Nature Communications
Nature Communications
5 years ago

Possible absence of critical thickness and size effect in ultrathin perovskite ferroelectric films

Possible absence of critical thickness and size effect in ultrathin perovskite ferroelectric films
Ying-Hao Chu, Mingqiang Li, Bin Feng, Ryo Ishikawa, Naoya Shibata, En-Ge Wang, Dapeng Yu, Peng Gao, Shulin Chen, Xiumei Ma, Heng-Jui Liu, Yuichi Ikuhara, Zhangyuan Zhang, Kaihui Liu, Jingmin Zhang, Yen-Lin Huang, Lei Liao
Although the size effect in ferroelectric thin films has been known for long time, the underlying mechanism is not yet fully understood and whether or not there is a critical thickness below which the ferroelectricity vanishes is still under debate. Here, we directly measure the thickness-dependent polarization in ultrathin PbZr0.2Ti0.8O3 films via quantitative annular bright field imaging. We find that the polarization is significantly suppressed for films <10-unit cells thick (∼4 nm). However, approximately the polarization never vanishes. The residual polarization is ∼16 μCcm−2 (∼17%) at 1.5-unit cells (∼0.6 nm) thick film on bare SrTiO3 and ∼22 μCcm−2 at 2-unit cells thick film on SrTiO3 with SrRuO3 electrode. The residual polarization in these ultrathin films is mainly attributed to the robust covalent Pb–O bond. Our atomic study provides new insights into mechanistic understanding of nanoscale ferroelectricity and the size effects.

Publisher URL: http://www.nature.com/articles/ncomms15549

DOI: 10.1038/ncomms15549

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