以錳摻雜單層二維結構硒化鎘半導體之合成、鑑定及應用

Abstract

本論文有兩個研究方向。第一個主題為探討不同濃度錳摻雜之單層二維硒化鎘奈米片，層與層之間利用乙二胺作為有機配位基，化學實驗式為MnxCd1-xSe(en)0.5。半導體之合成方法採用過去本實驗室發展的溶劑熱條件，以硼氫化鈉還原硒粉來取代價格昂貴的硒脲，做為硒的前驅物，並與欲摻雜金屬離子前驅物合成出MnxCd1-xSe(en)0.5 (x=0.5-7.7 %) 之單層二維膠體奈米片。透過場發射掃描穿透式球差修正電子顯微鏡、感應耦合電漿質譜分析儀、紫外光-可見光光譜儀、螢光光譜儀、磷光生命週期光譜儀、X光粉末繞射儀、X光吸收光譜延伸區精細結構、電子順磁共振光譜儀、磁圓偏振二色性光譜等儀器，鑑定錳摻雜後奈米片所產生的結構變化、磷光性質、電子順磁共振及磁光效應，並做進一步的探討及在稀磁性半導體之應用價值。 本研究的第二個主題探討錳摻雜二維奈米片MnxCd1-xSe(en)0.5，經由雷射誘發所產生之放光現象。以低於能隙 (2.85 eV) 之雷射光源，可經由雙光子吸收來激發單層二維奈米片的不同放光，並利用時間相關單光子計數系統及磷光光譜儀，比較以氙燈光源所產生之不同電子躍遷路徑，並以其放光強度及生命週期做為區分。此材料不僅可被低於能隙能量之雷射所激發，其放光機制亦驗證單層二維奈米片在光子上轉換、及二維量子發光體中的反聚束效應之可能性。There are two research topics in this thesis. The first one is to investigate properties of single-layer 2D CdSe nanosheets doped with Mn2+. Ethylenediamine (en) is used as a organic ligand bridging 2D layers with empirical formula of MnxCd1-xSe(en)0.5. Expensive Se precursor was replaced by a modified recipe containing Se and NaBH4 to synthesize 2D MnxCd1-xSe(en)0.5 (x=0.5-7.7 %) of various dopant concentarations via a solvothermal process. The structural changes, phosphorescence, paramagnetic resonance, and magneto-optical effects were characterized by TEM, ICP-MS, UV-vis, PL/PLE, PXRD, EXAFS, EPR and MCD spectroscopies in these doped 2D nanosheets sutiable for DMS applications. The second topic is to investigate PL phenomenon of MnxCd1-xSe(en)0.5 excited by Xe lamp and laser. For a laser of energy even below the energy gap (2.85 eV), two-photon absorption can be observed in these 2D nanosheets. The TCSPC and phosphorescence spectrometer are rationally used to compare electronic transitions via Xe lamp and laser exciation pathways. Photon upconversion and correclated anti-bunching effect are observed by the low-energy laser exciation, suggestive of future applications in 2D quantum emitters and beyond.