Oxidation kinetics of thin and ultrathin cobalt films
Oxidation kinetics of thin and ultrathin cobalt films
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钴薄膜和超薄薄膜的氧化动力学
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
W. Zinn
中科院分区：
文献类型：
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作者：
L. Smardz;U. Köbler;W. Zinn
我们在外延氧化的Si（111）表面制备了多晶Co薄膜，并利用金属钴是铁磁体而CoO是反铁磁体，因此实际上是非磁性的这一事实，研究了它们在大气条件下的氧化动力学。因此，氧化与磁性损失有关。结果表明，所有初始厚度为di ~ 5nm的样品几乎都在瞬间氧化，其中2.5 nm的金属被一定量地转化为氧化物。当di < 5 nm时，氧化时间常数显著增加，并随膜厚度的减小近似线性相关，当di→0时达到外推值τ=190天。这个增加的时间常数使得所有di < 2.5 nm的样品在本研究过程中由于非氧化的金属休息而呈现铁磁性。俄歇电子能谱分析表明，氧化产物主要是CoO，特别是靠近金属界面的部分，但其他部分都是CoO。
We have prepared polycrystalline Co films on epitaxially oxidized Si(111) surfaces and studied their oxidation kinetics under atmospheric conditions using the fact that metallic cobalt is a ferromagnet but CoO is an antiferromagnet and therefore practically nonmagnetic. As a consequence, oxidation is associated with a loss in magnetism. Results show that all samples with an initial thickness of di ≳ 5 nm oxidize practically instantaneously, whereby a constant amount of 2.5 nm of metal is transformed into oxide. For di < 5 nm the time constant for oxidation increases considerably and follows an approximately linear dependence with decreasing film thickness, reaching an extrapolated value of τ=190 days for di → 0. This increasing time constant let all samples with di < 2.5 nm appear ferromagnetic within the course of this study due to a nonoxidized metallic rest. Auger electron spectroscopy analyses revealed that the main oxidation product is in fact CoO, especially near to the metal interface, but that oth...