臺灣博碩士論文加值系統

本研究係以濺鍍(sputtering)方式製作NiO/Ni67Fe17Mo16雙層薄膜，藉由改變NiO、NiFeMo之膜厚，以了解膜厚與交換偏壓(exchange biasing field，He)及矯頑磁場(coercive field，Hc)間之關係。實驗結果顯示:交換偏壓及矯頑磁場隨NiO膜厚(≧30nm)之增加而減小；另一方面，交換偏壓也隨NiFeMo膜厚增加而減少。
本研究以AFM觀察NiO膜面，以探討其表面粗糙度對交換偏壓及矯頑磁場之影響。結果發現:隨著NiO膜厚的增加，由於表面柱狀結晶增大，晶粒數目減少，導致其平均表面粗糙度(mean surface roughness，Ra)降低。在交換偏壓方面，平均表面粗糙度增大將使得磁區變小而提升交換偏壓值；在矯頑磁場方面，粗糙度增大使得膜面上產生額外的磁耦合或磁雙極(dipole)之相互作用力，而使得矯頑磁場值上升。平均表面粗糙度為影響交換偏壓與矯頑磁場之重要因素。
由本研究得知，NiO50nm/NiFeMo10nm之雙層薄膜，其交換偏壓值為35.43 Oe，矯頑磁場值為4.02 Oe，其交換偏壓與矯頑磁場之比值(He/Hc)為8.81，此一比值適用於自旋閥磁阻之應用。

Bilayer films of NiO/Ni67Fe17Mo16 were fabricated by sputtering method. The effect of thickness of NiO and NiFeMo on the exchange biasing field (He) and coercive field (Hc) were studied. The results indicate that both the He and Hc decrease with increasing the thickness of NiO(≧30nm), and the He also decreases with increasing the thickness of NiFeMo.
Surface roughness of the NiO layer of the bilayer films was measured using an atomic force microscope(AFM). Mean surface roughness(Ra) was calculated to express the surface roughness. The value of Ra decreases with increasing the thickness of the NiO layer, due to an increase of the NiO columnar grain size but a decrease of its grain number. The increase of Ra on the oxide layer decreases the magnetic domain size, thus increasing the He. In the mean time, this increase in Ra induces additional magnetostatic coupling, or dipole interaction in the bilayer films, and results in an increase of Hc. Obviously, Ra plays an important role on the He and Hc of the NiO/NiFeMo bilayer films.
Through this investigation, a bilayer system of NiO50nm/ NiFeMo10nm films with optimum He and Hc was obtained. This system indicates the values of He at 35.43 Oe and Hc at 4.02 Oe, with a ratio of He/Hc at 8.81 It is very satisfactory for fabrication of a spin-valve magnetoresistance.

