Fig. 1: Formation of nanoscale 180° domains in strained PZT_MPB thin films.

a ISHG signal evolution during the ongoing growth of PZT_MPB on SRO-buffered NSO (red symbols) and at halted growth (black symbols). The insets illustrate the prevailing domain configurations during and after growth. b Reciprocal space map (out-of plane Q_⊥ vs. in-plane Q_||) around NSO 420 and PZT_MPB 103. The PZT_MPB film is fully strained with an extracted tetragonality c/a of 1.04. The dashed vertical lines indicate the main peak and satellite peak positions. c Cross-section at fixed Q_⊥ across the intensity distribution around the PZT_MPB 103 reflection. d HAADF-STEM image with overlaid ferroelectric dipole map viewed along the [010] zone axis. The yellow arrows reveal the presence of oppositely polarized 180° domains delimited by the dashed white lines. The white arrows represent the net polarization of each nanodomain. Scale bar, 4 nm.