서지주요정보
코발트가 첨가된 첨정석 결정의 결정장과 광학적 특성에 관한 연구 = Crystal field and optical properties of cobalt doped spinel crystals
서명 / 저자 코발트가 첨가된 첨정석 결정의 결정장과 광학적 특성에 관한 연구 = Crystal field and optical properties of cobalt doped spinel crystals / 이석주.
저자명 이석주 ; Lee, Seok-Joo
발행사항 [대전 : 한국과학기술원, 2003].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8014240

소장위치/청구기호

학술문화관(문화관) 보존서고

DPH 03006

SMS전송

도서상태

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반납예정일

초록정보

In this thesis, the optical absorption spectra of cobalt doped $MgIn_2S_4$, $CdIn_2S_4$, $HgIn_2S_4$, $AgIn_5S_8$, $CuIn_5S_8$ and β-$In_2S_3$ spinel crystals measured at 7 K were studied. The photoluminescence (PL) spectra of $MgIn_2S_4$ single crystals were also investigated as a function of temperature and excitation laser intensity. Single crystals were grown by a chemical transport reaction method using iodine as a transporting medium. The PL band of $MgIn_2S_4$ was observed to be centered at 1.62 eV at 10 K and an excitation intensity of $0.02 Wcm$^{-2}$. The PL intensity decreased with increasing temperature and a rapid thermal quenching of the PL band was observed above 130 K. The red-shift of this band with increasing temperature was also observed. To explain the observed PL behavior, we propose that the emission is due to radiative recombination of a donor-acceptor pair, with an electron occupying a donor level located at 0.05 eV below the conduction band, and a hole occupying an acceptor level located at 0.62 eV above the valence band. Therefore, the blue-shift of the PL band with increasing excitation laser intensity is explained using the inhomogeneously spaced donor-acceptor pair model. The optical absorption spectra of cobalt doped $MgIn_2S_4$, $CdIn_2S_4$, $HgIn_2S_4$, $AgIn_5S_8$, $CuIn_5S_8$ and β -$In_2S_3$ spinel crystals measured at 7 K showed several peaks due to the $Co^{2+}$ impurities which were well explained in terms of the $T_d$ crystal field followed by the second order spin-orbit coupling. For $CdIn_2S_4$:Co$^{2+}$, the additional fine structure caused by the small trigonal ($C_{3v}$) distortion at Cd sites and the vibrating replicas was observed in the $^{4}A_2(^{4}F)→$^{4}T_1(^{4}F)$ transition. We could not observe any absorption peaks of cobalt ions with octahedral symmetry for all these crystals. But because the absorption of cobalt ions in the octahedral symmetry could be too weak to be observed, the possibility of cobalt ions being present in the octahedral sites cannot be excluded. The crystal field parameter Dq, the Racah parameter B, and the spin-orbit parameter λ obtained from the observed spectra show that the delocalization of the d electrons of $Co^{2+}$ ions is influenced by the Co-S bond length and the electronegativity difference between the metal (Me) and sulfur atoms of the host crystal. For cobalt doped spinel crystals, the $d$ electron delocalization increases in the order of $MgIn_2S_4$, $CdIn_2S_4$, $HgIn_2S_4$, $AgIn_5S_8$, $CuIn_5S_8$ and β -$In_2S_3$, and $CuIn_5S_8$. From this order, it can be concluded that the d electron delocalization increases with decreasing the Co-S bond length and the electronegativity difference of Me-S bond. The large $d$ electron delocalization in the β-$In_2S_3:Co^{2+}$ crystal means that vacancies at tetrahedral sites also increase the d electron delocalization.

서지기타정보

서지기타정보
청구기호 {DPH 03006
형태사항 v, 95 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Seok-Joo Lee
지도교수의 한글표기 : 김재은
지도교수의 영문표기 : Jae-Eun Kim
학위논문 학위논문(박사) - 한국과학기술원 : 물리학과,
서지주기 참고문헌 : p. 92-95
주제 첨정석
코발트
결정장
광발광
광흡수
spinel
cobalt
crystal field
photoluminescence
optical absorption
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