INFLUENCE OF SURFACES ON THE DIELECTRIC-PROPERTIES AND LEAKAGE CURRENTS IN PARAELECTRIC (PB0.72LA0.28)TIO3 THIN-FILMS

In the voltage range of 0-30 V, dielectric and leakage current density (J(L)) behavior were studied in paraelectric (Pb,La)TiO3 or PLT thin films (0.1-0.36 mu m) with bulk resistivity of 5.6x10(8) Omega-cm. With Pt electrodes, the properties were found to be contact dominated. With both top and bottom Pt electrodes, the interfacial capacitance (C-i) and the built-in voltage (V-bi) of the Schottky barrier were 380 pF and 1.3 V, respectively. A log-log plot of J(L) vs V exhibit slope of similar to 1 and 9, respectively, in the range of V<10 and 10< V<30. In the former voltage regime, the spatial dependence of the space charge density and therefore the electric field, makes analysis and interpretation of J(L) behavior nontrivial. Note that a slope of similar to 1 may be misconstrued as ohmic behavior. In the 10<V<30 voltage regime, the Schottky emission expression was modified to account for the interfacial space charge layer widening with voltage. A linear In J(L) vs V-1/4 plot coupled with a Schottky barrier potential of 1.5 V, indicated that Schottky emission process was operational at the interface. Due to a similar voltage dependence, however, Poole-Frenkel emission cannot be ruled out.