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.

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/光谱法（STM / STS）研究了在Ni–15 wt％Cr（100）合金表面上形成完整层之前氧化物生长的纳米级演变。 ）。在氧化开始时，NiO超晶格在台阶边缘形成氧化物楔，最终在台阶上生长。NiO层完成后，下一层的形核将始终在超晶格的凹槽位置开始。铬氧化物的形成是在氧化过程的早期以圆盘状氧化物颗粒开始的，蒙特卡罗模拟显示这很可能是由于整个合金表面的铬团簇引起的。进一步氧化后，观察到Cr（100）-p（2×2）O重建的表面，Cr的相分离表明钝化Cr氧化膜的形成。STS结果在整个氧化物-合金界面之间以及每个氧化物之间都各不相同，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，该模型突出了在Cabrera-Mott之前的Ni-Cr（100）合金上部分氧化物层的生长。