Negative capacitance regime in ferroelectrics demystified from nonequilibrium molecular dynamics
Negative capacitance regime in ferroelectrics demystified from nonequilibrium molecular dynamics
复制标题
DOI：
10.1103/physrevb.102.134101
复制
发表时间：
2020-10-02
影响因子：
3.7
通讯作者：
Ponomareva, I
中科院分区：
文献类型：
--
作者：
Lynch, K. A.;Ponomareva, I
铁电体中的负电容区与极化对电场的依赖性的负斜率有关，并且被平衡热力学定律所禁止。最近，它发展成为一个有争议但非常富有成效的领域，有望成为下一代低功率晶体管。至少在某种程度上，这些争议是由于缺乏对这种现象的机制的直接实验见解而引起的。虽然实验的洞察力，确实是具有挑战性的，目前，我们探测铁电PbTiO 3散装和薄膜与现实的第一性原理为基础的非平衡分子动力学模拟模型最密切的实验条件下的效果。从模拟中得出以下见解：（i）铁电体即使在极端的电场施加速率下也不会进入磁禁区;（ii）当补偿电荷稀缺或被外部电路减慢时，负斜率自然出现;（iii）负斜率很好地控制了所施加的阶跃脉冲场和屏蔽电荷量之间的相互作用。后者可用于设计负电容机制。
Negative capacitance regime in ferroelectrics is associated with the negative slope in the dependence of the polarization on electric field and is prohibited by the laws of equilibrium thermodynamics. Very recently, it developed into a controversial but very productive area with a promise for next generation low-power transistors. At least, in part, the controversies arise from the lack of direct experimental insight into the mechanism for such phenomena. Although the experimental insight is, indeed, challenging at present, we probe the effect in ferroelectric PbTiO3 bulk and a thin film with realistic first-principles-based nonequilibrium molecular dynamics simulations which model most closely experimental conditions. The following insights emerge from the simulations: (i) the ferroelectric never enters the thermodynamically forbidden region even under extreme rates of electric-field application; (ii) the negative slope naturally arises when the compensating charge is either scarce or slowed down by the external circuitry; (iii) the negative slope is well controlled by the interplay between the applied step pulse field and the amount of the screening charge. The latter can be used to design the negative capacitance regime.