Fig. 4: Polarization retention over a duration of >1 year showing no degradation over time in comparison to other ferroelectric systems.

a Out-of-plane PFM amplitude images of domains of different diameters recorded at the times indicated. The domains were fabricated by a tip voltage of −9 V with different pulse duration times (from right to left: 5 ms, 10 ms, 20 ms, 50 ms, 100 ms, and 200 ms). The needle-like rhombohedral variants are formed around the tetragonal domains concomitantly during the switching, as observed previously⁶¹. b Domains of various diameters and their change over time spanning 8904 h showing excellent polarization retention. The data are extracted from a and fitted by the modified 2D-Gaussian method. In another separately poled region, the domains poled with 300 ms at −9 V with a different tip display a no-decay trend of the polarization during the first 2000 h. The error bar shown here represents the standard error for each data point fitted by the modified 2D-Gaussian method. c A comparison of normalized retained polarization versus relaxation time between BiFeO₃ thin film in this study and other ferroelectric materials in previous reports, showing superior retention performance. The solid blue data points show the retention behaviour in the preliminary 2100 h and the solid black data points show the retention behaviour over 8900 h. Please note that all the legends shown below the figures are for Fig. 4c.