Surface effects on switching in ferroelectric films

Surface effects on switching behaviours of ferroelectric (FE) films are elucidated by using the Landau Devonshire (LD) free energy expression. The well-known parameter, ?, the extrapolation length, introduced in the LD free energy expression strongly influences the switching behaviours in FE films. Polarization at the surface can either be suppressed when ? is positive or be enhanced when ? is negative. We have discovered that the delay in switching at the centre relative to switching near the surfaces is more remarkable in the case of ? = 0 than the non-zero ? cases, as the film thickness increases. It is also found that the reversals of dipole moments at the centre and near the surface, by the applied field, take place almost together in FE thin films of non-zero ?. The results we obtained have shown that the surface extrapolation length ? also influences the critical thickness of FE films