本實驗以熔鹽法及反應式濺鍍法兩種不同方式製備二氧化鈦並摻雜過渡金屬Co形成稀磁性半導體，對一維奈米結構及薄膜之實驗結果進行檢測與分析。
熔鹽法是將P25 TiO2粉末加入氯化鈉及磷酸氫二鈉中，後二者配製之成份以其共晶點為準，降低其形成溶融液之反應溫度，P25 TiO2中Anatase相參與反應並形成Na4TiP2O9，進而利用過飽和原理析出Rutile相TiO2，重新成核成長為TiO2奈米柱結構，摻雜的方式則同時在反應物中分別加入不同的鈷氧化物(Co3O4、CoO或Co(NO3)2)，得到的TiO2: Co之鐵磁性極弱，必須於真空環境600oC下進行退火以形成一維稀磁性半導體。後續的材料分析則以X光繞射儀(XRD)及拉曼光譜(Raman)鑑定二氧化鈦之晶相確為Rutile，電子顯微鏡(SEM)觀察二氧化鈦奈米柱形貌，X射線光電子能譜儀(XPS)鑑定Co鍵結為Co2+而非Co原子團，超導量子干涉儀(SQUID)測得真空退火後之樣品皆具有磁滯曲線，摻雜1 % Co(NO3)2之TiO2: Co粉末在室溫具有最高矯頑場，其值為238 ± 5 Oe，以此確認本實驗樣品為居禮溫度高於室溫之稀磁性半導體。
由於XRD及Raman分析皆發現熔鹽法易有其他雜相生成，為避免雜相對材料磁性的影響，並促進此材料實際應用之可能，另以反應式共焦磁控濺鍍法製備TiO2: Co薄膜，該系統以金屬Ti及Co為靶材，通入反應性氣體氧氣和氬氣其分壓分別為1x10-3 torr和 4x10-3 torr，基板溫度設定在400 oC及濺鍍功率為200 W，可得到較佳鍍率0.201Å/s，再改變不同Co摻量(濺鍍功率10 W- 40 W)，濺鍍之TiO2: Co薄膜其晶相為Anatase，必須置於大氣環境下之高溫爐持溫1000oC進行退火一小時，使其晶體結構完全轉變為Rutile相。實驗結果顯示藉由XRD及Raman分析確認TiO2: Co薄膜為Rutile相；SEM之試片剖面觀察得知薄膜厚度約為160 nm- 200 nm；XPS分析鑑定出Ti4+及O2-之鍵結並發現微弱的Co訊號；最後，以SQUID測得當濺鍍功率為20 W時，TiO2: Co薄膜具有63 ± 3 Oe之最高矯頑場，證明由反應式共焦磁控濺鍍法成功製備出室溫薄膜稀磁性半導體。
上述實驗結果顯示，熔鹽法及反應式濺鍍法皆可得到Rutile相之TiO2，藉由過渡金屬Co的摻雜及後續的退火製程，其磁性量測皆呈現磁滯曲線，驗證此兩種不同製程方法可分別獲得一維奈米結構及薄膜稀磁性半導體。

