• Journal of the Korean Vacuum Society
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• v.2 no.4
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• pp.486-490
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• 1993

Cd4SnSea6 & Cd4SnSe6 : Co2+ single crystals were grown by the chemical transport reaction (CTR) method. The grown single crystlas crrystallize in the monoclinic structrue and have the direct band gaps. The energy gaps of them are 1.68eV for Cd4SnSea6 & Cd4SnSe6 : Co2+ at 293K. The impurity opticla absorption peaks due to cobalt dped with impurity appear at 4879cm-1, 5392cm-1 and 6247 com-1, and are attributed to the electron transitions between the split energy levels of Co2+ ion sited at Td symmetry of Cd4SnSe6 single crystal.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.94-97
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• 2002

CdS and $CdS:Co^{2+}$ single crystals were grown by CTR method using iodine as transport material. The grown single crystals have defect chalcopyrite structure with direct band gap. The optical energy band gap was decreased according to add of Co-impurity. We can observed the Co-impurity optical absorption peaks assigned to the $Co^{2+}$ ion sited at the $T_d$ symmetry lattice and we consider that they were attributed to the electron transitions between energy levels of ions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.607-608
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• 2005

In this paper, author describe the undoped and $Co^{2+}$(0.5mole%) doped $Cd_4SnSe_6$ single crystals were grown by the chemical transport reaction(CTR) method. The grown single crystals crystallize in the monoclinic structure of space group Cc and have the direct band gap structure. The energy gaps of them are 1.68 eV for $Cd_4SnSe_6$ and 1.50 eV for $Cd_4SnSe_6:Co^{2+}$ at 300K respectively.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.16-21
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• 2001

Optical properties of $Ag_2CdSnSe_4$ and $Ag_2CdSnSe_4:Co^{+2}$ quaternary semiconductor single crystals grown by the chemical transport reaction method were investigated. The analysis of the X - ray powder diffraction measurements showed that these crystals have a wurtzite structure with lattice constants a = 4.357 $\AA$, c = 7.380 $\AA$, for $Ag_2CdSnSe_4$ and a = 4.885 $\AA$, c = 7.374 $\AA$, for $Ag_2CdSnSe_4:CO^{2+}$. The direct band gap at 298K, obtained from the optical absorption measurement, is found to be 1.21 eV for $Ag_2CdSnSe_4$ and 1.02 eV for $Ag_2CdSnSe_4:CO^{2+}$. The shrinkage of the band gap due to Co-doping is observed and is about 190 meV, We observed four absorption bands of $Co^{2+}$ ions in two near infrared regions of optical absorption spectra of $Ag_2CdSnSe_4$:$Co^{+2}$. These absorption bands were assigned as due to electronic transitions between the split energy levels of $Co^{2+}$ ions in $T_d$ crystal field under spin-orbit interactions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.539-545
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• 2001

Undoped and Co$^{2+}$ $\alpha$-Ga$_2$S$_3$ thin films were grown by spray pyrolysis method. It has been found that these thin films have a monoclinic structure and direct optical energy gap and indirect were located to 3.477eV and 3.123 eV at 10K respectively. In the photoluminescence due to a D0A(donor-acceptor) pair recombination were observed at 502 nm and 671 nm for the $\alpha$-Ga$_2$S$_3$ thin film, where is excited by the 325 nm-line of He-Cd laser. These peaks are identified to be corresponding to the electron transition between the energy levels of Co$^{2+}$ ion sited a the T$_{d}$ symmetry point in the $\alpha$-Ga$_2$S$_3$;Co$^{2+}$ thin film. film.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.52 no.2
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• pp.68-73
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• 2003

$Zn_4SnSe_6$ and $Zn_4SnSe_6:Co^{2+}$ single crystals were grown by the chemical transport reaction(CTR) method. They were crystallized in the monoclinic structure. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]. The direct energy gaps of $Zn_4SnSe_6$ and $Zn_4SnSe_6$:$Co^{2+}$ single crystals were given by 2.146[eV] and 2.042[eV] at 300[K]. The temperature dependence of the optical energy gap is well presented by the Varshni equation.

• Journal of Soil and Groundwater Environment
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• v.6 no.2
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• pp.15-22
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• 2001

Radiocarbon ($^{14}C$) and tritium in water have been applied to hydrogeology as a tool for dating of groundwater. The long half-life of $^{14}C$(5,730 years) makes it useful for evaluation of residence time of groundwater, However, the $^{14}C$ has not been applied to groundwater studies in Korea, owing to the absence of preparation line for $^{14}C$ analysis. By this time $^{14}C$ of groundwater has been analyzed mainly using benzene synthesizer, which is so complicate and time-consuming that has been is limitedly applied to hydrogeology. Recently, the direct $CO_2$ absorption method for $^{14}C$ analysis was developed and introduced to KAERI for the evaluation of domestic groundwater system. The results of $^{14}C$ in groundwater would be usefully applied to hydrogeological studies such as the well understanding of groundwater flow system in depth. The reliability of our $^{14}C$ data was confirmed by inter-comparison with the qualified international isotope laboratory.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1599-1602
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• 2002

$Zn_4SnSe_6$ and $Zn_4SnSe_6:Co^{2+}$ single crystals were by the chemical transport reaction method. They crystallized in the monoclinic structure. The direct energy band gaps of the $Zn_4SnSe_6$ and $Zn_4SnSe_6:Co^{2+}$ single crystals at 289K were found to be 2.146eV and 2.042eV. Optical absorption due to impurity in the $Zn_4SnSe_6:Co^{2+}$ single crystal was observed and described as originating from the electron transition between energy leveles of $Co^{2+}$ sited at $T_d$ symmetry point.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11b
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• pp.1-6
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• 2004

In this paper author describe the undoped and $Co^{2+}$ (0.5mole%)doped $Cd_4GeS_6$ single crystals were grown by the chemical transporting reaction(CTR) method using high purity(6N) Cd, $GeS_2$, S elements. It was found from the analysis of X-ray diffraction that the undoped and $Co^{2+}$(0.5mole%) doped $Cd_{4}GeS_{6}$ compounds have a monoclinic structure in space grop Cc. The optical energy band gap was direct band gap and temperature dependence of optical energy gap was fitted well to Varshni equation. Impurity optical absorption peaks due to the doped cobalt in the $Cd_4GeS_6:Co^{2+}$ single crystal were observed at 3593cm-1, 5048cm-1, 5901cm-1, 7322cm-1, 12834cm-1, 13250cm-1, 14250cm-1，and 14975cm-1 at 11.3K.

• Journal of the Korean Chemical Society
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• v.51 no.4
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• pp.331-338
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• 2007

A rapid, simple and sensitive spectrophotometric method was developed for the determination of cobalt(II) using 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) as a analytical reagent. The metal ion in aqueous medium forms a brown coloured complex with HMBATSC at pH 6.0. The complex has two absorption maxima at 375 nm and 390 nm. At 375 nm, the reagent shows considerable absorbance, while at 390 nm the reagent does not shows appreciable absorbance. Hence, analytical studies were carried out at 390 nm. Beer's law is obeyed in the range of 0.059-2.357 μg ml-1 of Co(II). The molar absorptivity and Sandall's sensitivity of the method are 2.74×104 l mol-1 cm-1 and 0.0024 μg cm-2 respectively. The interference of various diverse ions has been studied. The complex has 1:2 [Co(II)- HMBATSC] stoichiometry. A method for the determination of cobalt(II) by second order derivative spectrophotometry has also been proposed. The proposed methods were applied for the determination of cobalt(II) in alloy steels, vitamin B12 and in some biological samples.