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

Peng Gao, Zhangyuan Zhang, Mingqiang Li, Ryo Ishikawa, Bin Feng, Heng Jui Liu, Yen Lin Huang, Naoya Shibata, Xiumei Ma, Shulin Chen, Jingmin Zhang, Kaihui Liu, En Ge Wang, Dapeng Yu, Lei Liao, Ying Hao Chu, Yuichi Ikuhara*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

114 Scopus citations

Abstract

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 PbZr 0.2 Ti 0.8 O 3 films via quantitative annular bright field imaging. We find that the polarization is significantly suppressed for films <10-unit cells thick (â 1/44 nm). However, approximately the polarization never vanishes. The residual polarization is â 1/416 μCcm â '2 (â 1/417%) at 1.5-unit cells (â 1/40.6 nm) thick film on bare SrTiO 3 and â 1/422 μCcm â '2 at 2-unit cells thick film on SrTiO 3 with SrRuO 3 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.

Original languageEnglish
Article number15549
JournalNature Communications
Volume8
DOIs
StatePublished - 6 Jun 2017

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