• 대한화학회지
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• 제40권5호
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• pp.295-301
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• 1996

$CaGa_1-xFexO_3-y$계의 x=0.25, 0.50, 0.75 및 1.00에 해당하는 고용체를 $1150^{\circ}C$, 대기압하에서 제조하였다. X-선 회절분석, Mohr염 정정, Mossbauer 분광분석을 수행하여 합성된 고용체들의 구조, 비화학량론적 화학식 및 양이온들의 분포를 결정한 후 전기전도도와 자기측정을 수행하여 물성에 관한 논의를 하였다. X-선 회절분석으로부터 얻은 모든 조성의 결정계는 브라운밀러릿 사방정계이다. 환산 격자부피는 단위세포의 차원이 다른 X=0.25의 조성을 제외하고 x값이 증가함에 따라 직선성을 가지고 증가한다. Mohr염분석 결과 고용체들은 $Fe^{4+}$ 이온을 포함하지 않고 산소공위의 몰수인 y값은 0.50으로 고정된 값을 가진다. Mossbauer 분광분석으로부터 Fe 이온의 산화상태, 배위상태, 브라운밀러릿 구조 및 $Ga^{3+}$와 $Fe^{3+}$ 이온의 분포를 논의하였다. 전기전도도와 활성화에너지는 x값이 증가함에 따라 각각 증가와 감소하고 이들로부터 전자 전기전도 메커니즘을 제안한다. x=0.50~1.00의 조성을 냉각하면서 자기측정을 수행할 때 열적 자기 히스테리시스가 나타나며 이러한 현상을 공간군과 Dzyaloshinsky-Moriya 상호작용을 기초로 논의하였다.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.263-272
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• 2011

Highly luminescent and monodisperse InP quantum dots (QDs) were prepared by a non-organometallic approach in a non-coordinating solvent. Fatty acids with well-defined chain lengths as the ligand, a non coordinating solvent, and a thorough degassing process are all important factors for the formation of high quality InP QDs. By varying the molar concentration of indium to ligand, QDs of different size were prepared and their absorption and emission behaviors studied. By spin-coating a colloidal solution of InP QD onto a silicon wafer, InP QD thin films were obtained. The thickness of the thin films cured at 60 and $200^{\circ}C$ were nearly identical (approximately 860 nm), whereas at $300^{\circ}C$, the thickness of the thin film was found to be 760 nm. Different contrast regions (A, B, C) were observed in the TEM images, which were found to be unreacted precursors, InP QDs, and indium-rich phases, respectively, through EDX analysis. The optical properties of the thin films were measured at three different curing temperatures (60, 200, $300^{\circ}C$), which showed a blue shift with an increase in temperature. It was proposed that this blue shift may be due to a decrease in the core diameter of the InP QD by oxidation, as confirmed by the XPS studies. Oxidation also passivates the QD surface by reducing the amount of P dangling bonds, thereby increasing luminescence intensity. The dielectric properties of the thin films were also investigated by capacitance-voltage (C-V) measurements in a metal-insulator-semiconductor (MIS) device. At 60 and $300^{\circ}C$, negative flat band shifts (${\Delta}V_{fb}$) were observed, which were explained by the presence of P dangling bonds on the InP QD surface. At $300^{\circ}C$, clockwise hysteresis was observed due to trapping and detrapping of positive charges on the thin film, which was explained by proposing the existence of deep energy levels due to the indium-rich phases.