Influence of Semiconducting Electrodes on Dielectric and Pyroelectric Properties of Ferroelectric Thin Films

The dielectric and pyroelectric properties of ferroelectric thin films coated with two semiconducting electrodes are studied in the frame work of Ginzburg-Landau-Devonshire theory. Due to the depolarization effect produced by the surface polar charges cannot be completely screened, the contribution of the semiconducting electrodes is included in the free-energy functional. The dielectric susceptibility and the pyroelectric coefficient are calculated respectively as functions of temperature and film thickness. A comparison with the results of investigations performed for perfectly conducting electrodes shows that the effects of semiconducting electrodes can induce a transition from the ferroelectric phase to paraelectric phase, changing the phase transition from the second order to first order, and greatly improving the dielectric susceptibility and pyroelectric coefficient.