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

doi:10.1038/ncomms15549

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 journal › Article › peer-review

137 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 language	English
Article number	15549
Journal	Nature Communications
Volume	8
DOIs	https://doi.org/10.1038/ncomms15549
State	Published - 6 Jun 2017

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Gao, P., Zhang, Z., Li, M., Ishikawa, R., Feng, B., Liu, H. J., Huang, Y. L., Shibata, N., Ma, X., Chen, S., Zhang, J., Liu, K., Wang, E. G., Yu, D., Liao, L., Chu, Y. H., & Ikuhara, Y. (2017). Possible absence of critical thickness and size effect in ultrathin perovskite ferroelectric films. Nature Communications, 8, Article 15549. https://doi.org/10.1038/ncomms15549

@article{5f3a47e5fc4f422a9fee97dacf1a9a54,

title = "Possible absence of critical thickness and size effect in ultrathin perovskite ferroelectric films",

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 ({\^a} 1/44 nm). However, approximately the polarization never vanishes. The residual polarization is {\^a} 1/416 μCcm {\^a} '2 ({\^a} 1/417%) at 1.5-unit cells ({\^a} 1/40.6 nm) thick film on bare SrTiO 3 and {\^a} 1/422 μCcm {\^a} '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.",

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

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year = "2017",

month = jun,

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doi = "10.1038/ncomms15549",

language = "English",

volume = "8",

journal = "Nature Communications",

issn = "2041-1723",

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T1 - Possible absence of critical thickness and size effect in ultrathin perovskite ferroelectric films

AU - Gao, Peng

AU - Zhang, Zhangyuan

AU - Li, Mingqiang

AU - Ishikawa, Ryo

AU - Feng, Bin

AU - Liu, Heng Jui

AU - Huang, Yen Lin

AU - Shibata, Naoya

AU - Ma, Xiumei

AU - Chen, Shulin

AU - Zhang, Jingmin

AU - Liu, Kaihui

AU - Wang, En Ge

AU - Yu, Dapeng

AU - Liao, Lei

AU - Chu, Ying Hao

AU - Ikuhara, Yuichi

PY - 2017/6/6

Y1 - 2017/6/6

N2 - 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.

AB - 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.

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U2 - 10.1038/ncomms15549

DO - 10.1038/ncomms15549

M3 - Article

C2 - 28585548

AN - SCOPUS:85020428339

SN - 2041-1723

VL - 8

JO - Nature Communications

JF - Nature Communications

M1 - 15549

ER -

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

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