缺陷纤锌矿 α-Al2S3 中的四阱铁电性与适中开关势垒：一项第一性原理研究
Quadruple-well ferroelectricity and moderate switching barrier in defective wurtzite α-Al2S3: a first-principles study
AI总结：
该研究通过第一性原理计算发现，阳离子空位有序的纤锌矿 α-Al2S3 具有单轴四阱铁电性和较低开关势垒，应变与 Ga 掺杂还可进一步降垒。
摘要：
纤锌矿型铁电体因其铁电性质以及与现有半导体的集成能力，在下一代微电子器件中极具前景。然而，其接近击穿电场的高矫顽场需要被降低。为解决这一问题并确保器件可靠性，研究者已投入大量精力探索具有更低极化反转势垒的新型纤锌矿化合物，并实施掺杂策略。本文报道了关于阳离子空位有序纤锌矿 α-Al2S3 中极化反转的第一性原理计算，揭示了其单轴四阱铁电性以及 51 meV/cation 的适中开关势垒，该势垒远低于传统纤锌矿铁电体。Al 空位具有三个与这种非同寻常的四阱铁电性和适中开关势垒相关的重要特征：缓解阳离子—阳离子排斥、具备可减轻面内晶格膨胀的结构柔性，以及形成由 Al 3pz 和 S 3pz 轨道组成的类 σ 键合态。双轴压缩应变和 Ga 掺杂可将开关势垒降低至多 40%。本研究鼓励对缺陷纤锌矿 α-Al2S3 的铁电性质开展实验研究，将其作为具有非传统且引人关注铁电性的新型潜力材料，并提出了一种降低纤锌矿铁电体开关势垒的潜在策略：引入阳离子空位。
英文摘要：
Wurtzite-type ferroelectrics are highly promising for next-generation microelectronic devices due to their ferroelectric properties and integration with exiting semiconductors. However, their high coercive fields, which are close to breakdown electric fields, need to be lowered. To deal with this issue and secure device reliability, much effort has been devoted to exploring novel wurtzite compounds with lower polarization switching barriers and implementing doping strategies. Here, we report first-principles calculations on polarization switching in cation-vacancy ordered wurtzite α-Al2S3, unveiling its uniaxial quadruple-well ferroelectricity and moderate switching barrier, 51 meV/cation, which is much lower than that of conventional wurtzite ferroelectrics. There are three important features relevant to the Al vacancies leading to the uncommon quadruple-well ferroelectricity and the moderate switching barrier: mitigation of cation-cation repulsion, structural flexibility that alleviates an in-plane lattice expansion, and formation of σ-like bonding states consisting of Al 3pz and S 3pz orbitals. Biaxial compressive strain and Ga doping lower the switching barriers by up to 40%. This study encourages experimental investigation of the ferroelectric properties for defective wurtzite α-Al2S3 as a new promising material with unconventional and intriguing ferroelectricity and suggests a potential strategy for reducing switching barriers in wurtzite ferroelectrics: introducing cation vacancies.
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