L11 CoPt薄膜在玻璃基板上之磁性質及微結構研究

Magnetic properties and microstructure of CoPt L11 thin film on glass substrate

黃聖華(Sheng-Hua Huang)

指導教授 ： 孫安正

元智大學/工程學院/化學工程與材料科學學系/碩士(2012年)

摘要

目前L11-CoPt薄膜大多以MgO基板進行磊晶而獲得，但MgO基板價格昂貴，導致生產成本過高，所以在本研究中冀望以glass基板取代MgO基板。我們在超高真空的環境下，利用磁控濺鍍系統將等原子比的CoPt薄膜於350 ℃下濺鍍於非晶相的glass基材上，探討L11-CoPt薄膜在形成過程中的磁性質與微結構改變。
我們發現當CoPt薄膜直接濺鍍在glass基板上時，隨著CoPt薄膜厚度的增加，磁性質卻相對地減少，矯頑磁力(Hc)都低於0.5 kOe，且薄膜均呈現水平異向性。然而，在CoPt薄膜與基板之間插入Pt底層，磁性質有改善地趨勢，像是矯頑磁力與垂直異向性的提升。另外，改變具Pt底層的CoPt薄膜厚度，發現隨著厚度的下降，磁性質相對地提升，當膜厚降至3 nm時，Hc將提升至1.78 kOe。
為了更進一步地提升L11-CoPt的性質，我們對Pt底層進行了一系列的研究，首先我們更改Pt底層的退火時間(5 min~30 min)，接著Pt底層的退火溫度(200 ℃~500 ℃)，最後針對Pt底層的厚度進行改變(5 nm~30 nm)。綜合以上最佳化條件，得知當Pt底層厚度介於20 nm~25 nm之間，且於350℃下後退火15 min，
L11-CoPt薄膜具有最佳的Hc，約為2.49 kOe ~ 2.56 kOe。
本研究成功地以glass基板取代昂貴的MgO(111)單晶基板，將L11-CoPt薄膜鍍製於玻璃基板上，同時藉由CoPt與Pt底層的參數的改變大幅度提升CoPt薄膜的磁性質，本研究的結果可作為未來CoPt 薄膜導向商業應用的參考。

關鍵字

L11-鈷鉑 ； 水平異向性 ； 垂直異向性 ； 矯頑磁力

並列摘要

Most of current L11-CoPt thin films were deposited on MgO substrate for obtaining the epitaxially grown L11 structure. However, the ultrahigh price of MgO substrate does not match the manufacture process. In order to reduce the cost, this study investigated the replacement of MgO substrate with glass substrate. Samples were fabricated by magnetron sputtering under the ultra-high vacuum environment. The CoPt film was grown by rotational co-sputtering with equiatomic CoPt condition on an amorphous glass substrate at 350 ℃. The magnetic properties and microstructure of CoPt film on glass substrates were discussed.
In this study, CoPt film has lower coercivity (Hc~0.5 kOe) and in-plane magnetic anisotropy on glass substrate without inserting a Pt underlayer. When a Pt underlayer is added between magnetic film and glass substrate, the magnetic properties are obviousily improved, not only enhanced the coercivity but also altered the perpendicular anisotropy. Additional, the Hc of CoPt film is strongly increased with decreaseing the thickness of CoPt layer. When the thickness of CoPt is reduced to 3 nm, the coercivity is increase to 1.78 kOe. In order to further improve the magnetic properties of L11-CoPt, sputtering condition of Pt underlayer was systemly studied. First of all, we change the annealing time of Pt underlayer (5 min~30 min), and then the annealing temperature of Pt underlayer (200 ℃ ~ 500 ℃), and aim the thickness to adjust (5 nm ~ 30 nm). The optimun conditions for depositing Pt unserlayer are 20 nm to 25 nm and annealing at 350 ℃ for 15 min, at this condition the L11-CoPt film obtains the higher Hc of 2.49 kOe ~2.56 kOe.
Glass substrate replaces expensive MgO(111) substrate in our study. Except successfully fabricate L11-CoPt on glass, we also enhance the magnetic properies of CoPt film by adjusting the sputtering condition of Pt underlayer. The presented results have great potential for future magnetic recording midea application.

並列關鍵字

L11-CoPt ； in-plane magnetic anisotropy ； perpendicular anisotropy ； coercivity

參考文獻

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