increasing reduction temperature. The sintered body of the $Bi_2Te_{2.7}Se_{0.3}$ powder synthesized at $360^{\circ}C$ showed about 0.5 of the figure of merit (ZT) at room temperature.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.392-397
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• 2014

CuO nanotubes are synthesized using $TeO_2$ nanorod templates for application to $H_2S$ gas sensors. $TeO_2$ nanorod templates were synthesized by using the VS method through thermal evaporation. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction showed that the synthesized nanotubes were monoclinic-structured polycrystalline CuO with diameter and wall thickness of approximately 100~300 nm and 5~10 nm, respectively. The CuO nanotube sensor showed responses of 136~325% for the $H_2S$ concentration of 0.1~5 ppm at room temperature. These response values are approximately twice as high as that of the CuO nanowire sensor for the same concentrations of $H_2S$ gas. Along with the investigation of the performance of the sensors, the mechanisms of $H_2S$ gas sensing of the CuO nanotubes are also discussed in this study.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.355-359
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• 2013

In this paper, the $0.995(Li_{0.04}(Na_{0.56}K_{0.44})_{0.96}(Nb_{0.90}Ta_{0.10})_{0.998}Zn_{0.005}O_3+0.005KNbO_3+xwt%\;TeO_2$ lead-free piezoelectric ceramics for energy harvesting devices were fabricated by the conventional mixed oxide method. The microstructure, dielectric, and piezoelectric properties were investigated as a function of the $TeO_2$ addition. All the specimens showed an orthorhombic phase structure. At the composition ceramics doped with 0.1 wt%$TeO_2$, the optimum values of $d_{33}$= 212 pC/N, $d_{33}{\cdot}g_{33}=9.54pm^2/N$, and kp=0.448 were obtained, respectively. The results indicate that the composition ceramics is a promising candidate for energy harvesting devices applications.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.2
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• pp.29-35
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• 1993

A guided-wave TE to TM mode converter was demonstrated by using of the off-diagonal electrooptic coefficients in LiTaO$_{3}$. The input mode is coupled to the other orthogonal mode by the electrooptically induced off-diagonal polarizability. Compared with LiNbO$_{3}$, LiTaO$_{3}$ provides a smaller birefringence and thus a larger phase match period and larger optical bnadwidth. A novel electrode structure allowed a first-order Bragg-coupling phase matching. TE/TM mode conversion efficiency of 90% at 25 [V] was demonstrated with ${\lambda}$=0.63$\mu$m He-Ne laser.

• 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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• 2013.02a
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• pp.484-484
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• 2013

기존 진단용 Digital X-ray Detector이 직접방식에서는 a-Se (Amorphous Selenium)이 대중화되었지만 고전압을 인가하여야한다는 점과 그로 인한 물질 자체의 Life time 감소 등 여러 단점들 때문에 기타 후보물질들로 HgI2, PbI2, PbO, CdTe, CdZnTe가 연구 되고 있다. 이러한 후보 물질들 중 본 연구에서는 PVD (Physical Vapor Deposition)방식을 이용하여 Polycrystalline CdTe 박막을 제작하고 특성 향상을 위해 유전물질을 Passive layer와 Protect layer로써 증착하였다. 또한 유전체층의 위치에 따른 특성 분석을 위해 제작된 박막은 FE-SEM (Field Emission Scanning Electron Microscope), XRD (X-ray Diffraction)을 통해 구조적인 특성을 확인하였다. 그리고 입사되는 X-ray 선량에 의해 생성되는 전기적 특성을 분석하였다, 그 결과 박막의 Grain Size는 약 $5{\mu}M$이며 (111)방향의 주 peak를 띄는 Poly CdTe형태로 증착된 것을 확인하였다. 전기적인 신호 결과 Passive layer와 Protect layer를 증착한 박막 모두 Darkcurrent가 감소된 것을 확인하였다. 또한 Sensitivity 측정 결과 Passive layer를 삽입한 경우 신호 값이 감소하였으며 Protect layer를 삽입한 경우 신호 값의 변화가 일어나지 않았다. 그러므로 Protect layer를 등착한 박막의 경우 SNR이 현저히 높아지는 결과를 낳았다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.143-143
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• 2007

Bi-Te계 화합물은 상온영역($250^{\circ}C$이하)에서 열전특성이 우수하여, 냉각용 및 발전용 열전소자 재료로 사용되고 있다. 앞선 연구에서 MA법에 의한 La이 치환된 Bi-Te 진공가압 소결체의 열전특성이 $Bi_2Te_3$와 비교하여 향상된 값을 나타내었다. 본 연구에서는 Bi와 Te을 각각 0.01wt%, 0.02wt% La으로 미량 치환하여 melting법으로 제조한 분말을 $420^{\circ}C$, 200MPa로 가압 소결하였다. 가압 소결체의 열전특성은 Seebeck계수, 전기전도도. 열전도도를 측정하여 성능지수를 계산하였고 Bi-Te, (Bi-La)-Te, Bi-(Te-La)의 열전특성을 비교 분석하였다.