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ABSTRACT 10

제1장 서론 12

제2장 이론 14

제1절 반도체에서의 광흡수 14

제2절 광발광 현상 22

제3절 자유 이온장에서 Er3+ 이온의 에너지 준위(이미지참조) 30

제3장 실험 36

제1절 ZnGa₂O₄ 및 ZnGa2O4:Er3+ 형광체의 결정 성장(이미지참조) 36

제2절 ZnGa₂O₄ 및 ZnGa2O4:Er3+ 형광체의 구조분석(이미지참조) 38

제3절 ZnGa₂O₄ 및 ZnGa2O4:Er3+ 형광체의 광흡수 측정(이미지참조) 40

제4절 ZnGa₂O₄ 및 ZnGa2O4:Er3+ 형광체의 광발광 측정(이미지참조) 40

제4장 실험결과 및 고찰 43

제1절 ZnGa₂O₄ 및 ZnGa2O4:Er3+ 형광체의 결정구조(이미지참조) 43

제2절 ZnGa₂O₄ 및 ZnGa2O4:Er3+ 형광체의 광흡수 특성(이미지참조) 47

제3절 ZnGa2O4:Er3+ 형광체의 광발광 특성(이미지참조) 53

제5장 결론 58

참고문헌 59

Table. 2-3-1. Microstate of f3 configuration.(이미지참조) 33

Table. 2-3-2. LS-term splitting by J-value. 34

Table. 4-1-1. X-ray diffraction data of ZnGa₂O₄ and ZnGa2O4:Er3+...(이미지참조) 46

Table. 4-2-1. Direct energy gaps of ZnGa₂O₄ and ZnGa₂O₄:Er3+...(이미지참조) 52

Table. 4-3-1. Emission peak energies of the Er3+ ion in ZnGa₂O₄:Er3+...(이미지참조) 56

Fig. 2-1-1. Direct band transition in semiconductors. 15

Fig. 2-1-2. Indirect band transition in semiconductors. 20

Fig. 2-2-1. (a) Transition model of fluorescence. 24

Fig. 2-2-2. Transition model of luminescence in semiconductors. 29

Fig. 2-3-1. The energy level diagram of a Er3+ free ion.(이미지참조) 35

Fig. 3-1-1. (a)muffle furnace for growing ZnGa₂O₄ and ZnGa₂O₄:Er3+...(이미지참조) 37

Fig. 3-4-1. Schematic diagram of photoluminescence measurement system. 41

Fig. 3-4-2. The spectral response of detectors and gratings used for... 42

Fig. 4-1-1. X-ray diffraction patterns of ZnGa₂O₄ and ZnGa₂O₄:Er3+...(이미지참조) 44

Fig. 4-1-2. Lattice constant a(Å) of ZnGa₂O₄ and ZnGa₂O₄:Er3+ phosphors.(이미지참조) 45

Fig. 4-2-1. Optical absorption spectra of ZnGa₂O₄ phosphor at 297 K. 48

Fig. 4-2-2. Optical absorption spectra of ZnGa₂O₄:Er3+ phosphor at 297 K.(이미지참조) 49

Fig. 4-2-3. Plot of (α·hν)n vs. the incident photon energy hν in ZnGa₂O₄...(이미지참조) 50

Fig. 4-2-4. Plot of (α·hν)n vs. the incident photon energy hν in...(이미지참조) 51

Fig. 4-3-1. Photoluminescence spectrum of ZnGa₂O₄:Er3+ phosphor in the...(이미지참조) 54

Fig. 4-3-2. Photoluminescence spectrum of ZnGa₂O₄:Er3+ phosphor in the...(이미지참조) 55

Fig. 4-3-2. Energy level splitting and transition energies of Er3+ ion in...(이미지참조) 57

초록보기

 In the present work, basic studies on optical properties of ZnGa₂O₄ and ZnGa₂O₄ : Er3+ phosphors were carried out. The composition and structure of ZnGa₂O₄ and ZnGa₂O₄ : Er3+ phosphors were analysed, and the properties of optical absorption, photoluminescence were measured, and the site symmetry of erbium was studied. Whereas, the photoluminescence peaks due to erbium substitution were assigned using the Td crystal field theory. In this work, the several properties of ZnGa₂O₄ and ZnGa₂O₄ : Er3+ phosphors are follows Stoichiometry of these compound semiconductors were determined using the energy dispersive x-ray analyser(EDX). The quantitative ratios of composition elements between the starting samples and the measured samples are reasonable values from the results of EDX with in the limit of detection error. The x-ray diffraction(XRD) analysis revealed that ZnGa₂O₄ and ZnGa₂O₄ : Er3+ phosphors have a cubic structure and the samples were a layered type with the c-axis perpendicular to the layers in the crystals. The lattice constant of these samples were a=8.3348 A˚ for ZnGa₂O₄, and a=8.3354 A˚ for ZnGa₂O₄ : Er3+ Phosphors.

The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy band gaps. The direct energy gaps of ZnGa₂O₄ and ZnGa₂O₄ : Er3+ are given by 3.057 eV and 3.037 eV at 297 K, respectively.

The photoluminescence spectra of ZnGa₂O₄ : Er3+ measured in the wavelength ranges of 600 nm~800 nm at 300 K are observed in the regions 660 nm~712 nm and five sharp emission peak due to Er3+ ion.

These PL peaks were attributed to the radiative transitions between the split electron energy levels of the Er3+ ions occupied at Td symmetry of the ZnGa₂O₄ phosphor host lattice.