Fig. 3: The effect of loading forces on polarizations and domains.
From: Reversible flexoelectric domain engineering at the nanoscale in van der Waals ferroelectrics
a Topography image of tip-induced indentations with different loading forces from 3–6 μN. b Corresponding strain gradients of the different indentations in (a). c PFM phase image of a CIPS flake at an indentation depth of 5 nm. The red dashed line indicates the in-plane anisotropic flexibility. d PFM phase image of a CIPS flake at an indentation depth of 17 nm. e Selected phase profile as sketched by the white dashed line in (d). A phase anomaly with a contrast of 300° indicates the emergence of -HP states in the CIPS. f Schematic of the trigonal symmetry of the CIPS lattice (left panel) and schematic of anisotropic flexibility along the <100> and <1–10> crystal axes (right panel). g Crystal structure of the -HP state in CIPS. The Cu ions migrate into the vdW gaps between layers under the tip-induced flexoelectric field.
