奈米鎳鐵點陣結構於陽極氧化鋁上之製作與特性研究

Fabrication and characteristic study of nano-sized NiFe arrays on nanoporous anodic aluminum oxides

謝銘鴻(Ming-Hung Hsieh)

指導教授 ： 林鴻明

大同大學/工程學院/材料工程學系所/碩士(2010年)

摘要

本研究採用NiFe靶以磁控濺鍍方式將薄膜在陽極氧化鋁(AAO)基板上垂直成長單層點陣薄膜，因AAO脆性高，使其與Si基板以碳膠黏合提昇量測之便利性。利用磁控濺鍍系統在AAO基板上成長垂直NiFe奈米點陣薄膜，藉由不同的AAO孔徑，及改變單層膜厚，使其旋轉試片座從水平至垂直，與靶材保持每10°鍍不同厚度，最後再對以上各種不同成長條件NiFe薄膜之成份與磁性質探討。
藉由製程參數調整，可得具奈米陣列結構薄膜並具優良的軟磁性及熱穩定性。磁性量測結果顯示，由於AAO基板孔洞特性，鍍膜靶材原子將先沉積於corner處，膜厚較小（約10 nm）時可得點狀陣列結構，量測之矯頑磁力(Hc)可達約220 Oe，隨膜厚上升至約75 nm以上，將形成連續膜結構，此時矯頑磁力會下降至100 Oe ﹔而其AAO之size effect也將影響奈米點陣列的晶粒大小，即當AAO interpore較大時在35 nm即形成連續薄膜。
然而，若理論膜厚相同，薄膜直接沉積在Si基板上，其磁性質展現出domain wall motion ﹔但若沉積在AAO基板上，磁性質變成spin-rotation of Stoner-Wohlfarth （S-W）model。
若鍍膜時膜厚約35 nm以下，傾斜試片座角度，使濺鍍之靶材原子以不同角度沉積至AAO基板，探討angular variation of coercivity，發現隨鍍膜角度(50°～80°）增加，矯頑磁力可達約250 Oe，隨膜厚增加及鍍膜角度減小。即矯頑磁力（coercivity）隨著膜厚（thickness）上升而下降，但磁區大小、晶粒大小隨膜厚上升而增加，且隨膜厚增加，使其磁性質由Stoner-Wohlfarth model趨向domain wall motion type。

關鍵字

鎳鐵 ； 磁控濺鍍 ； 陽極氧化鋁 ； 奈米點陣結構

並列摘要

NiFe nanodot films are deposited on anodic aluminum oxide (AAO) with different pore diameters by sputtering. The scanning electron microscope images show that the morphology of the as-deposited film with lower thickness of about 10 nm is nanodot structure. The as-deposited nanodot film with good soft magnetic properties and thermal stability can be obtained by controlling the sputtering parameters. The film with high in-plane coercivity ( Hc// ) of about 220 Oe could be obtained as the thickness is 10 nm, and decreased to 100 Oe as the thickness is 75 nm. The size effect of AAO templates would influence the morphology of stacked atoms. The rim of the pores, which act as obstacles to the stacked atoms, could prevent them from forming continuous films. The magnetization switching characteristics of the nanodot films are investigated experimentally and micromagnetically in more detail by measuring the angular dependence of the coercivity. This work showed that the effect on their magnetic properties associated with film thickness and morphology of NiFe nanodot films. The average size of magnetic domains and grains are increased with film thickness, leading to the decrease in in-plane coercivity. The magnetic properties strongly relate to the microstructure of NiFe films. The angular dependence of coercivity revealed that by increasing the film thickness, the magnetization reversal is changed from Stoner-Wohlfarth to domain-wall-motion.

並列關鍵字

Sputter ； NiFe ； AAO ； Nanodot structure

參考文獻

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