Enhanced Ferroelectric Functionality in Flexible Lead Zirconate Titanate Films with In Situ Substrate‐Clamping Compensation

Abstract

Much attention has recently been given to flexible and wearable integrated electronic devices, with a strong emphasis on real‐time sensing, computing, and communication technologies. Thin ferroelectric films exhibit switchable polarization and strong electromechanical coupling, and hence are in widespread use in such technologies, albeit not when flexed. Effects of extrinsic strain on thin ferroelectric films are still unclear, mainly due to the lack of suitable experimental systems that allow cross structural–functional characterization with in situ straining. Moreover, although the effects of intrinsic strain on ferroelectric films, e.g., due to film–substrate lattice mismatch, have been extensively investigated, it is unclear how these effects are influenced by external strain. A method to strain thin films homogenously in situ is developed, allowing structural characterization as well as functional switching and piezorsponse measurements at the nanoscale, while retaining the sample under constant straining conditions. Using this method, thin films of PbZr0.2Ti0.8O3, which were grown on a flexible mica substrate, are strained to reduce substrate clamping effects and increase the tetragonality. Consequently, the domain stability is increased, the coercive field value is decreased, and imprint effects are reduced. This method also allows direct characterization of the relationship between the lattice parameters and nanoscale properties of other flexible materials.

Highly Robust Flexible Ferroelectric Field Effect Transistors Operable at High Temperature with Low‐Power Consumption

“…No significant change in P‐E loops measured under a series of bending radii ( R = +∞, 10, 8, 6, 4 mm) is observed, suggesting that the mica/CFO/SRO/PZT/Pt capacitor is stable with bending radius as small as 4 mm. No obvious change in domain structure is observed under bending either, as shown in Figure S4 in the Supporting Information, though different observation has also been reported in literature . Furthermore, cyclic bending test with a bending radius of 6 mm was carried out for 500 cycles, resulting in no appreciable degradation in its ferroelectricity as shown in Figure e.…”

Flexible ferroelectric wearable devices for medical applications

“…This kind of material can be divided in non-centrosymmetric crystal structure inorganic materials and in semi-crystalline polymeric materials. The former class includes ferroelectric materials such as lead titanate (PbTiO 3 ), lead zirconate titanate (PbZrTiO 3 ) ( Dagdeviren et al, 2014 , 2015 ) and modified lead zirconate titanate (PbZr x Ti 1−x O 3 ) ( Winestook et al., 2019 ), barium titanate (BaTiO 3 ) ( Guan et al., 2020 ), strontium bismuth titanate (SrBi 4 Ti 4 O 15 ), potassium sodium niobate ( Bairagi and Ali, 2020 ), and potassium niobate (KNbO 3 ) ( Yang et al., 2012 ). On the other hand, piezoelectric polymers for pressure/strain sensing consist of polypropylene ferroelectret (PPFE) ( Wu et al., 2015 ), where dipoles originate from electrically charged pores, and ferroelectric polymers such as polyvinylidene fluoride PVDF ( Chiu et al., 2013 ) and P(VDF-TrFE) ( Chen et al, 2015 ).…”

Giant Superelastic Piezoelectricity in Flexible Ferroelectric BaTiO3 Membranes

“…Modern applications of piezoelectrics hinge on thin films; − however, the substrate in such geometries is typically rigid, preventing the development of flexible devices. Flexible piezoelectric devices are therefore based on either nanowires or thin-film systems but with substrates that have been designed especially for such applications. , Most piezoelectric applications rely on lead-based materials, which exhibit strong piezoelectric coefficients. Nevertheless, the toxicity of these materials is undesirable for environmental considerations, whereas it also disqualifies them for medical or wearable applications.…”