npj: 铁电材料大电-光常数—应变调控

Original npj 知社学术圈 2021-06-13

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电-光（EO）效应晶体的介电常数及其折射率可以在电场作用下发生改变的效应，可用来调控光的传播，是开发和优化光电器件的关键，在信息技术和计算技术领域极为重要。为提高EO设备效率和小型化，人们迫切希望找到具有大电光常数的材料，理解电光效应的增强机制。

来自美国阿肯色大学的Laurent Bellaiche 领导的团队，采用精确的从头算技术，研究了应变对于PbTiO₃这一经典铁电体电-光特性的影响，以企确定导致铁电PbTiO₃薄膜中高电光性能的一般机制。计算结果显示，应变工程可以有选择性的改进某个电-光常数，具体增强机制有两种：其一为利用拉伸应变实现相变边界处光学声子模式的软化；其二为利用压缩应变产生等效负压导致大的压电系数。他们通过计算预测出应变下可以产生大于100pm/V 的大电-光常数, 并且建议可以通过在硅这一技术上十分重要材料衬底上生长出PbTiO₃来获得大的r₃₃电-光系数，其数值可为常用的LiNbO₃ 电光材料的两倍。

该文近期发表于npj Computational Materials 5: 6 (2019)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Strain engineering of electro-optic constants in ferroelectric materials

Charles Paillard, Sergei Prokhorenko & Laurent Bellaiche

Abstract Electro-optic effects allow control of the ow of light using electric fields, and are of utmost importance for today’s information and communication technologies, such as TV displays and fiber optics. The search for large electro-optic constants in films is essential to the miniaturization and increased efficiency of electro-optic devices. In this work, we demonstrate that strain-engineering in PbTiO₃ films allows to selectively choose which electro-optic constant to improve. Unclamped electro-optic constants larger than 100 pm V⁻¹ are predicted, either by driving the softening of an optical phonon mode at a phase transition boundary under tensile strain, or by generating the equivalent of a negative pressure via compressive strain to obtain extremely large piezoelectric constants. In particular, a r₃₃ electro-optic coefficient twice as large as the one of the commonly used LiNbO₃ electro-optic material is found here when growing PbTiO₃ on the technologically important Si substrate.