Infrared reflectivity study of Cu-doped PbTiO3 and PbZr0.52 Ti0.48O3 ferroelectric thin films

Monocrystalline c-axis oriented thin films of PbTiO3 with various hole concentration were prepared by Cu doping with 0.1, 0.5, 1.0 mas.% and substituting Zr for Ti (Zr:Ti equals 52:48). We report concentration-dependent far- and mid- infrared reflectivity spectra of these compounds focusing on the electronic properties. Optical functions (ε 1, ε 2, σ , -Im ε -1) have been analyzed by Kramers-Kronig transformation to reflectivity spectra measured in a frequency range of 200 - 10000 cm-1 at room temperature. Conductivity spectra show a complete semiconducting dependence that can be analyzed by Drude-Lorentz model and in the terms of dynamic interaction, which leads to a frequency dependent scattering rate and enhanced low-frequency carrier mass 0.5 mas.% Cu in PbTiO3 decreases effective mass from 3.5 to 1.5 near 200 cm-1 and increases relaxation time as compared with the undoped sample.