Non-conventional mechanism of ferroelectric fatigue via cation migration

• Published in: Nature communications 2019-07, Vol.10 (1), p.3064-8, Article 3064
• Main Authors: Ievlev, Anton V., KC, Santosh, Vasudevan, Rama K., Kim, Yunseok, Lu, Xiaoli, Alexe, Marin, Cooper, Valentino R., Kalinin, Sergei V., Ovchinnikova, Olga S.
• Format: Article
• Language: English
• Subjects: 140/58; 147/3; 639/301/119/996; 639/301/930/12; Atomic force microscopy; Atomic properties; Bias; Chemical elements; Computer simulation; Cycles; Degradation; Density functional theory; Electric fields; Electrodes; Experiments; Ferroelectric materials; Ferroelectricity; Humanities and Social Sciences; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Laboratories; Mass spectrometry; Mass spectroscopy; Materials fatigue; MATERIALS SCIENCE; Microscopy; multidisciplinary; Organic chemistry; Polarization; Properties (attributes); Science; Science (multidisciplinary); Scientific imaging; Thin films
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-11089-w

The unique properties of ferroelectric materials enable a plethora of applications, which are hindered by the phenomenon known as ferroelectric fatigue that leads to the degradation of ferroelectric properties with polarization cycling. Multiple microscopic models explaining fatigue have been suggested; however, the chemical origins remain poorly understood. Here, we utilize multimodal chemical imaging that combines atomic force microscopy with time-of-flight secondary mass spectrometry to explore the chemical phenomena associated with fatigue in PbZr 0.2 Ti 0.8 O 3 (PZT) thin films. Investigations reveal that the degradation of ferroelectric properties is correlated with a local chemical change and migration of electrode ions into the PZT structure. Density functional theory simulations support the experimental results and demonstrate stable doping of the thin surface PZT layer with copper ions, leading to a decrease in the spontaneous polarization. Overall, the performed research allows for the observation and understanding of the chemical phenomena associated with polarization cycling and their effects on ferroelectric functionality. Ferroelectric fatigue degrades ferroelectric properties upon polarization cycling, but its underlying chemistry is poorly understood. Here, the authors show by multimodal chemical imaging that fatigue in PbZr0.2Ti0.8O3 thin films is associated with Cu + ions migration from the electrode into the film structure.