Ferroelectric Sr2(Nb, Ta)2O7 Thin Films Prepared by Chemical Solution Deposition

Abstract

Ferroelectric Sr2(Nb, Ta)2O7 (SNTO) thin films were prepared by chemical solution deposition process, i.e. the modified sol-gel method. The stock solutions were spin-coated onto either Pt/Ti/SiO2/Si(100) or Pt/TiO2/SiO2/Si(100) substrate. After multiple coating/baking steps, dried thin film stacks were annealed for crystallization at 850–1000°C in oxygen. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses revealed that the crystallization temperature by modified sol-gel process can be lowered to 850°C if Pt/TiO2/SiO2/Si(100) substrate was used, while temperature higher than 950°C is required for Pt/Ti/SiO2/Si(100) substrate. Leakage current and relative permittivity (εr) values were measured in the range of about 10-9–10-7 A/cm2, and 30–45, respectively, depending on the composition, heat-treatment and substrate type. Polarization hysteresis loops were not saturated regardless of composition and annealing temperature. Remanent polarization (2Pr) and coercive field (Ec) values for typical SNTO(30/70) film were approximately 1.9 µC/cm2, and 17 kV/cm, respectively, when ±5 V pulse was applied.