Dielectric properties of (110) oriented PbZrO₃ and La-modified PbZrO₃ thin films grown by sol-gel process on Pt(111)/Ti/SiO₂/Si substrate

Abstract

Highly (110) preferred orientated antiferroelectric PbZrO₃ (PZ) and La-modified PZ thin films have been fabricated on Pt/Ti/SiO₂/Si substrates using sol-gel process. Dielectric properties, electric field induced ferroelectric polarization, and the temperature dependence of the dielectric response have been explored as a function of composition. The T_c has been observed to decrease by ~17° C per 1 mol% of La doping. Double hysteresis loops were seen with zero remnant polarization and with coercive fields in between 176 and 193 kV/cm at 80° C for antiferroelectric to ferroelectric phase transformation. These slim loops have been explained by the high orientation of the films along the polar direction of the antiparallel dipoles of a tetragonal primitive cell and by the strong electrostatic interaction between La ions and oxygen ions in an ABO₃ perovskite unit cell. High quality films exhibited very low loss factor less than 0.015 at room temperature and pure PZ; 1 and 2 mol% La doped PZs have shown the room temperature dielectric constant of 135, 219, and 142 at the frequency of 10 kHz. The passive layer effects in these films have been explained by Curie constants and Curie temperatures. The ac conductivity and the corresponding Arrhenius plots have been shown and explained in terms of doping effect and electrode resistance.