(a) A PE amplitude hysteresis loop obtained atop a NW; (b) vertical PFM signals in pm/V from a NW subjected to local poling of ±10 V: (i) before, (ii) immediately after poling, and (iii) 30 min after poling; (c) vertical PFM signals in pm/V (same scale as in (b)), after local poling of the TF sample; (d) lateral PFM: (i) amplitude and (ii) phase obtained simultaneously with (c); (e) lateral PFM amplitude from the NW, obtained simultaneously with (b) (ii). The double arrow indicates the tip orientation during the scan.