Intrinsic nucleation mechanism and disorder effects in polarization switching on ferroelectric surfaces.

The temperature dependence of ferroelectric domain nucleation in epitaxial films of BiFeO3 is studied using variable temperature ultrahigh vacuum piezoresponse force spectroscopy in the 50 to 300 K temperature range. The nucleation bias corresponding to the onset of local ferroelectric switching in the volume of an electrostatic field confined by the metal tip was found to change less than 20% across the entire temperature range. A combination of the analytical and phase-field analysis proves that the weak temperature dependence of nucleation bias is a hallmark of an intrinsic nucleation mechanism with minimal contribution of thermal fluctuations. The effect of disorder on the observed distribution of the nucleation bias between vacuum and ambient environments is compared.