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標題: | 鈷-氧化鈷奈米晶粒薄膜之製作
與微結構及磁性質分析 Synthesis、microstructure and magnetic properties of Co-CoO nanocrystalline thin films |
作者: | You-Jing Chou 周佑靜 |
指導教授: | 郭博成 |
共同指導教授: | 林昭吟 |
關鍵字: | 鈷,氧化鈷,交換耦合力,奈米晶粒薄膜, Co,CoO,exchange coupling,nanocrystallin film, |
出版年 : | 2005 |
學位: | 碩士 |
摘要: | 本研究乃利用射頻(RF)反應濺鍍法製作鈷-氧化鈷(Co-CoO)奈米結晶顆粒薄膜,量測的樣品是用濺鍍的方式在矽基板(100)表面製作薄膜。這個實驗中我們分成兩部分,第一部分製作純鈷薄膜,不同的濺鍍速度下得到不同晶粒大小的純鈷薄膜,並研究濺鍍在不同的基板溫度上,磁性性質的變化。第二部分我們調整通入的氧氣分壓,製作鈷-氧化鈷薄膜,控制氧分壓以及利用不同的濺鍍速率,來製備不同晶粒大小的Co-CoO薄膜,研究其磁性的改變並研究其結構上的差異,藉由鐵磁/反鐵磁 (FM/AFM)界面的耦合力來提升頑磁力(coericivity)並產生交換偏壓的效應。
測量的結果顯示,在純鈷的薄膜上,晶粒的大小對頑磁力有很大的影響,利用基板溫度使晶粒長大的薄膜,雖然頑磁力增加,可是殘磁力(Mr)卻因此減小,當基板溫度大於300℃時,結構上也從六方緊密堆積(HCP)轉變成面心立方體(FCC)。在鈷與氧化鈷的薄膜上,我們也同樣發現晶粒大小對頑磁力的影響。同時,添加氧分壓會使頑磁力大幅的增加,並且由於氧化鈷的存在,會產生交換偏壓。結果顯示在氧氣對氬氣比例為百分之二,鍍膜速率為 3.4 nm/min時,得到最佳的結果。 Co-CoO nanocrystalline films are synthesized by RF reactive sputtering method. The films are deposited on Si (100) substrate. There are two parts in this work: first, we deposit pure Co films with different grain sizes by controlling the deposition rate. In addition, we also deposit Co on Si (100) with different substrate temperature. Second, we adjust the appropriate input oxygen/argon pressure, and deposit Co-CoO nano-crystallline films. With different oxygen/argon ratio and different deposition rates, we can control grain size in certain range. The addition of CoO enhances coercivity of Co greatly, and it is due to the exchange coupling between Co and CoO. We also investigate the correlation between exchange bias and the microstructure of the thin films. In Co films, the results show that the increase of coercivity is related to grain size. The films deposited at high substrate temperature have the larger grains and show the same trend. However, the remanence decreases as the substrate temperature increases. Moreover, the structure of thin films is transformed from HCP to FCC as the substrate temperature is raised up to 300 ℃. In Co-CoO films, we observe a nanostructure-dependency of coercivity. The addition of oxygen pressure enhances coercivity greatly. Exchange bias stems from the coexistence of CoO and Co. The best exchange bias in our films occurs when the O2/Ar ratio= 2% and the deposition rate was 3.4 nm/min, which is related to an effective nanostructure of Co-CoO. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/35981 |
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顯示於系所單位: | 材料科學與工程學系 |
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