Fig. 3
Alternating polar and nonpolar domains in CH3NH3PbI3 crystal. a Lateral PFM mapping showing complete failure of SHO (marked by black dots) in nonpolar domains due to their lack of true piezoelectricity. b Vertical PFM mappings showing identical domain pattern consisting of high-response polar domains and low-response nonpolar domains. c Resonant frequency mapping of vertical PFM showing elastic contrast between polar and nonpolar domains and good resonance tracking. d Quality factor mapping showing substantially lower quality factor and thus higher energy dissipation in nonpolar domains. e Point-wise tuning of piezoresponse vs. frequency showing a point in high-response polar domain has dominant first harmonic response and negligible second harmonic one, while a point in low-response nonpolar domain has higher second harmonic response. f Comparison of first and second harmonic responses vs. AC voltages averaged over a number of points in high-response and low-response domains confirming the trend in e; and g AFM topography domain pattern with h first and i second harmonic mappings confirming opposite contrast of first and second harmonic response
