Low-temperature dynamics of ferroelectric domains in PbZr_(0.3)Ti_(0.7)O_3 epitaxial thin films studied by piezoresponse force microscopy

摘要

Dynamics of domain boundaries is expected to change drastically at low absolute temperatures but direct experimental information for this temperature range is still lacking. To clarify the mechanism of low-temperature domain dynamics, we studied the growth of ferroelectric domains in the temperature range 4.2-295 K using the out-of-plane piezoresponse mode of a cryogenic atomic force microscope (AFM). Nanoscale 180° domains were created in epitaxial PbZr_(0.3)Ti_(0.7)O_3 films by applying short voltage pulses between the conductive AFM tip brought into contact with the bare film surface and the bottom LaSr_(0.7)Mn_(0.3)O_3 electrode. A quantitative analysis of acquired piezoresponse images enabled us to determine the in-plane domain size as a function of the writing voltage and pulse duration. It is found that at all studied temperatures the dependence of this size on the pulse duration can be fitted by a logarithmic function, which indicates that the domain-wall velocity exponentially depends on the driving electric field. The theoretical analysis of experimental data shows that the observed low-temperature domain dynamics is consistent with the creep of domain boundaries occurring in the presence of defects and structural nanoheterogeneities.