本論文研究摻雜不同離子的光觸媒材料 Cs2Nb4O11 粉末樣品、
不同厚度反鐵磁材料 BiFeO3 薄膜樣品成長在 YSZ(001) 基板、及反 鐵磁材料 YBaCuFeO5 單晶的光譜性質。實驗結果歸納為以下三點結 論：
第一，摻雜不同離子的 Cs2Nb4O11 之吸收能譜顯示，Ta 和S 離 子摻雜的比例提高，能隙值有明顯下降的現象。Cs2Nb4O11樣品之價 電帶及導電帶分別主要由 O 的 2p 及 Nb 的 4d 軌域所組成。Ta 離 子 取 代 Nb 離 子 及 S 離 子 取 代 O 離 子 ， 兩 者 皆 會 造 成 Cs2Nb4O11 的能帶結構改變，從第一原理理論計算的結果發現兩者皆 會使Cs2Nb4O11 的能隙減小，與實驗結果吻合。
第二， 10 nm 與 70 nm 厚四方晶系 BiFeO3 薄膜的室溫能隙值 分別約為 2.89 eV 及 2.87 eV。10 nm 與 70 nm 厚四方晶系 BiFeO3
薄膜的能隙值與溫度的變化關係，隨溫度的升高而下降，這是因為晶 格熱脹冷縮，電子與離子間交互作用變弱。10 nm 厚 BiFeO3 薄膜樣 品在高溫時(~ 670 K)，能隙值偏離玻色-愛因斯坦曲線，此溫度與其 它晶系的BiFeO3 薄膜尼爾溫度接近，但此現象在 70 nm 厚 BiFeO3
薄膜樣品不明顯，推測與複雜的自旋電荷間耦合現象有關。
第三， YBaCuFeO5 單晶的遠紅外光學電導率顯示 97、168、238、
656 cm-1 為 A2u 紅外活性振動模；121、188、275、330、574 cm-1 為
Eu 紅外活性振動模，藉由計算吸收峰強度較強的遠紅外聲子吸收峰
帄均頻率，得到其德拜溫度約為 375 K，此數值與非簡諧模型與波色 -愛因斯坦模型的擬合結果接近。室溫拉曼散射光譜顯示 347 cm-1 為 B1g 拉曼振動模；457、676 cm-1 為 A1g 拉曼振動模；192、280、576 cm-1 為 Eg 拉曼振動模。其中 676 cm-1 的 A1g 拉曼振動模呈現明顯 不對稱現象，代表聲子電子交互作用。隨著溫度下降，576 cm-1 Eg 振 動峰在第二尼爾溫度 (~ 175 K) 頻率位置偏離非簡諧模型理論預測 曲線，計算自旋聲子耦合係數約為 15.7 mRy/Å2，比較其他錳系過渡 金屬氧化物(數值接近)，顯示自旋間的關聯性與聲子有強烈耦合行為。
此外， YBaCuFeO5 單晶的能隙值在第一尼爾溫度附近 (~455 K)，
開始偏離波色-愛因斯坦模型理論預測曲線，推測與自旋電荷間耦合 現象有關。
未來，我們計劃量測四方晶系 BiFeO3 薄膜與 YBaCuFeO5 單晶 的低溫吸收光譜，了解 BiFeO3 薄膜之能隙與電子結構在低溫下的變 化。並了解 YBaCuFeO5 單晶之能隙與電子結構在溫度低於第二尼爾 溫度以下，是否也有自旋電荷耦合現象。也希望進行 YBaCuFeO5 單
晶的比熱實驗，得知德拜溫度，並與我們的光譜結果做一比較。
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