Observation of Nanoscale180°Stripe Domains in FerroelectricPbTiO3Thin Films

We report the observation of periodic $180°$ stripe domains below the ferroelectric transition in thin films. Epitaxial ${\mathrm{P}\mathrm{b}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ films of thickness $d=1.6$ to 42 nm on ${\mathrm{S}\mathrm{r}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ substrates were studied using x-ray scattering. Upon cooling below $T_C$, satellites appeared around Bragg peaks indicating the presence of $180°$ stripe domains of period $\Lambda =3.7$ to 24 nm. The dependence of $\Lambda$ on $d$ agrees well with theory including epitaxial strain effects, while the suppression of $T_C$ for thinner films is significantly larger than that expected solely from stripe domains.