臺灣博碩士論文加值系統

本研究藉由雙離子束濺鍍系統製備Ta（10 min，約9 nm）/ MnBi（20 min約50 nm）/ Si wafer系統與SiO2（10 min，約25 nm）/ MnBi（20 min，約50 nm）/ Si wafer系統之薄膜試片，試片製備完成後，使用快速熱退火爐（RTA）進行真空熱退火製程，熱退火時間共60分鐘。沉積Ta與SiO2薄膜於最上層作為覆蓋層，以防止在後續熱退火製程過程中Mn氧化與Bi擴散，研究對於Mn55Bi45合金薄膜在不同覆蓋層下其微結構與磁特性之討論。在微結構部分，藉由穿透式電子顯微鏡（TEM）觀察其晶粒大小分布情況與晶體結構。由晶粒度分布圖可得兩系統之晶粒度分布在23-63 nm之區間，平均晶粒度為34-38 nm。由環狀繞射圖形可得知兩系統之薄膜皆為多晶結構。由環狀繞射圖形比對JCPDS cards推測其對應之結晶面，在兩系統中由結果可推測其對應晶面有α-Mn、Bi、O-MnBi、錳氧化物與LTP-MnBi。LTP-MnBi晶格常數在兩系統由推測晶格面後計算得到分別為a = 4.194 Å，c = 6.278 Å（Ta/ MnBi/ Si wafer）與a = 4.217 Å，c = 5.905 Å（SiO2/ MnBi/ Si wafer），晶格常數的改變可能原因來自於LTP-MnBi生成之薄膜含量少與其他元素與化合物含量高可能造成晶格變形。在磁特性部分，藉由振動樣品磁力計（VSM）測量其M-H curve，兩個系統量測所得之M-H curve均無明顯之磁滯曲線，推測原因可能為α-Mn、Bi、O-MnBi與錳氧化物生成，造成LTP-MnBi比例降低，造成無法觀測到磁特性。比較不同的覆蓋層，由對應結晶面之結果發現，SiO2中的氧可能在熱退火製程期間擴散而造成錳的氧化進而形成較多的錳氧化物；相對於SiO2，Ta作為覆蓋層較為適當。可再藉由調整薄膜緻密度使Ta緻密化以及調整Ta的厚度，使Ta覆蓋層更發揮效用。另外，可藉由降低熱退火製程溫度來避免O-MnBi的生成與Mn、Bi分離。

The thin films of two systems, Ta（10 min, around 9 nm）/ MnBi（20 min, around 50 nm）/ Si wafer系統與SiO2（10 min, around 25 nm）/ MnBi（20 min, around 50 nm）/ Si wafer, were prepared by the ion beam assisted deposition system (IBAD). After preparing the samples, the vacuum thermal annealing process was performed by the rapid thermal annealing furnace (RTA), and total annealing time was 60 minutes. Ta and SiO2 films were deposited as capping layers to prevent Mn oxidation and Bi diffusion during the annealing process. Effects of capping layers on microstructural and magnetic properties of MnBi alloy thin films were investigated in this study. In the part of microstructure, the grain size distribution and crystal structure were observed by transmission electron microscope (TEM). The distributions of two systems were in the range of 23-63 nm, and the average sizes of the grains were 34-38 nm. It could be found that the films of both systems were polycrystalline from the diffraction pattern. From the diffraction pattern, the corresponding crystallographic planes were compared with JCPDS cards. In the two systems, corresponding crystallographic planes were estimated including α-Mn, Bi, O-MnBi, manganese oxide and LTP-MnBi. The lattice constants of LTP-MnBi of the two systems were calculated from the crystallographic planes to be a = 4.194 Å, c = 6.278 Å (Ta/ MnBi/ Si wafer) and a = 4.217 Å, c = 5.905 Å (SiO2/ MnBi/ Si wafer), the change in lattice constant might be caused by the low content of LTP-MnBi but and high in other elements and compounds of the thin film, then resulting in lattice deformation. In the magnetic properties, the M-H curve measured by vibrating sample magnetometer (VSM), and the hysteresis curve was not obvious. It might be caused by the formations of α-Mn, Bi, O-MnBi and manganese oxide. The LTP-MnBi ratio was lower, and the polycrystalline structure of LTP-MnBi might be the cause, too. Comparing the different capping layers, it was found that the oxygen contained in SiO2 might diffuse during the annealing process to form more manganese oxides. Ta was more suitable to be the capping layer than SiO2. The Ta layer could be adjusted density and thickness to make the Ta cap layer more effective. The formation of O-MnBi and the decomposition of Mn and Bi can be avoided by lowering the annealing temperature.

摘要 i
Abstract ii
目錄 iii
表目次 vi
圖目次 vii
第一章 緒論 1
1-1 前言 1
1-2 基礎理論介紹 2
1-2-1 磁性材料 2
1-2-2 磁化曲線與磁滯現象 7
1-2-3 磁異向性（Magnetic anisotropy） 9
1-3 文獻回顧 13
1-3-1 Preparation and magnetic properties of MnBi [15] 13
1-3-2 Effect of composition and heat treatment on MnBi magnetic materials [16] 14
1-3-3 Low-temperature phase c-axis oriented manganese bismuth thin film with high anisotropy grown from an alloy Mn55Bi45 target [17] 16
1-3-4 Effect of capping layer on formation and magnetic properties of MnBi thin films [18] 18
1-3-5 Effect of oxidation on perpendicular magnetic behavior of MnBi thin films [19] 20
1-3-6 Coercivity enhancement and magnetization process in Mn55Bi45 alloys with refined particle size [20] 22
1-4 實驗動機 24
第二章 實驗程序與方法 25
2-1 實驗設計 25
2-2 材料選用 27
2-3 樣品製備 29
2-3-1 基材前處理 29
2-3-2 試片製備及熱退火處理 31
2-4 雙離子束濺鍍系統（Ion Beam Assisted Deposition，IBAD） 33
2-4-1 雙離子束濺鍍系統配置 33
2-4-2 雙離子束濺鍍系統介紹 34
2-4-3 Kaufman離子源 36
2-4-4 End-Hall離子源 39
第三章 分析儀器原理及其介紹 41
3-1 穿透式電子顯微鏡（Transmission Electron Microscopy，TEM） [34][35] 41
3-2 振動樣品磁力計（Vibrating Sample Magnetometer） [39][40] 45
第四章 實驗結果與討論 48
4-1 Ta/ MnBi/ Si wafer系統之研究 48
4-1-1 晶粒度大小與分布 48
4-1-2 晶體結構分析 49
4-1-3 磁特性討論 51
4-2 SiO2/ MnBi/ Si wafer系統之研究 52
4-2-1 晶粒度大小與分布 52
4-2-2 晶體結構分析 53
4-2-3 磁特性討論 55
4-3 兩系統之比較整理 56
4-3-1 晶粒度大小與分布 56
4-3-2 晶體結構分析 56
4-3-3 磁特性討論 57
第五章 結論 58
參考文獻 59

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