• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.50-59
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• 1992

By means of X-ray photoelectron spectroscopy(XPS), the initial stages of the oxidation of the cleaved CdTe (110) surface and the sputtered CdTe surface with oxygen exposure are invetigated. From the analyses of the spectra of Te 3dsn, Cd 3d5/2, 0 ls and Cd MNN Auger lines, it is shown that two oxygen atoms bond to one Te atom at the initial stages.

• Journal of Powder Materials
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• v.7 no.1
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• pp.6-11
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• 2000

Two kinds of Bi2Te3 powders, pure Bi2Te3/2vol.%ZrO2, have been prepared by a mechanical grinding process process. Effect of mixing of the powders on thermoelectric of the sintered body has been investigated by measuring Seebeck Coeffcient, specific electric resistivity and thermal conductivity. With an increase in the weight fraction of the Bi2Te3/2vol.%ZrO2 powder from 0 to 40wt.%. Especially, the figure of merit of the mixedBi2Te3 sintered body increases and thereafter dedreases above 40wt.%. Especially. the figure of merit of the mixed Bi2Te3 sintered bodies with mixing of Bi2Te3/2vol.%ZrO2 powder increased about 1.3time in comparison with the value of the specimen before mixing. Mixing of two kinds of Bi2Te3 powders which have different theramal and electric propertries with each other seemed to be useful methob to increase the figure of merit of Bi2Te3 sintered body.

• Journal of the Korean Magnetics Society
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• v.21 no.4
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• pp.127-131
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• 2011

In this paper, we study the electronic and magnetic properties of Cr substituted SiTe in the rock-salt structure compound using the full potential linearized augmented plane wave method within the generalized gradient approximation to the exchange correlation potential. Two stoichiometries are studied: $CrSi_3Te_4$ with 25 %, and $CrSiTe_2$ with 50 % Cr substitution. We found, from the total energy calculations, that the equilibrium lattice constant for cubic $CrSi_3Te_4$ is 11.64 a.u. and a = 7.89 a.u. and c = 11.13 a.u. for tetragonal $CrSiTe_2$. The integer value of the calculated magnetic moment per unit cell, $4{\mu}_B$ for $CrSiTe_2$ suggests that this compound is halfmetallic. The magnetic moment per unit cell for $CrSi_3Te_4$ is slightly larger than $4{\mu}_B$. The magnetic moment on Cr atoms are 3.61 and $3.62{\mu}_B$ in the $CrSi_3Te_4$ and $CrSiTe_2$, respectively. The presence of Cr atoms causes that the other atoms become slightly magnetized in both compounds. The electronic properties and the magnetism are discussed with the calculated spin-polarized density of states.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2167-2170
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• 2013

A low-cost and simple recycling process of waste thermoelectric modules has been investigated using chemical reduction methods. The recycling is separated by two processes, such as dissolving and reduction. When the waste thermoelectric chips are immersed into a high concentration of $HNO_3$ aqueous solution at $100^{\circ}C$, oxide powders, e.g., $TeO_2$ and $Sb_2O_3$, are precipitated in the $Bi^{3+}$ and $HTeO{_2}^+$ ions contained solution. By employing a reduction process with the ions contained solutions, $Bi_2Te_3$ nanoparticles are successfully synthesized. Due to high reduction potential of $HTeO{_2}^+$ to Te, Te elements are initially formed and subsequently $Bi_2Te_3$ nanoparticles are formed. The average particle size of $Bi_2Te_3$ was calculated to be 25 nm with homogeneous size distribution. On the other hand, when the precipitated powders reduced by hydrazine, $Sb_2O_3$ and Te nanoparticles are synthesized because of higher reduction potentials of $TeO_2$ to Te. After the washing step, the $Sb_2O_3$ are clearly removed, results in Te nanoparticles.

• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.1-8
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• 2015

Thermoelectric (TE) technology is becoming increasingly important in applications of solid-state cooling and renewable energy sources. $Bi_2Te_3$-based TE materials are widely used in small-scale cooling and temperature control applications; however, higher levels of TE performance are required for new applications such as large-scale cooling (e.g., domestic refrigerators or air conditioners) and for highly efficient power generation system. Recently, the TE performance of $Bi_2Te_3$-based materials has been remarkably enhanced by the introduction of nanostructuring technologies which can be used to prepare TE raw materials. Because it takes into account the theoretical and experimental characteristics, nanostructuring has been shown to be one of the most promising ways to realize the simultaneous control of the electronic and thermal transport properties. In this review, emphasis is placed on bulk-type nanostructured $Bi_2Te_3$-based TE materials. Nanostructuring technologies for enhanced TE performance are summarized, and a few important strategies are presented.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.248-250
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• 1987

Transparent CdS films with low electrical restivity on glass substrates were prepared by coating a CdS slurry which contained 10 wt.% $CdCl_2$, and sintering in a nitrogen atmosphere at $600^{\circ}C$ for 2hr. All-polycrystalline CdS/CdTe solar cells were fabricated by coating CdTe slurries, which contained 1.0 or 4.5 wt.% $CdCl_2$, on the sintered CdS films and sintering at $700^{\circ}C$ for various periods of sintering. The spectral responses of the sintered CdS/CdTe solar cells were measured and compared with theoretically calculated quantum efficiency. The spectral responses of the sintered CdS/CdTe solar cells in the short-wavelength region decreases with-increasing sintering time. The poor response in this region is attributed to the existence of the Cd-S-Te solid solution in the compositional junction. The decrease in the maximum response in the long-wavelength region as the sintering exceeds certain time appears to be caused by the increase in the depth of the buried homo junction and by the increase in the series resistance. The $CdCl_2$ in the CdTe layer during sintering enchances the interdiffusion of S, Te or donor impurities across the metallurgical Junction causing the formation of deeper n-p junction in the CdTe layer.

• 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 Surface Science and Engineering
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• v.49 no.1
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• pp.40-45
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• 2016

Recently, $Bi_2Te_3$-based alloys are the best thermoelectric materials near to room temperature, so it has been researched to achieve increased figure of merit(ZT). Ternary compounds such as Bi-Te-Se and Bi-Sb-Te have higher thermoelectric property than binary compound Bi-Te and Sb-Te, respectively. Compared to DC plating method, pulsed electrodeposition is able to control parameters including average current density, and on/off pulse time etc. Thereby the morphology and properties of the films can be improved. In this study, we electrodeposited n-type ternary Cu-doped $Bi_2(Te-Se)_3$ thin film by modified pulse technique at room temperature. To further enhance thermoelectric properties of $Bi_2(Te-Se)_3$ thin film, we optimized Cu doping concentration in $Bi_2(Te-Se)_3$ thin film and correlated it to electrical and thermoelectric properties. Thus, the crystal, electrical, and thermoelectric properties of electrodeposited $Bi_2(Te-Se)_3$ thin film were characterized the XRD, SEM, EDS, Seebeck measurement, and Hall effect measurement, respectively. As a result, the thermoelectric properties of Cu-doped $Bi_2(Te-Se)_3$ thin films were observed that the Seebeck coefficient is $-101.2{\mu}V/K$ and the power factor is $1412.6{\mu}W/mK^2$ at 10 mg of Cu weight. The power factor of Cu-doped $Bi_2(Te-Se)_3$ thin film is 1.4 times higher than undoped $Bi_2(Te-Se)_3$ thin film.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.741-742
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• 2011

XRD 결과와 TEM 분석으로부터 열처리효과에 따른 Bi-Te 박막의 미세구조 변화를 확인하였다. $Bi_2Te_3$ 상이 $SiO_2$ 와 Bi-Te 박막의 경계면을 따라서 성장하였고 이는 열전성능에 중요한 영향을 미치는 것을 확인하였다.

• Journal of Surface Science and Engineering
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• v.42 no.5
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• pp.197-202
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• 2009

The electrodeposition in acidic aqueous electrolyte bath of cadmium telluride on gold electrodes has been studied by electrochemical analysis. Conventional cyclic voltammetry using potentiostat is considered as a reliable method to study electrochemical behavior of electrodeposition of CdTe. In this paper, the mechanism of CdTe deposition and its cyclic voltammetry were studied with the Te ion concentration, temperature, potential, and scan rate. We also investigated surface morphologies using FESEM and atomic composition of Cd and Te using EDS. Atomic composition of Cd and Te were varied with Te ion concentration in the electrolyte.