Structural and electrical characteristics of Pb_0.90La_0.15TiO₃ thin films on different bottom electrodes

Abstract

Pb_0.90La_0.15TiO₃ (PLT15) thin films were deposited by the sol-gel method on Pt, Pt/Si, and RuO₂ on Si and Pt/Si bottom electrodes. X-ray diffraction, micro-Raman spectroscopy, and atomic force microscopy techniques were used for structural characterization of these films. PLT15 films on different electrodes showed good surface morphology with dense and uniform microstructure. PLT15 films on solution derived RuO₂ bottom electrodes show (100) preferred orientation of growth and result in larger crystallites. Films deposited on a Pt bottom electrode show sharp and intense Raman features indicating better crystallinity and insignificant film-electrode interactions. PLT15 film on a Pt bottom electrode exhibited higher dielectric constant (1300 at 100 kHz) and high values of P_m and P_r, 68 and 46 µ C/cm², respectively, compared to other electrodes. Films on a RuO₂ bottom electrode showed relatively inferior dielectric and ferroelectric properties. The ac field dependence of dielectric permittivity at subswitching fields was fitted using the Rayleigh law. It was found that ~22% of the total measured permittivity was due to irreversible domain wall displacement for the films on a Pt electrode. The reversible polarization components estimated from the capacitance-voltage (C-V) and quasistatic hysteresis measurements showed that P_rev/P_sat at V_max for the case of Pt/Si (24%), was larger than that of Pt (11%) bottom electrodes. The observed results were correlated with the domain wall pinning at the disturbed film-electrode interface.