Synthesis、microstructure and magnetic properties of Co-CoO nanocrystalline thin films
Date Issued
2005
Date
2005
Author(s)
Chou, You-Jing
DOI
en-US
Abstract
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.
Subjects
鈷
氧化鈷
交換耦合力
奈米晶粒薄膜
Co
CoO
exchange coupling
nanocrystallin film
Type
thesis
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