Fig. 3. SHG and PFM of InSe:Y.

a SHG intensity at angles of 0⁰, 20⁰, and 30⁰. The inset gives the exfoliated InSe:Y morphology with the thickness of ~50 nm measured by atomic force microscopy (AFM). b Polar plots of SHG intensities collected by rotating the polarizer as a function of the detection angle. c Schemes of the InSe:Y film structure and the setup for the PFM measurement. The local PFM amplitude (d) and phase (e) loops during the switching process of the InSe:Y flake with thickness of ~50 nm (results of four cycles). f IP PFM amplitude at low frequencies together with the IP phase image as inset.