Co(3d) 및 Er(4f) 불순물을 첨가한 CdS 단결정의 광학적 특성

국문 초록 (Abstract)

목 적: Iodine을 수송매체로 사용한 화학수송법으로 성장시킨 CdS, CdS : Co2+ 및 CdS : Er3+단결정의 광학적 특성연구를 하였다.
방 법: CdS, CdS : Co 및 CdS : Er 단결정을 성장시키기 위하여 고순도(99.9999 %)의 cadmium, sulfur 를 mole비로 칭량하고 수송물질로 iodine(순도 99.99%)을 함께 준비된 석영관 안에 넣고, 석영관 내부의 진 공을 5×10-6torr로 유지하면서 봉입하여 성장용 ampoule을 만들었다. 단결정을 성장시키기 위하여 시료 출발 측을 900 ℃, 성장 측을 700 ℃로 하여 7일간 성장시켰다. 성장된 단결정에서 iodine 을 제거하기 위하여 출발 측의 전원을 차단하고 성장 측의 온도를 250℃에서 10 시간동안 유지하여 전원을 끊고 실온까지 서냉하여, CdS, CdS : Co 및 CdS : Er단결정을 성장시켰다. 성장된 단결정의 결정구조는 X-ray diffractometer를 사용하여 X선 회절선을 측정하였고, 광흡수 특성은 UV-VIS-NIR spectrophotometer 로 측정하였다.
결과 및 고찰: XRD로 측정한 X선 회절무늬 peak 해석으로부터 구한 CdS 및 CdS : Co2+(2mole%) 단결정의 결정구조는 defect chalcopyrite 구조이었으며 CdS : Er3+(2mole%) 단결정은 hexagonal 구조였다. 에너지 띠 간격은 직접 전이형 밴드구조를 나타냈다.
결 론: 성장된 CdS 및 CdS : Co2+(2mole%) 단결정의 결정구조는 defect chalcopyrite 구조이었으며, 격자 상수는 CdS 단결정의 경우 a = 4.139Å, c = 6.716Å이였고, 불순물로 cobalt를 첨가한 CdS : Co2+(2mole%) 단결정의 경우 a = 4.141Å, c = 6.720Å이였으며, 또한 erbium을 첨가한 CdS : Er3+(2mole%) 단결정의 구조 는 hexagonal 구조이었으며, 격자상수는 a = 4.135Å, b = 4.135Å, c = 6.706Å이었다. 298K에서 순수한 CdS 단결정의 에너지 띠 간격은 2.422e V이었고, 불순물로 전이금속인 cobalt(2mole%) 첨가할 때 에너지 띠 간격은 2.331e V, 또한 희토류금속인 erbium(2mole%) 첨가한 경우 에너지 띠 간격은 2.230e V 이었다.

다국어 초록 (Multilingual Abstract)

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 2.422e V , 2.331e V and 2.230 e V at 298K, respectively.

목차 (Table of Contents)

• Ⅰ. 서 론
• Ⅱ. 실 험
• 1. 단결정 성장
• 2. 성장된 단결정의 특성 측정
• Ⅲ. 실험결과 및 고찰
• 1. 단결정의 결정구조
• 2. 광학적 energy gap
• Ⅳ. 결 론
• 참 고 문 헌

참고문헌 (Reference)

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