Growth and dielectric characterisation of large grain BiFeO3 thin films on amorphous SiO2 substrates

Paper in proceeding, 2010

The BiFeO3 (BFO) thin films have been grown by pulsed laser deposition technique on fused silica substrates with pre-patterned inter-digital Au electrodes. The surface images reveal that with increasing growth temperature some needle-shaped grains develop rapidly from the electrode edges in the film plane and at 600 degrees C fill up the 6 gm gap between the electrodes. The x-ray diffraction patterns reveal BFO (001) peaks and additional peaks associated with Bi and Fe oxides. The dielectric response of the BFO films is measured as a function of external dc field up to 200 kV/cm at 10 MHz, and in the frequency range 0.01-45 GHz without dc field. The capacitance-voltage dependence reveals typical ferroelectric behaviour with a coercive field approximately 60 kV/cm. The permittivity (24) of non-poled BFO films is rather frequency independent, at least up to self resonance frequency (about 15 GHz) of the inter-digital test structure including BFO film. The loss tangent increases with frequency and is less than 0.02 at 1 GHz. It is found that the normal magnetic field 0.2 T decreases permittivity of non-poled BFO films approximately by 0.3%.