Structural, dielectric, ferroelectric and optical properties of PBCT, PBST and PCST complex thin films on LaNiO₃ metallic conductive oxide layer coated Si substrates by the CSD technique

Highlights: • (1 1 0) Textured LNO thin films was grown on Si substrate. • Ferroelectric thin films on the LNO layer showed good electrical properties. • Ferroelectric thin films showed a direct allowed optical transition. • PBCT60, PBST60 and PCST60 films was grown on LNO/Si. - Abstract: Ferroelectric thin films and LaNiO₃ (LNO) metallic conductive oxide thin films were prepared by a chemical solution deposition (CSD) method. PBCT60, PBST60 and PCST60 ferroelectric thin films were grown on different structures such as LNO/Si and single-crystalline quartz SiO₂ (X-cut) substrates. The LNO layer acts as the bottom electrode for the electrical measurements. X-ray diffraction (XRD) analysis shows that LNO thin films on Si substrates and PBCT60, PBST60 and PCST60 thin films on LNO/Si structures are polycrystalline with a moderate (1 1 0)-texture and a complete perovskite phase. LNO, PBCT60, PBST60 and PCST60 thin films have a continuous, dense and homogenous microstructure with a grain size on the order of 50–80 nm. Electrical resistivity-dependence temperature data confirm that LNO thin films display a good metallic character over a wide large range of temperatures. Optical characteristics of PBCT60, PBST60 and PCST60 thin films have also been investigated using ultraviolet–visible (UV–vis) spectroscopy in the wavelength range of 200–1100 nm. Ferroelectric thin films show a direct allowed optical transition with optical band gap values on the of order of 3.54, 3.66 and 3.89 eV for PBCT60, PCST60 and PBST60 thin films deposited on a SiO₂ substrate, respectively. Good dielectric and ferroelectric properties are reported for ferroelectric thin films deposited on the LNO layer as bottom electrodes. Au/PBCT60/LNO/Si, Au/PBST60/LNO/Si and Au/PCST60/LNO/Si multilayer structures show a hysteresis loop with remnant polarization, P_r, of 9.6, 6.6 and 4.2 μC/cm² at an applied voltage of 6 V for PBCT60, PBST60 and PCST60 thin films, respectively