NiFe電鍍膜結構及磁性之研究

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题名:	NiFe電鍍膜結構及磁性之研究
其它题名:	Structures and Magnetic Properties of Electroplated NiFe Films
作者:	孔令丞
贡献者:	王昌仁;張晃暐 Wang, Chang-Ren;Chang, Huang-Wei 應用物理學系
关键词:	NiFe;電鍍;磁性 NiFe;Electroplate;Magnetic properties
日期:	2018
上传时间:	2019-01-10T09:13:36Z (UTC)
摘要:	由於Ni80Fe20坡莫合金(permalloy)具有高的磁導率(μ)、小的矯頑磁力(Hc)、良好的異向性磁阻(AMR)特性，可被應用於磁場感測器元件、磁紀錄元件及磁通導體等領域而備受矚目。因電化學法有設備簡單及成本低等優點，而近年來受到商業上關注。因此本文以電化學法製備NiFe膜，並且透過調整添加劑及製程參數(鍍製時間及電流密度)，研究其對NiFe膜成分、結構、表面形貌與磁性之影響。實驗結果顯示適量添加糖精，可以降低NiFe膜之表面粗糙度，其由添加1 g/L時的15 nm降低至添加4 g/L的5 nm，並在添加至5 g/L時上升至22 nm。添加1-2 g/L時因其粗糙度下降，其矯頑磁力(Hc)自4.1 Oe下降至3.8 Oe，而添加量為3 g/L開始，曲線出現雙肩曲線(two-shoulder loop)，這是因為當糖精含量在3 g/L以上時，NiFe開始有兩相共存的情形，因此雖然擁有較低之粗糙度，但卻無比3.8 Oe更小之Hc。雙極距離效應之研究結果發現，增加極距可抑制B.C.C.相之產生，進而獲得NiFe單相F.C.C.結構，並呈現高度的(111)方位並在極距為12 cm時，其Hc達到最小為3.8 Oe。變化不同電流密度之實驗結果顯示，NiFe膜在高於0.25 A/dm2鍍製下皆呈現高度F.C.C.結構之(111)優選方位。在電流密度達到1 A/dm2時發生了劈裂的現象，從XRD圖可見NiFe(111)繞射峰往低角度偏移的現象，這可能是拉伸應力的累積所造成的。其矯頑磁力從電流密度為0.5 A/dm2時的3.78 Oe，上升至電流密度為1 A /dm2時的8.75 Oe。NiFe膜生長在哈氏片與Cu薄膜厚度為50、100 nm上時，擁有(200)方位取向之繞射峰，在Cu薄膜厚度上升至200 ~ 300 nm時，則具有高度的(111)優選方位。當底層Cu膜厚度上升時，Hc從底層厚度為50 nm時的10.4 Oe下降至底層厚度為200 nm時之Hc (3.78 Oe)。在本研究中也發現，溶液配方在未加Ni2CO3時，不同膜厚之NiFe膜皆屬於面心立方(F.C.C.) 結構，隨著厚度的提升，其Ni之含量也會隨之提升(60-80 %)，並在1.2 μm後Ni80Fe20膜之成分趨於穩定。且隨著NiFe膜之厚度的提高，Hc由1.2μm之3.85 Oe持續下降至8μm之0.23 Oe。但因表面粗糙度提升之故，厚度8-24 μm時其Hc由0.23 Oe微幅升至1.1 Oe。AMR測量結果揭示AMR Ratio由厚度2μm之0.6 %上升至8 μm之1.1 %，可能與粗糙度逐漸下降有關。但在NiFe厚度提升至24 μm時， AMR Ratio下降至0.9 %，這可能與粗糙的表面有關。 Permalloy, Ni80Fe20, with high permeability, small coercivity (Hc), large anisotropic magnetoresistance (AMR) has received much attention due to the applications in the field sensor, magnetic storage devices, and spintronic devices. The electrochemical technology having the advantages of simple equipment and low price has attracted become the focus commercial attention in recent years. Accordingly, NiFe films were prepared by electroplating method in this study, effect of the plating time, additives and current density on the composition, structure, surface morphology, and magnetic properties are studied. The experimental results show that the proper saccharin addition could reduce the surface roughness of NiFe films from 15 nm for 1 g/L to 5 nm for 4 g/L, and therefore, the decrease of the coercivity from 4.1 Oe to 3.8 Oe. Besides, the change of distance (d) between electrodes also could modify the phase constitution, and increasing d to 12 cm could suppress the formation of BCC phase and therefore reduce the coercivity. Furthermore, effect of current density (J) is also studied. For J = 0.25-0.50 A/dm2, the films exhibit FCC phase with high (111) texture and low coercivity of 3.8 Oe, but increasing J to 1.00 A/dm2 increases coercivity to 8.8 Oe, passably related to the accumulation of tensile stress, found by XRD. Finally, NiFe thickness (t) on the structure and magnetic properties are also investigated. As the thickness increases, the Ni content in the films increases from 60% to 80 %, and the composition of the Ni80Fe20 film becomes stable for thickness larger than 1.2 μm. With increasing the thickness of NiFe film, Hc is decreased from 3.8 Oe for t = 1.2 μm to 0.2 Oe for t = 8 μm. However, due to surface roughening, Hc is increased to 1.1 Oe for t = 8-24 μm. AMR Ratio increased from 0.6 % for t = 2 μm to 1.1 % for t = 8 μm. However, when the thickness of NiFe is increased to 24 μm, the AMR Ratio drops to 0.9 %. AMR ratio may be related to surface morphology.
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