• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.515-517
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• 2003

In order to assess the risk of adverse health effects on human exposure to arsenic and heavy metals influenced by past mining activities, environmental geochemical surveys were undertaken in the abandoned metal mine areas (Dongil Au-Ag-Cu-Zn, Okdong Cu-Pb-Zn, Songcheon Au-Ag, Dongjung Au-Ag-Pb-Zn, Dokok Au-Ag-Cu and Hwacheon Au-Ag-Pb-Zn mines). Arsenic and other heavy metals were highly elevated in the tailings from the Dongil, the Songcheon and the Dongjung mines. High concentrations of heavy metals except As were also found in tailings from the Okdong, the Dokok and the Hwacheon mines. These significant concentrations can impact on soils and waters around the tailing dumps. Risk compounds deriving from mine sites either constitute a toxic risk or a carcinogenic risk. The hazard index (H.I.) of As in the Dongil, the Okdong, the Songcheon and the Hwacheon mine areas was higher value more than 1.0. In the Okdong and the Songcheon mine areas, H.I. value of Cd exceeded 1.0. These values of As and Cd were the highest in the Songcheon mine area. Therefore, toxic risks for As and Cd exist via exposure (ingestion) of contaminated soil, groundwater and rice grain in these mine areas. The cancer risk for As in stream or ground water used for drinking water from the Songcheon, the Dongil, the Okdong, the Dongjung and the Hwacheon mine areas was 3E-3, 8E-4, 7E-4, 2E-4 and 1E-4, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.84-91
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• 2002

The stochiometric composition of $AgGaS_2$/GaAs polycrystal source materials for the $AgGaS_2$/GaAs epilayer was prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns it was found that the polycrystal $AgGaS_2$/GaAs has tetragonal structure of which lattice constant an and Co were 5.756 $\AA$ and 10.305 $\AA$, respectively. $AgGaS_2$/GaAs epilayer was deposited on throughly etched GaAs(100) substrate from mixed crystal $AgGaS_2$/GaAs by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively. The crystallinity of the grown $AgGaS_2$/GaAs epilayer was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2$/GaAs epilayer at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by $\alpha=8.695{\times}10^{-4}$ eV/K, and $\beta=332K$. From the photocurrent spectra by illumination of polarized light of the $AgGaS_2$/GaAs epilayer, we have found that crystal field splitting ${\Delta}Cr$ was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.63-70
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• 1994

Single crystals of the superionic conductor ${\beta}-Ag_3SI$ were prepared by thermal treatmentr from the reactant mixture of AgI and $Ag_2S$. The growing single crystals were made to spherical shape of $200{mu}m$ in diameter. The detailed structures analyses revealed that $Ag^+$ in ${\beta}-Ag_3SI$ distribute on 12h site of 4-coordination inpreference to 3c site of 6-coordination. The effective one-particle potential (o.p.p.). of $Ag^+$ along [110] direction was evaluated from the probability density function(p.d.f.) Activation energy calculated from the o.p.p. curve has been found to be 0.012 eV for the diffusion of $Ag^+$ on (001) plane in the ${\beta}-Ag_3SI$ structure.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.5
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• pp.706-711
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• 1986

The AgGa1-xInxSe2 films are deposited by a flash evaporation method onto pyrex glass substrates at temperatures between 5\ulcorner and 360\ulcorner. The single crystalline films which have X-ray diffraction peak of only (112) plane are preared at substrate temperature above 360\ulcorner. The prepared AgGa 1-xInxSe2 films are high photosensitive. The temperature coefficients of energy gap are found to be (-1.2~-4.0)x10**4 eV/K and (-3.1~-5.2)x10**-4 eV/K, and that of peak energy of spectral photoresponse curve are found to be (-1.1 ~ -3.0)x10**-4 eV/K(50K~100K) and (-2.4~-5.1)x10**-4 eV/K(100K~300K).

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.10-12
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• 1999

Optical properties of $Zn_2AgGaSe_4$ and $Zn_2AgGaSe_4$:$Co^{2+}$ crystals are investigated in the visible and near-infrared regions at 298K. The direct band gap at 298K is 1.630eV for the $Zn_2AgGaSe_4$ and 1.567eV for the $Zn_2AgGaSe_4$:$Co^{2+}$ crystals, respectively. In the optical absorption and PAS spectrum of the $Zn_2AgGaSe_4$:$Co^{2+}$, we observed five impurity absorption peaks at $4220cm^{-1}$, $5952cm^{-1}$, $12422cm^{-1}$, $12987cm^{-1}$ and $14184cm^{-1}$. These impurity absorption peaks are attributed to the electronic transitions between the split energy levels of $Co^{2+}$ ions with Td symmetry of $Zn_2AgGaSe_4$ host lattice. The crystal field parameter Dq, the Racah parameter B and the spin-orbit coupling parameter $\lambda$ are given by $442cm^{-1}$, $425cm^{-1}$ and $440cm^{-1}$, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.461.1-461.1
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• 2014

