博碩士論文 952202005 詳細資訊


姓名 管曉慧(Hsiao-Hui Kuan)  查詢紙本館藏   畢業系所 物理學系
論文名稱 銦-鈷複合奈米材料的電子傳輸與磁阻探討
(Electron transport and magnetoresistivity of In/Co nanoparticle composites)
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摘要(中) 本實驗室利用了熱蒸鍍低真空冷凝製程製作銦奈米顆粒。我們採用16nm的銦奈米顆粒與26nm的鈷奈米顆粒,依各種不同質量比例調配後均勻混合,壓合製作成(In)x(Co)100-x奈米複合樣品,其中x=100、50、30、20、10;藉由不同比例的鈷改變樣品中的內部磁場來影響電阻率隨外加磁場改變,造成磁阻效應。並且施予不同的壓力製作不同壓合密度的樣品,研究顆粒間距對電阻率的影響,藉此探討磁性奈米複合材料的電子傳輸機制。
我們量測樣品的電阻率、磁阻率與磁化率,發現銦與鈷製成的複合材料的電阻率趨向於非金屬性,電阻率會隨溫度的下降而增加,且在低溫時會快速增加,我們利用電子定域跳躍模型解釋此現象。磁阻率對外加磁場的行為偏向於ZMR模型,外加場由0T開始增加時,磁阻率會隨外加磁場增加而增加,且會達到某一極限,當外加磁場持續增加,磁阻率會轉而變小,最後會得到一負磁阻。我們利用磁場下能階分裂與自旋電子分布解釋磁阻率轉折的現象。
摘要(英) Indium nanoparticle was fabricated by thermal evaporation method .Sample purity and diameter were characterized by x-ray diffraction scheme. The analysis result show the pure 16 nm indium nanoparticle were obtained. No trace of impurity and oxidation was found. The result powder was mix with 28 nm cobalt with proper mass ratio, which defined as (In)X(Co)100-X(X=0,50,30,20,10).
Temperature profile of electric transport properties of all samples were study by DC resistivity system. The measured curves were analysis both by tunneling and Mott’s VHR theory. The fitting result show Mott’s three-dimensional variable range hopping could well describe all resistivity cures, which implies the electric transport were implies three dimensional isotropic.
The MR ratio of all samples at selective temperature was measured . Positive magnetoresistance (MR) at low applied magnetic fields to a negative MR at high fields were observed in our In/Co nanocomposites.This behavior is originated from Zeeman split of free electron level(ZMR).Two competitions mechanism is suggested .At first , the applied field described the electron levels into parallel and antiparallel the field, which caused lower hopping activation energy of high spin electrons. In the second, the applied field also reduce number of population of such electrons . So that , results positive to negative MR ratio transition.
關鍵字(中) ★ 奈米顆粒
★ 熱蒸鍍低真空冷凝製程法
★ 磁阻率
★ 塞曼效應
★ 電阻率
★ 複合奈米材料
★ X光繞射儀
★ 穿隧性磁阻
★ 量子局域效應
★ 熱擾動效應
★ 量子穿隧效應
★ 電子穿隧式模型
★ 庫倫阻塞效應
★ 勞倫茲函數式擬合
★ 聚合密度
★ 莫特三維電子跳躍模型
★ 巨磁阻
★ 常磁阻
★ 電子跳躍式模型
關鍵字(英) ★ Thermal Tvaporator
★ Nanoparticle
★ resistivity
★ magnetoresistance
★ Zeeman effect
★ Nanopolymer Composites
★ quantum confinement effect
★ thermal fluctuation
★ Quantum tunnelling effect
★ coulomb blockade effect
★ Giant magnetoresistance(GMR)
★ Lorentzian profile fitting
★ X-
論文目次 論文摘要 .......................Ⅰ
Abstract .......................Ⅱ
致謝............................Ⅲ
目錄............................Ⅳ
圖目............................Ⅵ
表目............................Ⅹ
第一章 序論
1-1 金屬奈米顆粒的紹 ...............................1
1-2 複合奈米材料的導電特性..........................5
1-3 實驗動機........................................7
第二章 樣品備製與實驗儀器簡介
2-1 銦奈米顆粒的製備方法-熱蒸鍍低真空冷凝製程.......8
2-2 X光繞射儀......................................10
2-3 粒徑分析 ......................................12
2-4 複合奈米樣品製作 ..............................16
2-5 電阻實驗儀器與量測 ............................23
第三章 電阻與磁阻機制
3-1 電子跳躍式與穿隧式傳導.........................26
3-2 磁阻的定義與種類 ..............................33
3-3 穿隧性磁阻TMR..................................38
3-4 塞曼效應(Zeeman effect)之磁阻ZMR..............39
第四章 電阻實驗分析與物理意義探討
4-1 電阻率隨溫度量測結果與分析.....................42
4-2 不同成分造成電阻率的變化.......................49
4-3 複合材料的超導現象.............................53
第五章 磁阻實驗結果與物理意義探討
5-1 磁阻率與溫度關係...............................55
5-2 磁阻率隨聚合密度的變...........................58
5-3 磁阻率與磁化強度的關...........................62
5-4 磁阻率與Zeeman效應 ............................66
5-5 熱擾動導致磁阻率異常現象.......................67
第六章 結論........................................70
參考文獻.............................................72
參考文獻 參考文獻資料:
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指導教授 李文献(Wen-Hsien Li) 審核日期 2008-6-23
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