Effect of (Bi,Gd)FeO3 layer thickness on the microstructure and electrical properties of BiFeO3 thin films

Abstract

BiFeO3/(Bi,Gd)FeO3 (BFO/BGFO) bilayered thin films with different BGFO layer thicknesses were grown on SrRuO3/Pt/ TiO2/SiO2/Si(100) substrates using radio frequency sputtering. The grain size of BFO layer changes with the thickness of BGFO layer, and the BGFO layer decreases the leakage current density of BFO. The electrical properties of BFO/BGFO are tailored by changing the BGFO layer thickness. The dielectric constant (εr) of BFO/BGFO decreases with increasing BGFO layer thickness, owing to a smaller εr value of BGFO. The BFO206/BGFO150 layer has better ferroelectric properties (2Pr ∼ 137.7 μC/cm2 and 2Ec ∼ 722.0 kV/cm) due to the enhancement in (111) orientation and a denser microstructure. All bilayers have a much better fatigue behavior than that of BFO single layer. Moreover, the fatigue behavior of BFO/BGFO is dependent on the film orientation induced by different BGFO layer thicknesses, and the BFO206/BGFO220 bilayer exhibits a best fatigue endurance due to the (100) orientation. The fatigue mechanisms are illuminated by the frequency-dependent dielectric behavior and the resistivity as well as the leakage behavior before and after fatigue. As a result, the bilayer structure is an effective way to improve the electrical behavior of bismuth ferrite. © 2011 The American Ceramic Society.