Double hysteresis loop induced by defect dipoles in ferroelectric Pb(Zr0.8Ti0.2)O3 thin films

Pb(Zr0.8Ti0.2)O-3 (PZT80/20) thin films were deposited on the Pt(111)/Ti/SiO2/Si(100) substrates by RF magnetron sputtering. Mainly perovskite crystalline phase with highly (202)-preferred orientation, determined by x-ray diffraction, was formed in the lead zirconate titanate (PZT)(80/20) thin films. Polarization measurements of the unannealed and aged films showed a clear double hysteresis loop. However, the double hysteresis loop phenomenon was greatly suppressed in the PZT thin films annealed under pure oxygen, and thus they exhibited larger remnant polarization (P-r 6.3 mu C/cm(2)). The related mechanism for the appearance of constricted and double hysteresis loops was investigated to be associated with the realignment and disassociation of defect dipoles via oxygen octahedral rotations or oxygen vacancy diffusion. The butterfly-shaped C-V characteristic curve with a valley gave further evidence for double hysteresis loop characteristic in the unannealed and aged PZT thin films. (c) 2011 American Institute of Physics. [doi:10.1063/1.3549116]