Effect of film thickness on ferroelectric properties of sol-gel-derived Pb(Ti, Al)O-3 thin films

Degradation of ferroelectric properties with decreasing film thickness is a common problem of PbTiO3 type ferroelectric thin films. We suspected that this degradation was caused mainly by oxygen vacancies that diffused from the film surface through the grain boundaries during firing. Thus we have attempted to substitute Al3+ for Ti4+ in PbTiO3 using a sol-gel method. In this study, the effect of the film thickness on the ferroelectric properties of Pb(Ti0.9Al0.1)O3-x thin films ranging from thickness of 637 to 169 nm was investigated, and the dielectric constant and leakage current were compared to those of PbTiO3. The ferroelectric properties of Pb(Ti0.9Al0.1)O3-x thin films did not change much when the film thickness was decreased, and good ferroelectric properties were maintained. The values of epsilon(r) and tan delta for a 169-nm-thick Pb(Ti0.9Al0.1)O3-x film were 365 and 0.0127, and the values of P-r and E-c were 15 mu C/cm(2) and 86 kV/cm, respectively.