AC properties of laser ablated La-modified lead titanate thin films

Abstract

Lanthanum-doped lead titanate (PLT) thin films were identified as the most potential candidates for the pyroelectric and memory applications. PLT thin films were deposited on Pt-coated Si substrates by excimer laser ablation deposition technique. The dielectric response of PLT thin films has been studied over a temperature range of 300-600 K. A universal power law relation was brought into picture to explain the frequency dependence of AC conductivity. The temperature dependence of AC conductivity was analyzed in detail. The activation energy obtained from the temperature dependence of AC conductivity was attributed to the shallow trap-controlled space charge conduction in the bulk of the sample. The impedance analysis combined with modulus spectroscopy was also performed to get insight of the microscopic features like grain, grain boundary and film-electrode interfaces and their effects in the film. The imaginary component of modulus M″ exhibited double peak at high temperatures. Different types of mechanisms were analyzed in detail to explain the dielectric relaxation behavior in the PLT thin films.