Abstract The degradation of the MgO thin film barrier of magnetic tunneling junctions caused by the dissolution of the film in deionized water during manufacturing processes is critical to the performance of spintronic devices. In this work, the influence of gas atmospheres including oxygen (O2), nitrogen (N2) and carbon dioxide (CO2) on dissolution behavior of the film was investigated by using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic absorption spectroscopy (AAS). XPS depth profile results reveal that deionized water reacts with the film and infiltrates into the deeper layer of the film resulting in the chemical transformation of MgO to Mg(OH)2. AAS results confirm that the films dissolve because Mg2+ ions are released into deionized water. Consequently, Mg concentration in deionized water increases. It is found that the concentration of Mg2+ ions in deionized water is highest in the dissolution of CO2-saturated deionized water and lowest in those of N2-saturated deionized water. Simultaneously, the release of Mg2+ causes the development of the coral-like clusters over their surface and a decrease of the film thickness. XPS depth profile and SEM cross-sectional results demonstrate that the film thickness slightly decreases in sample N2 and decreases considerably in sample CO2. This is due to the fact that CO2 gas reacts with water, reducing its pH and thus increasing of the dissolution rate, while N2 gas has no reaction with water. Finally, this work proposes a qualitative model based on chemical reaction to explain the dissolution behavior of the film.

中文翻译：

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气体气氛对去离子水降解氧化镁薄膜磁性隧道结的影响

摘要 制造过程中薄膜在去离子水中溶解导致磁性隧道结的 MgO 薄膜势垒退化，这对自旋电子器件的性能至关重要。在这项工作中，使用 X 射线光电子能谱 (XPS)、扫描电子显微镜 (SEM) 研究了包括氧气 (O2)、氮气 (N2) 和二氧化碳 (CO2) 在内的气体气氛对薄膜溶解行为的影响。和原子吸收光谱 (AAS)。XPS 深度剖面结果表明，去离子水与薄膜反应并渗入薄膜的深层，导致 MgO 化学转化为 Mg(OH)2。AAS 结果证实薄膜溶解是因为 Mg2+ 离子被释放到去离子水中。因此，去离子水中的镁浓度增加。发现去离子水中Mg2+离子浓度在CO2饱和去离子水中溶解度最高，在N2饱和去离子水中溶解度最低。同时，Mg2+ 的释放导致珊瑚状簇在其表面形成并降低薄膜厚度。XPS 深度分布图和 SEM 横截面结果表明，样品 N2 的膜厚度略有降低，而样品 CO2 的膜厚度显着降低。这是因为 CO2 气体与水反应，降低其 pH 值，从而增加溶解速率，而 N2 气体与水不反应。最后，这项工作提出了一个基于化学反应的定性模型来解释薄膜的溶解行为。