Periodic nanodomains in PbTiO3 films under tensile strain

In epitaxial ferroelectric thin films under tensile strain, a transition from 180?? domains to 90?? domains can be achieved by increasing the film thickness. In many cases, the 90?? a/c domains appear in the form of wide c-domains separated by narrow a-stripes. We have deposited thin films of PbTiO3 on DyScO3 substrates and show that the condition of horizontal coherence forces the a-domains to adopt discrete sizes, the smallest of which is substrate-independent and depends only on the tetragonality of the ferroelectric film. Growing PbTiO3 on DyScO3, we have achieved the narrowest (6 nm) possible a-domains, as well as the shortest periodicity that allows to maintain the lateral coherence in the film.