Ab initio phase diagrams of Hf–O, Zr–O and Y–O: a comparative study,Faraday Discussions

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Ab initio phase diagrams of Hf–O, Zr–O and Y–O: a comparative study
Faraday Discussions ( IF 3.3 ) Pub Date : 2018-07-24 , DOI: 10.1039/c8fd00104a
Konstantin Z. Rushchanskii _{1,

2,

3,

4} , Stefan Blügel _{1,

2,

3,

4} , Marjana Ležaić _{1,

2,

3,

4}

Affiliation

We present phase diagrams of binary oxides, Hf–O, Zr–O and Y–O, obtained by ab initio evolutionary simulations, in order to explore possible metastable crystalline suboxide structures which could be quenched during the electroforming processes within the conductive filaments in stoichiometric HfO₂, ZrO₂ and Y₂O₃ host materials, in resistive switching devices. We find that, in the range MO–MO₂ (where M = Hf, Zr, Y), the most energetically favourable atomic configurations have properties which facilitate the ionic conduction of oxygen. Namely, the calculations reveal that oxygen vacancies tend to order in arrays of one-dimensional channels, along which the migration barrier of anions is much lower than for the stoichiometric hosts. We explore for Hf–O and Zr–O a new set of structural patterns, different from those of the host materials, for which a change of oxygen stoichiometry does not change the underlying structural frame. However, a sufficient change of oxygen stoichiometry drives metallic conductivity in oxygen-deficient compounds, whereas their oxygen-rich counterparts are insulating. In contrast to Hf–O and Zr–O, in the Y–O system we find an atomic structure with metallic conductivity, which has the same structural frame as the stoichiometric Y₂O₃ host. We believe that this property enables the forming-free resistive switching in Y₂O₃.

中文翻译：

Hf-O，Zr-O和Y-O的从头算相图：对比研究

我们提供了从头算进化模拟获得的二元氧化物Hf-O，Zr-O和Y-O的相图，以探索可能的亚稳态结晶亚氧化物结构，该结构在化学计量的导电丝内进行电铸过程中可能会被淬灭在电阻开关装置中，HfO ₂，ZrO ₂和Y ₂ O ₃主体材料。我们发现，在MO–MO ₂范围内（其中M ＝ Hf，Zr，Y），最有利于能量的原子构型具有促进氧离子传导的性质。即，计算表明，氧空位倾向于在一维通道的阵列中有序排列，沿着该通道，阴离子的迁移势垒比化学计量的主体低得多。我们为Hf-O和Zr-O探索了一组新的结构模式，这些结构模式不同于主体材料，因为氧化学计量学的变化不会改变其基本的结构框架。但是，氧化学计量的充分变化会驱动缺氧化合物中的金属电导率，而它们的富氧对应物却是绝缘的。与Hf–O和Zr–O相比，在Y–O系统中，我们发现了具有金属电导率的原子结构，₂ O₃主机。我们相信，该性质使得能够在Y₂ O_3中进行无成形的电阻切换。

更新日期：2019-02-19

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