Engineering metal oxidation using epitaxial strain
Engineering metal oxidation using epitaxial strain
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DOI：
10.1038/s41565-023-01397-0
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发表时间：
2023-05-22
影响因子：
38.3
通讯作者：
Jalan, Bharat
中科院分区：
文献类型：
--
作者：
Nair, Sreejith;Yang, Zhifei;Jalan, Bharat
为了解决用超高真空合成含有难氧化金属的高质量单晶金属氧化物薄膜的问题，揭示了外延应变对金属氧化化学和薄膜生长的隐藏作用。由于自旋轨道耦合和电子关联能的微妙相互作用，铂族金属的氧化物在未来的电子和自旋电子学中具有广阔的应用前景。然而，由于它们的低蒸汽压和低氧化电位，它们作为薄膜的合成仍然具有挑战性。在这里，我们展示了如何使用外延应变作为控制旋钮，以加强金属氧化。以Ir为例，我们展示了外延应变在其氧化化学工程中的应用，即使使用相同的生长条件，也可以实现相纯的Ir或IrO2薄膜。用基于密度泛函理论的修正生成热框架对实验结果进行了解释，突出了金属-衬底外延应变在控制氧化物生成热容中的重要作用。我们还通过外延应变对Ru氧化的影响来验证这一原理的普遍性。我们工作中研究的IrO2薄膜进一步揭示了量子振荡，证明了良好的薄膜质量。我们提出的外延应变方法可以使用应变工程来生长难氧化元素的氧化膜。
A quest to resolve ultra-high vacuum synthesis of high-quality, single-crystalline metal oxide thin films containing hard-to-oxidize metals reveals a hidden role of epitaxial strain on the metal oxidation chemistry and resulting thin-film growth.The oxides of platinum group metals are promising for future electronics and spintronics due to the delicate interplay of spin-orbit coupling and electron correlation energies. However, their synthesis as thin films remains challenging due to their low vapour pressures and low oxidation potentials. Here we show how epitaxial strain can be used as a control knob to enhance metal oxidation. Using Ir as an example, we demonstrate the use of epitaxial strain in engineering its oxidation chemistry, enabling phase-pure Ir or IrO2 films despite using identical growth conditions. The observations are explained using a density-functional-theory-based modified formation enthalpy framework, which highlights the important role of metal-substrate epitaxial strain in governing the oxide formation enthalpy. We also validate the generality of this principle by demonstrating epitaxial strain effect on Ru oxidation. The IrO2 films studied in our work further revealed quantum oscillations, attesting to the excellent film quality. The epitaxial strain approach we present could enable growth of oxide films of hard-to-oxidize elements using strain engineering.