Growth temperature dependent dielectric properties of BiFeO3 thin films deposited on silica glass substrates

We have studied the dependence of dielectric properties on the deposition temperature of BiFeO3 thin films grown by the pulsed laser deposition technique. Thin films have been grown onto amorphous silica glass substrates with pre-patterned Au in-plane capacitor structures. It is shown that on the amorphous glass substrate, BiFeO3 films with a near-bulk permittivity of 26 and coercive field of 80 kV/cm may be grown at a deposition temperature of about 600 degrees C and 1 Pa oxygen pressure. Low permittivity and higher coercive field of the films grown at the temperatures below and above 600 degrees C are associated with an increased amount of secondary phases. It is also shown that the deposition of BiFeO3 at low temperature (i.e. 500 degrees C) and post deposition ex-situ annealing at elevated temperature (700 degrees C) increases the permittivity of a film. The applied bias and time dependence of capacitance of the films deposited at 700 degrees C and ex-situ annealed films are explained by the de-pinning of the ferroelectric domain-walls.