Effect of Ni substitution on the optical properties of BiFeO3 thin films

This paper reports about single phase Ni-substituted (0-20 at%) BiFeO3 (BFO) thin films for future optoelectronic device applications. The effect of Ni substitution on the microstructure, ferroelectric and optical properties of spin-coated BFO thin films were investigated. The x-ray diffractionpeaks corresponding to the (012) and (110) planes were found to be gradually shifted towards the lower diffraction angle side with the increasing Ni substitution in BFO films. The strain values in the corresponding planes were found to be increasing sharply upto the 10 at%. The Ni substituted BFO films were found to have larger grain sizes compared to that of the pristine BFO film. The remnant polarization enhanced with the Ni substitutions and the 20 at% Ni substituted BFO films showed a 3.5 times higher remnant polarization than the pristine BFO films. The optical band gaps were found to be increasing from 2.85 to 3.18 eV with the increase in Ni substitution upto 5 at%. Raman and infrared absorption data confirmed that the Ni substitution at Fe sites induces structural distortion at both Fe sites and Bi sites in BFO films. Due to the structural distortion, ferroelectric and optical properties of BFO films were significantly modified.