Fig. 1: PFM analyses of high-density BFO nanoislands.
From: Observation of multi-order polar radial vortices and their topological transition
a Topography of BFO (001) thin film with self-assembled nanoislands. b X-ray diffraction results showing the pseudocubic 002 peaks of the films. c Reciprocal space map recorded around the LSAT 002 Bragg peaks. d, e Vertical PFM amplitude (V-amp.) and vertical PFM phase (V-pha.) images of the domain patterns in the BFO film. f Enlarged OOP phase image superimposed with the topography image. g OOP phase image of one BFO nanoisland. h, i Height and vertical PFM phase spacing profiles along the yellow line in (g). The hump denoted by blue ellipse in (h) is derived from the additional adsorbates from air.
