Vacuum-ultraviolet ellipsometry spectra and structural properties of Pb(Zr,Ti)O3 films

Optical properties of PbZr_xTi_1 − xO₃ material have been actively studied in the visible and near band-gap region, but data in the vacuum-ultraviolet spectral region is rather scarce. In this work we focus on well known interband transitions for the perovskite materials, 2p → dγ, located in VUV spectral region. Dielectric functions of chemical solution deposited and sputtered PZT were obtained in the spectral range 1-8.8 eV. Differences between the absorption maxima for chemical solution deposited and sputtered PbZr_xTi_1 − xO₃ samples near Kahn-Leyendecker 2p → dγ interband transition were found and are interpreted by change of interatomic distances. This is confirmed by different lattice constants. In the case of PbZr_xTi_1 − xO₃ film with microcracks, the void fraction was estimated from the effective medium approximation. Direct band-gap energies appear to be nearly the same for all reactive sputtered samples weakly depending of Zr/Ti concentration.