Room temperature ferromagnetism is the crucial property for the oxide material such as TiO2 to be successfully used in spintronic devices. In this study, we use two different methods, molten-salt method and reactive sputtering, to prepare Co-doped TiO2 as a dilute magnetic semiconductor (DMS) in the form of nanorods and thin films, respectively.
Molten-salt method had been used to grow TiO2 nanorods in a melted solution consisted of sodium chloride (NaCl) and sodium hydrogen phosphate (Na2HPO4) above the eutectic temperature of the mixture. P25 TiO2 powders containing both anatase and rutile phases were used as the TiO2 source in the reactants. During the heating process, the anatase phase reacted in the molten salt and the rutile phase consequently formed in the supersaturated solution. The rutile nano-particles in P25 powders acted as nucleation sites and grew along a preferred direction resulting in the formation of nanorods. Three Co compounds including Co3O4, CoO, and Co(NO3)2 were sequentially selected to be added in the reactant to test their effectiveness for doping. X-ray diffraction (XRD) and Raman analysis verified the rutile phase of as-grown TiO2 nanorods. The acicular nanorods were observed in scanning electron microscope (SEM). Bonding characteristics in the vacuum-annealed Co-doped TiO2 nanorods studied by X-ray photoelectron spectroscopy (XPS) indicated the oxidation state of cobalt in TiO2 was Co2+ rather than cobalt metallic clusters. Hysteresis curves of annealed samples were measured by using superconducting quantum interference device (SQUID). The highest coercivity of 238 ± 5 Oe was achieved from the sample doped with 1% Co(NO3)2 at room temperature.
Since some impurity phases, which may affect the magnetic properties, cannot be easily removed in the samples prepared by molten-salt method, we also used reactive magnetron co-sputtering to deposit TiO2: Co films. In this technique, Ti and Co metal targets were used as sputtering sources while an oxygen gas flow was introduced along with argon to promote the oxide formation. A proper deposition rate of 0.201Å/s was obtained for un-doped TiO2 films when they were grown with the RF power of 200 W in an Ar/O gas pressure ratio of 4 and the substrate temperature was kept at 400 oC. In addition, the RF power of Co target was varied from 10W to 40W to adjust the doping concentration of cobalt. The phases in as-grown films were identified to be anatase. In order to convert their structures completely into rutile, the films were annealed in air at 1000oC for one hour. XPS analysis of the doped TiO2 films indicated the presence of Ti4+, O2- and weak cobalt signal. SQUID measurements at room temperature showed that the Co-doped TiO2 film had the highest coercivity of 63 ± 3 Oe as the RF power of 20W was applied to the Co target.
In this work, our experiments showed that both techniques can realize the room-temperature ferromagnetism through the Co doping in rutile TiO2. It should be noted that post annealing in vacuum was crucial to enhance the magnetic properties in Co-doped TiO2 nanorods implying the dramatic effects of intrinsic point defects come from the oxide material.

總目錄
致謝 i
摘要 ii
Abstract iii
總目錄 v
圖目錄 vii
表目錄 ix
第一章 緒論 1
1-1前言 1
1-2理論及文獻 1
1-2-1二氧化鈦 1
1-2-1-1基本結構與特性 1
1-2-1-2常見一維奈米結構成長方式 3
1-2-2 以熔鹽法製備TiO2: Co一維奈米結構 5
1-2-3稀磁性半導體 7
1-2-3-1稀磁性半導體簡介 7
1-2-3-2稀磁性半導體的應用及挑戰 9
1-2-3-3二氧化鈦摻雜Co材料之文獻回顧 11
1-2-4反應式共焦磁控濺鍍法製備TiO2: Co稀磁性半導體 15
1-3研究動機及目的 19
第二章 實驗流程與分析儀器介紹 20
2-1實驗流程與步驟 20
2-1-1熔鹽法製備方式及步驟 20
2-1-2反應式共焦磁控濺鍍法製備方式及步驟 22
2-2分析方法與儀器介紹 24
2-2-1反射光譜儀(Reflectance spectroscopy) 24
2-2-2 X光繞射分析儀(X-Ray Diffraction, XRD) 24
2-2-3顯微拉曼光譜儀(Micro-Raman Spectroscopy) 25
2-2-4掃描式電子顯微鏡(Scanning Electron Microscope, SEM) 25
2-2-5 X射線光電子能譜儀(X-ray Photoelectron Spectroscopy, XPS) 25
2-2-6陰極光偵測系統(Cathodoluminescence System, CL) 26
2-2-7超導量子干涉儀(Superconducting Quantum Interference Device, SQUID) 27
第三章 實驗結果與討論 29
3-1以熔鹽法製備之TiO2: Co粉末性質分析 29
3-1-1結構分析 29
3-1-2陰極激發光譜儀分析 35
3-1-3鍵結分析 38
3-1-4室溫鐵磁性質分析 41
3-2以反應式濺鍍法製備之TiO2: Co薄膜性質分析 45
3-2-1不同製程參數對二氧化鈦薄膜厚度影響 45
3-2-1-1濺鍍功率對膜厚的影響 45
3-2-1-2溫度對膜厚的影響 45
3-2-1-3氧氣量(O2 / Ar+O2比)對膜厚的影響 46
3-2-2-1結構分析 47
3-2-2-2鍵結分析 49
3-2-3 TiO2: Co薄膜性質分析 51
3-2-3-1結構分析 51
3-2-3-2鍵結分析 55
3-2-3-3室溫鐵磁性質分析 56
3-2-3-3-1不同濺鍍功率之TiO2: Co薄膜 56
3-2-3-3-2不同薄膜厚度之TiO2: Co薄膜 58
第四章 結論 60
第五章 參考文獻 62

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