Structural and multiferroic properties of BiFeO3 thin films at room temperature

BiFeO3 thin films have been prepared on Pt/TiO2/SiO2/Si substrates under various oxygen pressures of 0.15-0.005 Torr at a temperature of 450degreesC by pulsed-laser deposition. The effects of deposition pressure on their crystal structure and multiferroic properties have been investigated at room temperature. X-ray diffraction analysis (theta-2theta scans and 2-dimensional scans) shows that the BiFeO3 thin films consist of perovskite single phase with tetragonal crystal structure and space group P4mm. The c-axis lattice constant decreases (4.062-4.006 Angstrom) and c/a ratio of the films decreases from 1.032 to 1.014 with a decrease in the oxygen pressure. The surface roughness and grain size of the films depend dramatically on oxygen pressures. The dielectric constant of the films decreases with decreasing oxygen pressure. The film deposited at 0.05 Torr shows a stable current density and well-saturated hysteresis loop with twice the remanent polarization (2P(r)) of 136 muC/cm(2) and coercive field (2E(c)) of 109 kV/cm. The BiFeO3 thin films also show the saturated weak ferromagnetic hysteresis loops with a small remanent magnetization. (C) 2004 American Institute of Physics.