Homogeneous switching in ultrathin ferroelectric films.

It is well known that there are two possible switching mechanisms in ferroelectric crystals and films (see, e.g., Tagantsev et al 2010 Domains in Ferroic Crystals and Thin Films (Berlin: Springer)). The first mechanism, which follows from the mean-field theory of Landau-Ginzburg, is a homogeneous one and does not connect domains. This mechanism was never observed before 1998. The second mechanism, connected with nucleation and domain movement, is common for the ferroelectrics and is well known from the time of domain discovery (1956). In the present paper the existence of a homogeneous mechanism of switching in ultrathin copolymer films is confirmed by piezoresponse force microscopy. The results of the present paper permit us to suppose that homogeneous switching exists in other ultrathin ferroelectric films.