Slim P-E hysteresis loop and anomalous dielectric response in sol-gel derived antiferroelectric PbZrO_3 thin films

摘要

Sol-gel derived PbZrO_3 (PZ) thin films have been deposited on Pt(111)/Ti/SiO_2/Si substrate and according to the pseudotetragonal symmetry of PZ, the relatively preferred (110), oriented phase formation has been noticed. The room temperature P-E hysteresis loops have been observed to be slim by nature. The slim hysteresis loops are attributed to the [110], directional antiparallel lattice motion of Pb ions and by the directionality of the applied electric field. Pure PZ formation has been characterized by the dielectric phase transition at 235 ℃ and antiferroelectric P-E hysteresis loops at room temperature. Dielectric response has been characterized within a frequency domain of 100 Hz-1 MHz at various temperatures ranging from 40 to 350 ℃. Though frequency dispersion of dielectric behaves like a Maxwell-Wagner type of relaxation, ω~2 dependency of ac conductivity indicates that there must be G-C equivalent circuit dominance at high frequency. The presence of trap charges in PZ has been determined by Arrhenius plots of ac conductivity. The temperature dependent n (calculated from the universal power law of ac conductivity) values indicate an anomalous behavior of the trapped charges. This anomaly has been explained by strongly and weakly correlated potential wells of trapped charges and their behavior on thermal activation. The dominance of circuit/circuits resembling Maxwell-Wagner type has been investigated by logarithmic Nyquist plots at various temperatures and it has been justified that the dielectric dispersion is not from the actual Maxwell-Wagner-type response.