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KMID : 1159320150170030187
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Korean Journal of Vision Science
2015 Volume.17 No. 3 p.187 ~ p.193
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Optical properties of impurity Co(3d) and Er(4f)-doped CdS single crystals
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Lee Young-Hwan
Youn Jae-Tae
Hyun Seung-Cheol
Park Kwang-Ho
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Abstract
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Purpose: We investigated the optical properties of CdS, CdS : Co2+, CdS : Er3+ single crystals grown by Chemical Transport Method using Iodine as a transporting material.
Methods: For growing CdS, CdS : Co2+, CdS : Er3+ single crystals, we weighed high purity (99.9999%) cadmium and sulfur according to the mole ratio and poured them into quartz ampoul with iodine(99.99%). Then, sealing them, we made the quartz ampoul for growing CdS, CdS : Co2+, CdS : Er3+ single crystals under 5×10-6torr vacuum state. We have grown CdS, CdS : Co2+, CdS : Er3+ single crystals for 7 days as 900 ℃ for starting side and 700 ℃ for growing side. To eliminate iodine from grown single crystals, we shut off the power of starting side and maintained 250 ℃ of growing side for 10 hours. After that, for obtaining CdS, CdS : Co2+, CdS : Er3+ single crystals, the grown single crystals were annealed to room temperature. The crystal structures of the grown single crystals were analyzed from the X-ray diffraction pattern determined by using X-ray diffractometer. The optical absorption properties were examined by utilizing UV-VIS-NIR spectrophotometer.
Results and Consideration: The crystal structures of the CdS, CdS : Co2+(2 mole%) single crystals analyzed from the peaks of the X-ray diffraction pattern were defect chalcopyrite structures and that of CdS : Er3+(2 mole%) single crystals was hexagonal structure. The energy band gap structures of these single crystals were direct transition types.
Conclusions: The lattice constants of the CdS, CdS : Co2+(2 mole%) single crystals with defect chalcopyrite structures were a = 4.139Å, c = 6.716Å and a = 4.141Å, c = 6.720Å, respectively. The lattice constants of the CdS : Er3+(2 mole%) single crystals with hexagonal structures were a = 4.135 Å, b = 4.135Å and c = 6.706Å. And The energy band gap of the CdS, CdS : Co2+(2 mole%) and CdS : Er3+(2 mole%) single crystals which have direct transion types were 2.422?�� , 2.331?�� and 2.230 eV ㅍ at 298K, respectively.
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KEYWORD
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Chemical Transport Method, X-ray diffractometer, UV-VIS-NIR spectrophotometer, defect chalcopyrite, hexagonal
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