通过对称性工程在二氧化硅中构建铁电性
Symmetry-engineering ferroelectricity in silicon dioxides
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中文总结 AI 辅助
本文提出通过对称性工程在二氧化硅等非极性材料中构建铁电性，利用薄膜表面或单轴应变打破晶体对称性，实现低势垒室温铁电开关，为硅基芯片集成铁电体提供新方向。
中文摘要 AI 辅助
经典铁电性有一条长期确立的规则：任何铁电晶体必须采用10种特定极性点群之一。本文预测了一种独特的铁电性，其可在属于非极性非中心对称群的某些晶体中产生，该原理适用于包括二氧化硅（最广泛使用的介电材料）在内的许多体系。二氧化硅的大多数晶相不属于极性群，而非线性Si-O-Si构型会产生多个相同状态。我们通过第一性原理证明，可通过薄膜中的平行表面或施加单轴应变打破禁止极化形成的晶体对称性，使多个相同状态具有不同方向的极化，且可通过这些状态间的转变实现低势垒铁电开关，该开关在室温下可稳定至1纳米的厚度。我们的发现不仅能实现直接集成在硅芯片中的铁电体的低成本大规模制造，还为在普遍存在的非极性材料中探索铁电性开辟了新途径。
英文摘要
It is a long-established rule for classical ferroelectricity that any ferroelectric crystal must adopt one of the 10 specific polar point groups. Here we predict a unique type of ferroelectricity that can be generated in some crystals belonging to nonpolar noncentrosymmetric groups. This principle can be applicable to many systems including silicon dioxides, the most widely used dielectric materials. Most of their crystalline phases do not belong the polar groups, while the nonlinear Si-O-Si configurations lead to multiple identical states. We show first-principles evidence that the crystal symmetry forbidding the formation of polarizations, can be broken by either parallel surfaces in thin-films or applying a uniaxial strain. As a result, the multiple identical states are endowed with polarizations of different directions, and low-barrier ferroelectric switching can be realized via transition between them, which can be room-temperature robust down to the thickness of 1 nm. Our findings may not only enable low-cost and large-scale manufacture of ferroelectrics directly integrated in silicon chips, but also open a new avenue for exploring ferroelectricity in prevalent nonpolar materials.
