Extended Data Fig. 8: Evolution of PFM response by using different a.c. (Vac) and d.c. (Vdc) voltages.
From: Bevel-edge epitaxy of ferroelectric rhombohedral boron nitride single crystal
a,b, PFM signals with a fixed Vdc of 8 V and various Vac of 0.8 V to 2.0 V (a), as well as a fixed Vac of 1 V and Vdc ranging from 2.0 V to 9.0 V (b). The Vdc-dependent PFM hysteresis loops show that the rBN system has a specific coercive voltage (Vc). When Vdc is smaller than Vc in rBN, Vdc is not enough to switch the ferroelectric polarization, so a butterfly shaped curve in amplitude and 180° phase hysteresis are absent. In addition, the PFM loops show increasing amplitude and shrinking hysteresis window with increasing Vac from 0.5 V to 2.0 V. c, PFM signals collected at different nine samples, indicating the reproducibility of ferroelectricity in rBN layers.
