Initial atomic-scale oxidation pathways on a Ni–15Cr(100) alloy surface
Initial atomic-scale oxidation pathways on a Ni–15Cr(100) alloy surface
复制标题
Ni–15Cr(100) 合金表面的初始原子级氧化途径
DOI：
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发表时间：
2021
影响因子：
5.1
通讯作者：
P. Reinke
中科院分区：
文献类型：
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作者：
William H. Blades;Matthew R. Barone;P. Reinke
为了了解初始氧化过程背后的原子现象，我们使用扫描隧道显微镜/光谱学（STM/STS）研究了在 Ni-15 wt%Cr(100) 合金表面形成完整层之前氧化物生长的纳米级演化。在氧化开始时，氧化镍超晶格在台阶边缘形成氧化物楔形，最终在台阶上生长。 NiO 层完成后，下一层的成核总是从超晶格的凹槽位置开始。 Cr 氧化物的形成在氧化过程的早期以盘状氧化物颗粒的形式开始，蒙特卡洛模拟显示这可能是由合金表面的 Cr 聚集引起的。进一步氧化后，观察到 Cr(100)-p(2 × 2)O 重构表面，表明 Cr 的相分离预示着钝态 Cr 氧化膜的形成。 STS 结果在氧化物-合金界面以及每种氧化物之间各不相同，从而可以更深入地了解电子异质性的起源及其对氧化物生长的影响。利用这些数据，我们提出了一个氧化模型，该模型强调了卡布雷拉-莫特之前状态下 Ni-Cr(100) 合金上部分氧化层的生长。
To understand the atomistic phenomenon behind initial oxidation processes, we have studied the nanoscale evolution of oxide growth prior to the formation of a complete layer on a Ni–15 wt%Cr(100) alloy surface using scanning tunneling microscopy/spectroscopy (STM/STS). At the onset of oxidation, a NiO superlattice forms oxide wedges across the step edges, eventually growing across the terraces. The completion of the NiO layer is followed by nucleation of the next layer, which always commences at the groove site of the superlattice. The Cr-oxide formation initiates as disk-shaped oxide particles early in the oxidation process, which Monte Carlo simulations reveal are likely caused by Cr clustering across the alloy surface. Upon further oxidation, a Cr(100)-p(2 × 2)O reconstructed surface is observed, indicating phase separation of Cr predicates the formation of the passive Cr-oxide film. The STS results vary across the oxide–alloy interface and between each oxide, providing greater insight into the origins of electronic heterogeneity and their effect on oxide growth. Using these data, we propose an oxidation model that highlights the growth of partial oxide layers on Ni–Cr(100) alloys within the pre-Cabrera–Mott regime.