Effect of Sc substitution on the structure, electrical, and magnetic properties of multiferroic BiFeO3 thin films grown by a sol-gel process

Abstract

Multiferroic BiFeO3 (BFO), Bi1-xScxFeO3 (BSF), and BiFe1-xScxO3 (BFS) (x=0.3 mol%) thin films are prepared on Pt/Ti/SiO2/Si substrates using a sol-gel technique. The effect of Sc substitution along with the annealing ambient (N2 and O2) on the structure, electrical, and magnetic properties of the films are reported. X-ray diffraction (XRD) analysis reveals that the films can be prepared with the single-phase perovskite structure by annealing at 700 °C for 10 min either in O2 or N2 ambient. The unit cell volume increases on the substitution of Sc, which are 61.39, 62.50, and 62.57 (Å)3 for BFO, BSF, and BFS, respectively. X-ray photoelectron spectroscopy (XPS) study reveals that the chemical environments of Bi and Fe are different in BFO, BSF, BFS films. Similarly, XPS spectra for Sc2p lines in BSF and BFS also have different peak positions; this indicates Sc doping has certain chemical impact on BSF and BFS films. Systematic studies of Sc substitution along with the effect of annealing ambient on the dielectric constant (ε) and dielectric loss (tan δ), leakage current, remnant polarization (Pr), coercive field (Ec), and magnetic properties of the films are carried out. The room temperature values of ε and tan δ at 1 kHz for BFO and BFS films annealed in N2 ambient are (∼208; 0.035) and (∼235; 0.023), respectively. The comparative value of leakage current for the BFO and BFS films at an applied field strength of 50 kV/cm are 2.997×10-4 and 1.87×10-5 A/cm2, respectively. Room temperature value of coercive magnetization for BFS films has one order small compared to that of the BFO films; this indicates BFS films are magnetically soft and more suitable for potential device applications. Finally, among the studied compositions, the BFS films annealed in N2 ambient show the best property. © 2008 Elsevier B.V. All rights reserved.