Inhomogeneous domain nucleation and growth in disordered ferroelectric capacitors observed by modified piezoresponse force microscopy

Inhomogeneous domain evolution in the polarization switching process of epitaxial ferroelectric SrRuO3/PbZr0.4Ti0.6O3/SrRuO3 capacitors was observed using piezoresponse force microscopy with a separate probe needle as a stable electric contact. The nucleation, the forward growth and the sideways growth of reversed domains were observed visually using a step-by-step switching approach. The nucleation occurred at particular sites which have their own activation energy, both at the early stage of switching and in the middle of switching. The domain wall velocity was 0.1-0.5 m s(-1) under an electric field of 90 kV cm(-1). The inhomogeneous nucleation and growth of domains and the Lorentzian distribution of the characteristic switching time in the switching behaviour demonstrate that the local field deviation due to dipole defects in our SrRuO3/PbZr0.4Ti0.6O3/SrRuO3 capacitors strongly affects the domain nucleation and wall motion.