Nonvolatile Ferroelastic Strain from Flexoelectric Internal Bias Engineering
Nonvolatile Ferroelastic Strain from Flexoelectric Internal Bias Engineering
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DOI：
10.1103/physrevapplied.17.024013
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发表时间：
2022-02
影响因子：
4.6
通讯作者：
W. Hou;S. Chowdhury;Aditya Dey;C. Watson;Tara Peña;Ahmad Azizimanesh;H. Askari;Stephen M. Wu
中科院分区：
文献类型：
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作者：
W. Hou;S. Chowdhury;Aditya Dey;C. Watson;Tara Peña;Ahmad Azizimanesh;H. Askari;Stephen M. Wu
铁电材料中的内部偏置是一种众所周知的现象，其使铁电极化滞后回线沿电场轴沿着偏移。对这种自由度的控制可能会导致铁电器件的替代类别，就像对铁磁器件中交换偏置的类似概念的控制一样。目前，缺乏一个系统的方法来工程内部偏置的设计，允许设备通过设备控制这个参数，导致难以将这些概念转化为大规模集成的铁电电子。在这项工作中，挠曲电效应是用来工程师的内部偏置通过受控沉积的应力薄膜铁电体。随着薄膜力的增加（薄膜应力×薄膜厚度），通过沉积应力薄膜应变片，在铁电单晶表面附近产生大的应变梯度。使用这种技术，可以连续地调谐内部偏置以控制由铁电体施加的铁弹性应变与施加的电场，从而实现对铁弹性非易失性的控制。通过密度泛函理论和有限元分析，使用没有自由参数的模型，这符合预期的幅度和方向性的flexoelectric场，然后进一步证实piezoresponse力显微镜的内部偏置的Flexoelectric控制进行验证。这种应力诱导的挠曲电效应利用了商业互补金属氧化物半导体（CMOS）工业制造工艺已经广泛采用的流行应变工程技术，因此在可扩展性和可靠性方面具有优势。利用这些技术可以导致在铁电场效应或应变电子器件中的非易失性的器件级控制。
Internal bias in ferroelectric materials is a well-known phenomenon that offsets the ferroelectric polarization hysteresis loop along the electric-field axes. Control over this degree of freedom could lead to alternative classes of ferroelectric devices, as with control over the analogous concept of exchange bias in ferromagnetic devices. Currently, there lacks a systematic approach to engineering internal bias by design that allows for device-by-device control over this parameter, leading to difficulty in translating these concepts to the large-scale integration of ferroelectric electronics. In this work, the flexoelectric effect is used to engineer internal bias through the controlled deposition of stressed thin films onto ferroelectrics. Large strain gradients are generated near the surface of ferroelectricsingle crystals through the deposition of stressed thin film strain gauges with increasing film force (film stress × film thickness). Using this technique, it is possible to continuously tune internal bias to control ferroelastic strain applied by the ferroelectric versus applied electric field, thereby achieving control of ferroelastic nonvolatility. Flexoelectric control of internal bias is verified by density functional theory and finite element analysis using a model with no free parameters, which matches both the expected magnitude and directionality of the flexoelectric field, and then further confirmed by piezoresponse force microscopy. This stress-induced flexoelectric effect utilizes popular strain engineering techniques already widely adopted by commercial complementary metal-oxide-semiconductor (CMOS) industrial fabrication processes, therefore sharing its advantages in scalability and reliability. Utilizing these techniques may lead to device-by-device level control of nonvolatility in ferroelectric field-effect or straintronic devices.