Influence of Vanadium Doping on Structural and Ferroelectric Properties of Laser Ablated SrBi2Ta2O9 Thin Films

Abstract

AbstractPulsed laser deposition technique was used to fabricate SrBi2Ta2O9 (SBT) thin films with partial replacement of penta-valent vanadium ion. In this report, we have doped certain concentrations (0, 5, 10, 15 %) of vanadium at Ta-site of SBT thin films and study their influence on the structural and electrical characteristics. Thin films were grown on platinized silicon substrates using an excimer laser (KrF, 248 nm) with an energy density of ∼ 2.5 J/cm2. Xray diffraction studies confirmed the c-axis suppression of the films at lower processing temperature and at higher annealing temperatures. The decrease in the lattice parameter with vanadium doping was attributed to the smaller ionic radii of vanadium in comparison to Ta. Raman modes of SBT thin films shifted to higher frequencies upon vanadium incorporation at Ta-site. The extra Raman mode observed around ∼860 cm-1, was attributed due to the octahedron stretching vibration in the presence of vanadium at the center of octahedral cage. SBT thin films with 5% V doping exhibit enhanced ferroelectric properties, and the ferroelectric properties were degraded for higher vanadium concentration. The SBT thin films show dielectric constant of about ∼258 with tangential loss of 0.02 at a frequency of 100 kHz. Dielectric constant decreases with increase in V-concentration and attributed to the interdiffusion of bismuth into platinum electrode. The leakage current density of the films was also increased upon vanadium incorporation in SBT thin films.