Theoretical description of ferroelectric and pyroelectric hystereses in the disordered ferroelectric-semiconductor films

We have modified the Landau-Khalatnikov approach and shown that both the polar lattice and the screened charged defects determine the response of disordered ferroelectric semiconductors. This system exhibits the spatially inhomogeneous switching under the external field while the Landau-Khalatnikov model describes homogeneous switching with the sharp pyroelectric coefficient peak near the thermodynamic coercive field value. Our model gives more realistic pyroelectric hysteresis loop shape without any peaks near the coercive field and describes both qualitatively and quantitatively typical Pb(Zr,Ti)O3 and (Sr,Ba)Nb2O6 films pyroelectric hysteresis loops.