Dielectric relaxation in antiferroelectric multigrain PbZrO₃ thin films

Abstract

Antiferroelectric materials are found to be good alternative material compositions for high charge storage devices and transducer applications. Lead zirconate (PZ) is a room temperature antiferroelectric material. Thin films of PZ with various thicknesses were deposited by excimer laser ablation technique on Pt coated Si-substrates at a substrate temperature of 300°C and, subsequently, post annealed at 650° C. The antiferroelectric nature of PZ thin films was studied over a temperature range 30-250° C. Effect of thickness on the net dielectric constant was studied in detail and the calculated interfacial dielectric layer thickness is 0.1 nm approximately, with a bulk dielectric constant of 222 at 100 kHz. Impedance and electric modulus formalisms were employed in order to gain an insight of the microstructural details of multigrain thin films. A comprehensive study on relaxation mechanism revealed that the Maxwell-Wagner type polarization is the basic relaxation phenomenon in the multigrain PZ thin films, due to the presence of multiple grain and grain boundaries across the film thickness. The activation energies from the interior grain relaxation and ac conductivity studies were 0.631 and 0.563 eV, respectively. These activation energies were attributed to the excitation of the charge carriers from a set of shallow traps and/or oxygen vacancies present at an average depth of 0.5-0.6 eV from the bottom of the conduction band.