Tracking the emergence of epitaxial metal–oxide interfaces from precursor alloys,Nanoscale

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Tracking the emergence of epitaxial metal–oxide interfaces from precursor alloys
Nanoscale ( IF 5.8 ) Pub Date : 2021-09-08 , DOI: 10.1039/d1nr03492h
Yu Wen _{1,

2} , Hideki Abe _{3,

4} , Kazutaka Mitsuishi ₁ , Ayako Hashimoto _{1,

2,

5}

Affiliation

Heterointerfaces with an epitaxial relationship, self-assembled nanocomposites of Pt(111)/CeO₂(111) 60°, were successfully formed by simple oxidation of Pt₅Ce alloy. Oxygen dissolution into the alloy causes spacial periodic compositional perturbation by atomic segregation, specifically, by local diffusion of Pt and Ce atoms. A striped pattern of Pt and CeO₂ with a 4–5 nm periodicity formed through phase transformation of the Pt-rich alloy and oxidation of the Ce-rich alloy, respectively. Notably, a fully epitaxial relationship between the Pt and CeO₂ phases was observed even in the initial stage. With continued annealing, the crystals rotated into an energetically favorable orientation with respect to the remaining (111)Pt//(111)CeO₂. The alloy oxidation and its resulting nanoscale phase-separation behavior were verified in an ex situ annealing experiment of an alloy specimen, which had been first thinned by a focused ion beam. Changing the oxygen partial pressure to the reaction interface may alter the orientation relationship between the hexagonal close-packed Pt₅Ce structure and face-centered cubic Pt/CeO₂ structure, thereby altering the growth direction of the separated phases. These findings present a pathway for the self-assembly of epitaxial Pt(111)/CeO₂(111) interface and are expected to assist the structural design of metal–oxide nanocomposites.

中文翻译：

追踪前体合金中外延金属-氧化物界面的出现

通过简单氧化 Pt ₅ Ce 合金，成功形成了具有外延关系的异质界面，即 Pt(111)/CeO ₂ (111) 60°的自组装纳米复合材料。氧溶解到合金中会通过原子偏析，特别是通过 Pt 和 Ce 原子的局部扩散引起空间周期性成分扰动。分别通过富铂合金的相变和富铈合金的氧化形成具有 4-5 nm 周期的 Pt 和 CeO ₂条纹图案。值得注意的是，即使在初始阶段，也观察到Pt 和 CeO ₂相之间的完全外延关系。随着继续退火，晶体旋转到相对于剩余的 (111)Pt//(111)CeO 能量有利的方向₂ . 合金氧化及其产生的纳米级相分离行为在合金样品的非原位退火实验中得到验证，合金样品首先被聚焦离子束减薄。改变反应界面的氧分压可能会改变六方密排Pt₅ Ce结构与面心立方Pt/CeO₂结构之间的取向关系，从而改变分离相的生长方向。这些发现为外延 Pt(111)/CeO₂ (111) 界面的自组装提供了一条途径，有望帮助金属氧化物纳米复合材料的结构设计。

更新日期：2021-09-15

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