Ferroelectric properties of PbxSr1-xTiO3 and its compositionally graded thin films grown on the highly oriented LaNiO3 buffered Pt/Ti/SiO2/Si substrates

Thin films of ferroelectric PbxSr1-xTiO3 (PST) with x = 0.3 - 0.7 and graded composition were fabricated on LaNiO3 buffered Pt/Ti/SiO2/Si substrates by a sol-gel deposition method. The thin films crystallized into a single perovskite structure and exhibited highly (100) preferred orientation after postdeposition annealing at 650 degrees C. The grain size of PST thin films systematically decreased with the increase of Sr content. Dielectric and ferroelectric properties were investigated as a function of temperature, frequency, and dc applied field. Pb0.6Sr0.4TiO3 films showed a dominant voltage dependence of dielectric constant with a high tunability in a temperature range of 25-230 degrees C. The compositionally graded PST thin films with x=0.3-0.6 also showed the high tunability. The graded thin films exhibited a diffused phase transition accompanied by a diffused peak in the temperature variations of dielectric constants. This kind of thin films has a potential in a fabrication of a temperature stable tunable device. (c) 2006 American Institute of Physics.