Super switching and control of in-plane ferroelectric nanodomains in strained thin films

With shrinking device sizes, controlling domain formation in nanoferroelectrics becomes crucial. Periodic nanodomains that self-organize into so-called ‘superdomains’ have been recently observed, mainly at crystal edges or in laterally confined nanoobjects. Here we show that in extended, strain-engineered thin films, superdomains with purely in-plane polarization form to mimic the single-domain ground state, a new insight that allows a priori design of these hierarchical domain architectures. Importantly, superdomains behave like strain-neutral entities whose resultant polarization can be reversibly switched by 90°, offering promising perspectives for novel device geometries. In ferroelectrics, domains of different polarization determine the switching behaviour and are therefore crucial to their practical use. Here, Matzen et al. observe the formation and control of superdomain arrangements of nanoscale domains in thin films that mimic the single-domain ground state.