Effect of film thickness on ferroelectric properties of SOL-GEL DERIVED Pb(Ti,Nb)O₃ type thin films

Abstract

We investigated the relationship between the film thickness and ferroelectric properties for Pb(Ti_0.95Nb_0.05)O₃ thin films less than 260 nm thick, and examined a firing process to prevent existence of pyrochlore phase. The thin films were prepared using a sol-gel spincoat method onto platinum substrates. When the film thickness ranged from 260 to 160 nm, the films showed ferroelectricity. With decreasing the film thickness from 160 to 50 nm, however, dielectric constant decreased and degradation of ferroelectricity could be seen, because an amount of non-ferroelectric pyrochlore phase increased. Rapid thermal annealing (RTA) treatment in firing was effective to promote the phase transformation from pyrochiore to perovskite, but perovskite single phase structure could not be obtained in this study. The dielectric constant, the dissipation factor, remanent polarization and coercive field were ε = 397, tan δ = 0.019, Pr = 13 μC/cm² and Ec = 73 kV/cm, respectively, for 260 nm thick film that was RTA treated at 600°C for 1 min in O₂ flow.

Key Words:

• Sol-gel
• lead titanate
• thin film
• ferroelectric properties
• niobium doping
• film thickness