Effect of Dopant Ordering on the Stability of Ferroelectric Hafnia,Physica Status Solidi-Rapid Research Letters

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Effect of Dopant Ordering on the Stability of Ferroelectric Hafnia
Physica Status Solidi-Rapid Research Letters ( IF 2.5 ) Pub Date : 2020-03-23 , DOI: 10.1002/pssr.202000047
Sangita Dutta _{1,

2} , Hugo Aramberri ₁ , Tony Schenk ₁ , Jorge Íñiguez _{1,

2}

Affiliation

Films of the all‐important compound hafnia (HfO₂) can be prepared in an orthorhombic ferroelectric (FE) state that is ideal for applications, e.g., in memories or negative‐capacitance field‐effect transistors. The origin of this FE state remains a mystery, though, as none of the proposed mechanisms for its stabilization—from surface and size effects to formation kinetics—is fully convincing. Interestingly, it is known that doping HfO₂ with various cations favors the occurrence of the FE polymorph; however, existing first‐principles works suggest that doping by itself is not sufficient to stabilize the polar phase over the usual nonpolar monoclinic ground state. Herein, first‐principles methods are used to re‐examine this question. Two representative isovalent substitutional dopants, Si and Zr, are considered, and their preferred arrangement within the HfO₂ lattice is studied. The results reveal that small atoms like Si can adopt very stable configurations (forming layers within specific crystallographic planes) in the FE orthorhombic phase of HfO₂ but comparatively less so in the nonpolar monoclinic one. Further, it is found that, at low concentrations, such a dopant ordering yields a FE ground state, the usual paraelectric phase becoming a higher‐energy metastable polymorph. The implications of the findings are discussed.

中文翻译：

掺杂顺序对铁电氧化Ha稳定性的影响

可以以正交晶体铁电（FE）状态制备最重要的复合氧化hom（HfO ₂）薄膜，该薄膜非常适合用于例如存储器或负电容场效应晶体管中的应用。然而，这种有限元状态的起源仍然是个谜，因为从表面和尺寸效应到地层动力学的拟议中的稳定机制都没有完全说服力。有趣的是，已知掺杂HfO ₂具有各种阳离子有助于形成FE多晶型物；然而，现有的第一性原理研究表明，掺杂本身不足以使极性相稳定在通常的非极性单斜基态之上。在这里，首先原则方法被用来重新检查这个问题。考虑了两个代表性的等价取代掺杂剂Si和Zr，并研究了它们在HfO ₂晶格中的优选排列。结果表明，像Si这样的小原子在HfO _2的斜方晶相中可以采用非常稳定的结构（在特定的晶面内形成层）但相对而言，在非极性单斜井中则相对较少。此外，发现在低浓度下，这种掺杂剂排序会产生FE基态，通常的顺电相变成能量更高的亚稳多晶型物。讨论的结果的含义。

更新日期：2020-03-23

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