Impedance/Modulus Analysis of Sol-gel BaxSr1-xTiO3 Thin Films

Perovskite-structure-type sol-gel barium-strontium-titanate (BST) thin films with molar formula BaxSr1-xTiO3 (x = 0.5, 0.6, 0.7, and 0.8) have been successfully fabricated as Al/BST/Pt capacitors. In order to study the role of the grain size in the conduction mechanisms, we present atomic force microscopy (AFM) results. The impedance and the electric modulus of BaxSr1-xTiO3 thin films have been analyzed in order to correlate the effect of the film regional processes on the conduction mechanism. The impedance and the electric modulus complex planes show three overlapping regions as response for the bulk, the grain boundary and the film/electrode interface mechanisms, and an equivalent circuit has been proposed for each mechanism. The conduction mechanism resulting from the bulk and the grain boundaries is discussed; the results show that the grain boundaries have less effect on the conduction mechanism than the bulk.