外延PbZ_(r0.2)Ti_(0.8)O_(3)薄膜负电容的应变调控

Strain tuning of negative capacitance in epitaxial PbZ_(r0.2)Ti_(0.8)O_(3) thin films

为了让摩尔定律能够延续下去,降低功耗是很多研究者关注的问题,铁电负电容效应的发现为其提供了一种解决方案.应变工程作为调控铁电薄膜物理性能的有效手段已经被广泛研究.但是应变对铁电负电容调控的相关机理并不清楚.本文通过Landau-Khalatnikov方程模拟了应变场和温度场对PbZ_(r0.2)Ti_(0.8)O_(3)铁电薄膜负电容的影响.研究表明,瞬态负电容的产生伴随着极化的翻转,在一定温度下压应变有助于铁电负电容的稳定,而在张应变下铁电极化翻转较快,负电容效应持续时间较短.但是,增加的压应变会导致对应的矫顽电压增大,需要更大的外电压才能使极化翻转,从而产生负电容.此外,在恒定的应变下,温度越低,负电容效应越显著.本工作对未来负电容微纳器件的设计具有一定的指导意义.

In order to continue Moore’s Law,the reducing of power consumption is concerned by many researchers,and the discovery of ferronegative negative capacitance effect(NCE)provides a solution.Strain engineering has been widely studied as an effective means to regulate the physical properties of ferroelectric thin films.But the relevant mechanism of strain to ferroelectric negative capacitance regulation is not clear.Recently,the experimental results have shown that it is possible to stabilize the transient NCE in resistance-ferroelectric networks.In this work,we use the Landau-Khalatnikov theory to study the microscopic domain evolution and the influence of strain and temperature on NCE in a ferroelectric film.It is shown that compressive strain enhances NCE while NCE becomes weaker under a tensile strain.However,a larger compressive strain will give rise to a higher coercive voltage that hinders the NCE from forming.In addition,under a certain strain,the NCE becomes stronger at lower temperature.This work provides the theoretical basis for designing the negative capacitance devices and scaling towards nanoscale dimensions in future.