A positive temperature coefficient of resistivity effect from a paraelectric Pt/(Ba0.5,Sr0.5)TiO3/IrO2 thin-film capacitor

A (Ba0.5,Sr0.5)TiO3 (BST) thin film was deposited on IrO2 thin-film electrode by a rf magnetron sputtering method. Top Pt electrode was deposited on the BST film to make a planar structured capacitor. The BST thin film showed paraelectric behavior at room temperature. A positive temperature coefficient of resistivity (PTCR) effect was observed when the conduction electrons were injected from the IrO2 electrode to BST, while Schottky emission behavior was observed when they were injected from the Pt electrode to BST. The electrical double layer formed at the Pt/BST interface results in the PTCR effect. A model that can explain the asymmetrical conduction behavior with respect to the bias polarity is suggested based on the energy band configurations at the interfaces with the electrodes.