Different surface preparation methods for cleaning MgO, a widely used substrate in oxide epitaxy, are summarized and compared. We find that in situ surface preparation methods are preferable to ex situ preparation methods. We show that the complete removal of hydroxide, carbonate, and adventitious carbon from the MgO surface can be achieved via oxygen plasma exposure at 200 °C without high temperature annealing. Using this process, an atomically flat surface with root mean square roughness values of ∼0.1 nm is demonstrated. Surfaces treated thus also exhibit sharp RHEED streaks indicating good crystalline order of the surface. We also show that high temperature annealing of MgO, either by itself or following other ex situ cleaning methods, such as solvent cleaning, is a reasonably effective method for the removal of surface contaminants, enabling one to achieve a surface roughness of ∼0.2 nm. We show that wet etching or other ex situ cleaning methods alone without annealing cannot eliminate all surface contaminants and may even worsen the surface roughness significantly.

中文翻译：

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通过氧等离子体制备清洁的 MgO 表面：与标准基板清洁程序的比较

总结和比较了用于清洁氧化物外延中广泛使用的衬底 MgO 的不同表面制备方法。我们发现原位表面制备方法优于异位制备方法。我们表明，可以通过在 200 °C 下暴露于氧等离子体而无需高温退火来完全去除 MgO 表面的氢氧化物、碳酸盐和外来碳。使用该过程，展示了均方根粗糙度值为 ~0.1 nm 的原子级平坦表面。因此处理过的表面也表现出尖锐的 RHEED 条纹，表明表面的结晶有序。我们还表明，MgO 的高温退火，无论是单独进行还是遵循其他非原位清洁方法，例如溶剂清洁，都是去除表面污染物的合理有效方法，使表面粗糙度达到~0.2 nm。我们表明，单独使用湿蚀刻或其他非原位清洁方法而不进行退火不能消除所有表面污染物，甚至可能显着恶化表面粗糙度。