posted on 2021-05-21, 13:38authored byFei Zhou, Yang Li, Xingqi Liao, Shuren Lin, Haizeng Song, Yin Liu, Fuyi Yang, Shancheng Yan, Zhonghong Lai, Yong Liu, Cheng-Yan Xu, Zhihua Yang, Yudong Huang, Liang Zhen, Jingchuan Zhu, Jie Yao
Here,
we report a novel topotactic method to grow 2D free-standing
perovskite using KNbO3 (KN) as a model system. Perovskite
KN with monoclinic phase, distorted by as large as ∼6 degrees
compared with orthorhombic KN, is obtained from 2D KNbO2 after oxygen-assisted annealing at relatively low temperature (530
°C). Piezoresponse force microscopy (PFM) measurements confirm
that the 2D KN sheets show strong spontaneous polarization (Ps) along [101̅]pc direction
and a weak in-plane polarization, which is consistent with theoretical
predictions. Thickness-dependent stripe domains, with increased surface
displacement and PFM phase changes, are observed along the monoclinic
tilt direction, indicating the preserved strain in KN induces the
variation of nanoscale ferroelectric properties. 2D perovskite KN
with low symmetry phase stable at room temperature will provide new
opportunities in the exploration of nanoscale information storage
devices and better understanding of ferroelectric/ferroelastic phenomena
in 2D perovskite oxides.