Far-infrared properties of sol–gel derived PbZr0.52Ti0.48O3 thin films on Pt-coated substrates

Abstract

Polycrystalline tetragonal PbZr0.52Ti0.48O3 (PZT) thin films have been deposited on the nickel and (111) platinum coated (110) sapphire substrates by the sol–gel method.Optical properties of the PZT thin films were studied using far-infrared reflectivity spectroscopy in the 200–10 000 cm−1 frequency range at 300 K. The frequency dependence of the optical characteristics (σ, ε, −Im ε−1) of the films were calculated by the Kramers–Kronig transformation of the reflectivity spectra and analysed by the Drude–Lorentz model. The frequency dependence of the optical conductivity, σ(ω), of the PZT films deposited on platinum coated sapphire is well described by the free-carrier term and an overdamped mid-infrared component. Sapphire/Pt/PZT structures reveal semiconductor properties (effective carrier concentration N/m* is up to 1020 cm−3, plasma minimum is located near 3000 cm−1). This effect can be related to the favourable influence of the platinum electrode on the charge carrier density at Pt/PZT contact and formation of the interfacial conductive layer.