본 연구진에서는 기존에 Ag2S 양자점을 흡광층으로 활용하여 양자점 감응형 태양전지(QDSC)를 제작, 그 성능과 특징을 분석하여 발표한 바 있다. 기존 연구에서 제작된 Ag2S QDSC는 11 mA/cm2의 비교적 높은 광전류와 260 mV의 비교적 낮은 전압으로 인해 1.2%의 광전환효율 성능을 나타내는 것으로 보고되었다. 추후 연구로 진행된 본 결과에서는, 기존에 Single absorber로 사용된 Ag2S의 한계를 보완하기 위해 CdS를 도입하여 co-sensitization을 활용하였다. CdS는 약 2.3 eV의 밴드갭 에너지를 갖는 물질로, 1.1 eV의 밴드갭을 갖는 Ag2S에 비해 흡광 영역은 좁지만 그만큼 전자-정공 재결합을 억제할 수 있는 장점을 가지고 있다. 또한, 전도층으로 사용한 n-type 물질인 ZnO 나노선과의 밴드구조가 매우 적합하게 조화되어, ZnO/CdS/Ag2S 순서로 이종구조를 접합시켰을 때 세 물질의 Conduction band level과 Valence band level이 순차적으로 연결되는 cascade-shaped 밴드구조를 이루게 된다. 빛을 받아 Ag2S와 CdS에서 생성된 전자는 이 cascade 모양의 conduction band를 따라 순차적으로 ZnO로 잘 전달되게 되어, 효율 향상에 큰 도움을 주었다. 이런 장점들로 인해, CdS-Ag2S co-sensitized QDSC는 Ag2S QDSC에 비해 2배나 향상된 효율인 2.4%를 기록하였으며, 이는 IPCE spectrum 측정 등으로 근거가 뒷받침되었다.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.527-533
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• 1990

The AgI systems containing various mol% of AgBr and CuI were synthesized. X-ray analyses revealed that all synthesized systems had face centered cubic structures. Using impedance analyzer, electrical conductivity measurements of these systems were carried out at temperatures from 20 to 200$^{\circ}C$. From this measurement, it was found that the activation energies of these systems were in the range 0.6∼0.7 eV and the system containing 5 mol% AgBr showed the highest conductivity and the smallest activity energy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.7
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• pp.510-514
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• 2013

In order to prevent heat loss that occurs through the glass, low-emissivity (Low-E) coating methods with good insulating properties and high transmittance were used. InGaZnO/Ag/InGaZnO (IGZO/Ag/IGZO) multilayer thin films have been deposited on XG glass substrate by RF magnetron sputtering. Depending on the different thickness of Ag in multilayer films, the structural and optical properties of Low-E multilayer films were analyzed. By XRD analysis results, the multilayer thin films were observed to be amorphous structure regardless of Ag thickness. According to the AFM results, surface morphology of the multilayer films was observed and compared. Using UV-VIS spectroscopy, low emissivity property has been observed clearly with the transmittance of higher than 85% at visible range and lower than 30% at IR range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.122-123
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• 2007

Single crystal $AgGaSe_2$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $AgGaSe_2$ source at $630^{\circ}C$. The temperature dependence of the energy band gap of the $AgGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T)=1.9501 eV - $(8.79{\times}10^{-4}\;eV/K)T^2$/(T+250 K). The crystal field and the spin-orbit splitting energies for the valence band of the $AgGaSe_2$ have been estimated to be 0.3132 eV and 0.3725 eV at 10 K, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $AgGaSe_2$. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-},\;B_{1^-},\;and\;C_{1^-}$exciton peaks for n=1.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.170-175
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• 2008

Screen printed carbon electrodes (SPEs) modified with co-immobilized osmium-based redox polymers can be used to apply multi-detecting biosensors. In this study, we report our initial studies of multi-detecting biosensor concepts using two osmium-based redox polymers for horseradish peroxidase-mediated reduction of ${H_2}{O_2}$ coupled to glucose oxidase-mediated oxidation of glucose. We target to synthesize two osmium redox polymers of potentials use, a chloride-containing redox polymer ($E^{O'}$ + 0.520 vs. Ag/AgCl) and a methoxy-containing redox polymer $E^{O'}$ + 0.150 vs. Ag/AgCl). The former show good catalytic electrical signals with horseradish peroxidase and the latter's redox polymer is to be an effective redox mediator of glucose oxidation by glucose oxidase.