目錄
摘要…………………………………………………………………… Ⅰ
致謝…………………………………………………………………… Ⅱ
目錄…………………………………………………………………… Ⅲ
圖目錄………………………………………………………………… Ⅴ
壹.簡介………………………………………………………………… 1
貳.原理學說與文獻回顧……………………………………………… 3
一. 磁性物質之基本性質………………………………………… 3
二. 磁阻原理……………………………………………………. 5
三. 磁異向性與交換偏壓(He)及矯頑磁場(Hc)………………… 12
參.實驗方法………………………………………………………… 13
一. 實驗前準備………………………………………………… 13
1. 試片準備………………………………………………… 13
2. 濺鍍條件設定…………………………………………… 13
3. 膜厚校正………………………………………………… 14
二. 實驗流程……………………………………………………… 13
1.NiO/NiFeMo雙層薄膜製作………………………………… 14
2.NiO薄膜沈積速率……………………………………………15
3.自旋閥磁阻製作…………………………………………… 16
4.樣品分析…………………………………………………… 17
肆.使用儀器簡介………………………………………………………18
一. 實驗儀器……………………………………………………….18
二. 檢測儀器……………………………………………………… 18
1.磁光柯爾效應儀…………………………………………… 18
2.X-ray薄膜繞射儀………………………………………… 19
3.原子力電子顯微鏡………………………………………… 19
4.Auger能譜儀………………………………………………… 19
伍.結果……………………………………………………………… 20
一. NiO膜厚與交換偏壓He之關係……………………………….20
二. NiO膜厚與矯頑磁場Hc之關係……………………………… 21
三. NiFeMo膜厚與交換偏壓He之關係………………………… .22
四. He/Hc比值與NiO膜厚關係…………………………………..22
五. NiO膜表面粗糙度分析…………………………………….. 22
六. NiO/NiFeMo雙層薄膜之晶體結構分析……………………..23
七. Auger depth profile結果分析………………………….. 23
八. NiO薄膜沈積速率結果…………………………………….. 24
九. Spin-valve 結構之Moke 結果……………………………..24
陸.討論…………………………………………………………………26
一. NiO/Ni67Fe17Mo16的交換偏壓之探討…………………………..26
二. NiO/Ni67Fe17Mo16雙層薄膜中影響矯頑磁場之因素探討……. 31
三. He/Hc交換偏壓與矯頑磁場比值之評估……………………….34
四. 交換偏壓自旋閥多層膜之研究……………………………… 36
柒.結論…………………………………………………………………38
捌.未來展望……………………………………………………………39
玖.參考文獻……………………………………………………………40
圖目錄
圖 2-1 材料中電流受磁場影響改變路徑……………………………45
圖 2-2 磁阻效應中電場與磁場關係圖………………………………46
圖 2-3 (a) 電場與電流密度關係……………………………………46
(b) 磁阻薄膜膜面上之電流與磁化方向關係………………46
(c) 電場與電流在平行與垂直磁化方向之分量……………46
圖2-4 (a) 高磁場時，磁矩平行排列……………………………… 47
圖2-4 (b) 零磁場時，磁矩反平行排列…………………………… 47
圖2-5 自旋閥的典型結構…………………………………………… 48
圖2-6 自旋閥之磁滯曲線示意圖…………………………………… 48
圖2-7 NiO30nm/NiFeMo10nm之磁滯曲線…………………………… 49
圖2-8 簡化的交換偏壓作用模型…………………………………… 50
圖3-1 試片清洗流程圖……………………………………………… 51
圖3-2 實驗流程圖…………………………………………………… 52
圖5-1 NiO膜厚與交換偏壓關係圖………………………………….. 53
圖5-2 NiO膜厚與矯頑磁場關係圖………………………………….. 54
圖5-3 NiFeMo膜厚與交換偏壓關係圖……………………………… 55
圖5-4 NiO膜厚與He/Hc比值之關係圖……………………………… 56
圖5-5 NiO10nm薄膜之AFM量測結果…………………………………57
圖5-6 NiO30nm薄膜之AFM量測結果…………………………………58
圖5-7 NiO50nm薄膜之AFM量測結果…………………………………59
圖5-8 NiO70nm薄膜之AFM量測結果…………………………………60
圖5-9 NiO90nm薄膜之AFM量測結果 ……………………………… 61
圖5-10 NiO膜厚與平均表面粗糙度(Ra)關係圖…………………… 62
圖5-11 NiO(t)nm/NiFeMo10nm之XRD結果
其t=10、30、50、70、及90。…………………………… 63
圖5-12 NiO10nm/NiFeMo10nm之Auger depth profile結果………64
圖5-13 NiO30nm/NiFeMo10nm之Auger depth profile結果………65
圖5-14 NiO50nm/NiFeMo10nm之Auger depth profile結果………66
圖5-15 NiO70nm/NiFeMo10nm之Auger depth profile結果………67
圖5-16 NiO90nm/NiFeMo10nm之Auger depth profile結果………68
圖5-17 NiO50nm/NiFeMo10nm其NiO沈積速率與交換偏壓關係圖…69
圖5-18 NiO沈積速率為0.016 nms-1時，NiO50nm薄膜之AFM結果…70
圖5-19 NiO沈積速率為0.062 nms-1時，NiO50nm薄膜之AFM結果…71
圖5-20 NiO沈積速率為0.114 nms-1時，NiO50nm薄膜之AFM結果…72
圖5-21 NiO沈積速率為0.176 nms-1時，NiO50nm薄膜之AFM結果…73
圖 5-22 NiO沈積速率與平均表面粗糙度之關係圖………………… 74
圖 5-23 NiO50nm/NiFeMo10nm在不同NiO沈積速率下之XRD結果
(a) 沈積速率為0.016 nms-1…………………………………75
(b) 沈積速率為0.062 nms-1…………………………………75
(c) 沈積速率為0.176 nms-1…………………………………75
圖 5-24 NiO50nm/NiFeMo10nm/Cu(t)nm/NiFeMo10nm Spin Valve之磁滯曲線
。其中，t = 1、2、5、10、20、40、60及80。……76
圖 6-1 (a) NiO膜厚與其結晶性關係圖………………………………77
(b) NiO膜厚與NiO(200)/(111)比值之關係圖…………….77
圖 6-2 (a) NiO50nm/NiFeMo10nm 其NiO沈積速率與結晶性關係圖…78
(b) NiO50nm/NiFeMo10nm 其NiO沈積速率與
NiO(200)/NiO(111)比值之關係圖…………………… 78
圖 6-3 不同平均表面粗糙度之NiO/NiFeMo雙層薄膜示意圖………79
圖 6-4 平均表面粗糙度與交換偏壓關係圖………………………… 80
圖 6-5 平均表面粗糙度與矯頑磁場關係圖………………………… 81
圖 6-6 平均表面粗糙度與He/Hc比值之關係圖………………………82
圖 6-7 Sputtering 島狀成長示意圖…………………………………83
圖 6-8 (a) NiO/NiFeMo之狀態密度示意圖…………………………84
(b) NiO/NiFeMo/Cu/NiFeMo Spin-valve之狀態密度示意圖84

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