Influence of surfaces on the dielectric properties and leakage currents in paraelectric (Pb_0.72La_0.28)TiO₃ thin films

Abstract

Abstract In the voltage range of 0–30 V, dielectric and leakage current density (JL ) behavior were studied in paraelectric (Pb,La)TiO3 or PLT thin films (0.1 −0.36 μm) with bulk resistivity of 5.6×108 Ω-cm. With Pt electrodes, the properties were found to be contact dominated. With both top and bottom Pt electrodes, the interfacial capacitance (Ci and the built-in voltage (Vbi ) of the Schottky barrier were 380 pF and 1.3 V, respectively. A log-log plot of JL vs V exhibit slope of ∼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 JL behavior nontrivial. Note that a slope of ∼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 ln JL vs V1/4 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.