Fig. 1: Antiferroelectricity-coupled spontaneous strain in β’-In2Se3.
From: Two-dimensional ferroelasticity in van der Waals β’-In2Se3
a TEM image showing the characteristic nanostriped superstructure in 2H β’-In2Se3. b Atomic-resolution annular dark-field (ADF) STEM image of the nanostripes and the atomic displacement map showing antiferroelectric ordering. c Selected-area electron diffraction (SAED) patterns of the parent β (top) and the room-temperature β’ (bottom) phases. The nanostriped superstructure in β’-In2Se3 gives rise to satellite diffraction at n/8 \(1\bar{1}00\) corresponding to the characteristic nanostripe width of \(4{d}_{1\bar{1}00}\) (~1.4 nm). d In-plane lattice spacing as a function of temperature extracted from in situ XRD for both heating and cooling processes. The observed increase of \(\sqrt{3}{d}_{11\bar{2}0}^{\parallel }\) and decrease of \({d}_{1\bar{1}00}^{\perp }\) during β-to-β’ transition reflect the anisotropic spontaneous strain with lattice dilation (compression) along (perpendicular to) the β’-In2Se3 nanostripes.
