摘要
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.
原文 | English |
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文章編號 | 15549 |
期刊 | Nature Communications |
卷 | 8 |
DOIs | |
出版狀態 | Published - 6 6月 2017 |