• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권7호
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• pp.382-387
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• 2000

The $CdAl_2S_4 and CdAl_2S_4 : Co^{2+}$ single crystals were grown by the chemical transport reaction method using iodine as a transport agent. The $CdAl_2S_4 and CdAl_2S_4 : Co^{2+}$single crystals were crystallized into a defect chalcopyrite structure. The optical energy gap of the $CdAl_2S_4 and CdAl_2S_4 : Co^{2+}$ single crystals was found to be 3.377 eV and 2.924 eV, respectively, at 300 K. Blue emission with peaks in 456nm~466nm at 280K was observed in the $CdAl_2S_4$ single crystal. Optical absorption and emission peaks due to impurities in the $CdAl_2S_4 Co^{2+}$ single crystal were observed and described as originating from the electron transition between energy levels of the $Co^{2+} ion sited at the Td symmetry point.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집
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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.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권5호
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• pp.296-302
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• 1999

$CdIn_2S_4 and CdIn_2S_4 : Co^{2+}$ singlecrystals of thenormal spinel structure were grown by the C.T.R. method. The optical energy band structure of these compounds had a indirect band gap at the fundamental optical absorption band edge. The direct and the indirect energy gaps are found to be 2.325 and2.179eV for $Cdln_2S_4$ , and 2.303 and 2.169eV for $CdIn_2S_4 and CdIn_2S_4 : Co^{2+}$ at 5K, respectivly. The fundamental absorption band edge of these single crystals shift to a shorter wavelength region with decreasing temperature, and the temperature dependence of the optical energy gaps in these compounds satisfy Varshni equation. The Varshni constants$\alpha and \beta$ of the direct energy gap are given by $13.39{\times}10_{-4}eV/K$ and 509 K for $Cdln_2S_4$ and $29.73{\times}10_{-4} eV/K$ and 1398K for $CdIn_2S_4 and CdIn_2S_4 : Co^{2+}$. The Varshni constants ${\alpha}and {\beta}$ of the indirect energy gap are given by 9.68${\times}10^{-4}$ eV/K 308K for $Cdln_2S_4$ and $13.33{\times}10_{-4}eV/K$ and 440K for $CdIn_2S_4 : Co^{2+}$ respectivly. The impurity optical absorption peaks due to cobalt dopant are observed in $CdIn_2S_4 : Co^{2+}$ single crystal. These impurity optical absorption peaks can be attributed to the electronic transitions between the split energy levels of $Co_{2+}$ ions located at $T_d$ symmetry site of $Cdln_2S_4$ host lattece.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.31-36
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• 2002

In this work $Cd_{4}GeSe_{6}$ and $Cd_{4}GeSe_{6}:Co^{2+}$ single crystals were grown by the chemical transport reaction method and the structure of $Cd_{4}GeSe_{6}$ and $Cd_{4}GeSe_{6}:Co$ single crystals were monoclinic structure. The temperature dependence of optical energy gap was fitted well to Varshni equation. Also, the entropy, enthalpy and heat capacity were deduced from the temperature dependence of optical energy gap.

• 한국전기전자재료학회논문지
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• 제11권9호
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• pp.693-699
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• 1998

In this work $Cd_4GeS_6:Co^{2+}$(0.5mole%) single crystals were grown by the chemical transporting reactiov(CTR) method using high purity(6N) elements. The grown single crystals crystallized in a monoclinic structure(space group Cc). The direct optical energy gap of this single crystals was found to be 2.445eV at 300K and the temperature dependence of optical energy gap was fitted well to Varshni equation. But at temperatures lower than 70K an anomalous temperature dependence of the optical energy gap was obtained. This anomalous temperature dependence accored well with the anomalous temperature dependence of the unit cell volume. Also, the entropy, enthalpy and heat capacity were deduced from the temperature dependence of optical energy gaps.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.25-30
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• 2002

The ternary semiconducting compounds of the $A_{4}BX_{6}$(A=Cd, Zn, Hg; B=Si, Sn, Ge; X=S, Se, Te) type exhibit strong fluorescence and high photosensitivity in the visible and near infrared ranges, so these are supposed to be materials applicable to photoelectrical devices. These materials were synthesized and single crystals were first grown by Nitsche, who identified the crystal structure of the single crystals. In this paper. author describe the undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ single crystals were grown by the chemical transport reaction(CTR) method using iodine of $6mg/cm^{3}$ as a transport agent. For the crystal. growth, the temperature gradient of the CTR furnace was kep at $700^{\circ}C$ for the source aone and at $820^{\circ}C$ for the growth zone for 7-days. It was found from the analysis of x-ray diffraction that undoped and $Co^{2+}$-doped $Zn_{4}SnSe_{6}$ compounds have a monoclinic structure. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy gaps. These temperature dependence of the optical energy gap were closely investigated over the temperature range 10[K]~300[K]