The structures and magnetic characterization of ion-beam sputtered CoO/Co/SiO2 thin films

In this study, the anti-ferromagnetic layer (CoO) and the ferromagnetism layer (Co) was prepared for dual ion beam sputtering (DIBS) to discuss the influence of microstructural and magnetometry properties. Step1. sputtering (Co) layer on sio2 substrate by using Kaufman ion source, Step2. sputtering (CoO) layer on (Co) layer. The (CoO) and (Co) bilayers consisted of a h.c.p. structure (Co, a=2.5Å，c=3.9Å) and a (15% O2/Ar) f.c.c. (rock-salt) structure (CoO, a=4.3Å).The TEM cross section shown the (Co) layer about 60nm and the (CoO) layer about 55nm, the interface between (CoO) and (Co) bilayers was very neat not diffuse and mixed.The CoO/Co grain size about 10~40nm from bright field and dark field. Measurement CoO/Co bilayers at room temperature, the Hc about 252Oe, the Hex shifting was not obvious, the cause of the room temperature higher than anti-ferromagnetic layer (CoO) Neel temperature (291K), the anti-ferromagnetic layer was paramagnetism, the CoO/Co bilayers was no exchange coupling effect. The CoO/Co/SiO2 ion bombardment depth profiling time at 1, 7, 15 minutes, each layer composition percentage were different,there are variations in each layer interface,but on other area composition were uniformity, no diffuse and no mixed each other.本研究使用雙離子束濺鍍系統來製備反鐵磁層(CoO)與鐵磁層(Co)的雙層薄膜，以探討其薄膜結構與磁性質的影響。實驗內容為先利用雙離子束濺鍍系統之Kaufman 離子源將鐵磁層薄膜(Co)鍍在SiO2基板上，之後再利用End Hall離子源將反鐵磁層薄膜(CoO)鍍於其上，並探討經轟擊過後CoO/ Co雙層薄膜的結構及磁性質。 離子束濺鍍之氧化鈷/鈷雙層薄膜則是由 h.c.p.結構之鈷，晶格常數為a=2.5Å，c=3.9Å，及fcc岩鹽(rock-salt)結構之氧化鈷(15% O2/Ar)所組成，晶格常數為a=4.3Å。TEM微觀分析，由橫截面影像得知，Co的薄膜厚度大約為60nm，CoO的薄膜厚度大約為55nm，CoO及Co的界面相當平整，並無相互擴散及混和的情況發生。由明視野及暗視野可推算出CoO/ Co的晶粒尺寸介於10~40nm之間。CoO/Co雙層薄膜於室溫下量測，其Hc約於252Oe，而交換偏壓場(Hex)沒有明顯的偏移，這是因為室溫下溫度尚未低於反鐵磁層的尼爾溫度所致(CoO~291K)，故反鐵磁層CoO在室溫下為順磁結構，故雙層薄膜無交換耦合效應發生。 CoO/Co/SiO2離子濺擊縱深分佈，分別於離子濺擊時間於1、7、15分鐘，發生明顯的成份百分比的變化，其表示各個鍍層組成成分比例之不同，所以在層與層交界區域才會發生比例之變化，但在其他區域的組成比例並無明顯變化，由此可看出各個鍍層組成之成分均勻，並無成分滲透至其他鍍層。目錄 IV 圖目錄 VI 表目錄 XI 第一章緒論 1-1 前言 1 1-2 基礎理論 2 1-2-1 磁性物質簡介 2 1-3交換耦合機制 7 1-3-1 理論模型 9 1-4 磁異向性 14 1-5 應用 18 1-5-1磁阻式隨機記憶體 18 1-5-2巨磁電阻 20 1-5-3穿隧式電阻 22 1-5 文獻回顧 23 第二章實驗 26 2-1 實驗設計 26 2-2 材料選用 27 2-3 基板前處理 28 2-4 薄膜製備 29 2-5 雙離子束濺鍍系統(Ion Beam Assisted Deposition, IBAD) 31 第三章分析儀器原理與介紹 37 3-1 X光繞射儀( X-Ray Diffraction, XRD ) 37 3-2 穿透式電子顯微鏡( Transmission Electron Microscopy, TEM ) 41 3-3 震動樣品磁力計( Vibrating Sample Magnetometer, VSM ) 47 3-4 X射線光電子能譜儀 ( X-ray Photoelectron Spectroscope, XPS ) 49 第四章結果與討論 52 4-1 X光繞射儀(XRD)分析 52 4-2 穿透式電子顯微鏡(TEM)微結構分析 54 4-3 震動樣品磁力計(VSM)磁性量測 57 4-4 X光光電子能譜儀(XPS)成份分析 59 第五章結論 63 第六章參考文獻 6