Ferroelectric materials exhibit spontaneous and switchable electric polarization in the absence of external electric field. Polarization in thin layers of ferroelectrics in a ferroelectric/dielectric superlattice forms into vertical striped nanodomains that have a serpentine--like spatial structure along the in--plane directions. The ubiquity of the serpentine striped structure in a large variety of systems including block copolymers and magnetic domains suggest that there may exist a general physical model that describes these systems, and understanding this physical model will bring us one step closer to controlling the formation and dynamics of ferroelectric nanodomains. Here we show using coherentx--ray scattering techniques (x-rayphoton correlation spectroscopy) that domain patterns in a PbTiO3/SrTiO3superlattice decorrelate on a time scale of about 1000 s at room temperature at thermal equilibrium. The decorrelation is likely caused by the transition between energetically degenerate states driven by the thermal energy kT. The temporal decorrelation of the domain patterns can be described using a compressed exponential function exp -(τ /τ s)1.5 which is the function widely used to describe the fluctuation of spatial structure in various systems with jammed spatial disorder including ‘soft’ materials such as block copolymers and ‘hard’ materials such as antiferromagnetic domains. In addition, the characteristic time of the fluctuation can be tuned by repetitive application of electric pulses. The ultrafast photo-induced strain on BiFe03 thin films from a focused laser pump and the nanodiffraction from domains in FIB patterns as small as 350nm on the superlattice will also be discussed.
Type Of Event
Dr. Qingteng Zhang, University of Wisconsin, Madison