Periodic ferroelectric-ferroelastic 90° domain patterns with an unprecedented small domain periodicity of 27 nm were observed in thin PbTiO3 films grown on DyScO3 substrates. These patterns contain the narrowest possible a domains 6 nm wide that allow to preserve the lateral coherence in the films, producing highly ordered patterns visible by x-ray diffraction.
Vlooswijk, A. H. G., Noheda, B., Catalan, G., Janssens, J. A., Janssens, A., Barcones Campo, B., ... De Hosson, J. T. M. (2007). Smallest 90 degree domains in epitaxial ferroelectric films. Applied physics letters, 91(11), 112901-. https://doi.org/10.1063/1.2783274