臺灣博碩士論文加值系統

在本論文中，我們使用脈衝雷射沉積法在鈦酸鍶基板上製備氮化鈦薄膜，並在沉積過程中通入不同氧壓以製備不同形式的氧化鈦薄膜。藉由XRD、AFM、XAS的量測來觀察氧化過程中樣品的晶格結構、表面樣貌及電子結構，之後透過SQUID系統量測鐵磁性變化。結果顯示當氧壓大於1x10-4 torr出現鐵磁行為且隨著氧壓的增加鐵磁性行為逐漸變小而最終消失，我們推測鐵磁性來源為氧空缺所造成的。結合XRD、XAS及SQUID的結果，發現室溫鐵磁性與結構的改變有關，結構的改變及混亂將導致氧空缺的產生，使得束縛磁極化子(BMPs)之間的重疊性變高最後產生宏觀鐵磁性。

In this thesis, we have prepared oxidized titanium nitride thin films which were grown on STO(100) substrates by pulsed laser deposition (PLD). The surface morphology of samples with various oxygen pressure was studied by means of atomic force microscopy(AFM). The crystal structures and electronic states were investigated by means of x-ray diffraction(XRD) and x-ray absorption spectroscopy(XAS). The ferromagnetic measurements by means of superconducting quantum interference device(SQUID). The results of SQUID measurements showed room temperature ferromagnetism obviously when oxygen pressure greater than 1x10-4 torr and then disappeared gradually. The results of XRD, XAS and SQUID measurements indicated that the room temperature ferromagnetism changed with structures. The structures change and disorder led oxygen vacancies . Finally, the BMPs overlapped would produce ferromagnetism .

中文摘要 ----------------------------------------------------- I

英文摘要 ----------------------------------------------------- II

致謝 --------------------------------------------------------- III

目錄 --------------------------------------------------------- IV

第一章 緒論 -------------------------------------------------- 1

1-1 前言 ---------------------------------------------- 1

1-2-1 磁性材料與半導體 ------------------------------ 1
1-2-2 自旋電子元件的誕生 ---------------------------- 2

1-2-3 稀磁性半導體 ---------------------------------- 2

1-3 氧化物稀磁性半導體-二氧化鈦 --------------------- 4
1-4 動機 -------------------------------------------- 6
1-5 論文架構 ---------------------------------------- 7
第二章 樣品製備 ---------------------------------------------- 8

2-1 氮化鈦v.s基板的選擇 ----------------------------- 8

2-2 二氧化鈦晶格結構 -------------------------------- 9

2-3 脈衝雷射鍍膜(PLD)實驗步驟 ----------------------- 11 第三章 實驗儀器 ---------------------------------------------- 14
3-1 X光繞射儀 --------------------------------------- 14

3-2 原子力顯微鏡 ------------------------------------ 15

3-3 超導量子干涉儀 ---------------------------------- 16

3-4 X光吸收光譜 ------------------------------------- 17

第四章 實驗與結果 -------------------------------------------- 21
4-1 X光繞射儀測量結果 ------------------------------- 21

4-2 原子力顯微鏡測量結果 ---------------------------- 27

4-3 X光吸收光譜測量結果 ----------------------------- 30

4-3-1 XAS (O-K edge，TEY) --------------------------- 30

4-3-2 XAS (Ti-L3.2 edge，TEY) ----------------------- 34

4-3-3 XAS (N-K edge，FY) ---------------------------- 37

4-3-4 XAS (N-K edge，TEY) --------------------------- 40

4-4 超導量子干涉儀測量結果 -------------------------- 43

第五章 總結 -------------------------------------------------- 47
參考文獻 ----------------------------------------------------- 48

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