A COMPARATIVE-STUDY ON THE ELECTRICAL-CONDUCTION MECHANISMS OF (BA0.5SR0.5)TIO3 THIN-FILMS ON PT AND IRO2 ELECTRODES

Electrical conduction mechanisms for Pt/(Ba0.5Sr0.5)TiO3 (BST)/Pt, IrO 2/BST/IrO2, and Pt/BST/IrO2 capacitors were studied. The Pt/BT/Pt capa citor shows a Schottky emission behavior with interface potential barr ier heights of about 1.5-1.6 eV. The barrier height is largely determi ned by the surface electron trap states of the BST. The IrO2/BST inter face shows an ohmic contact nature due to the elimination of the surfa ce trap states as the result of the formation of strong chemical bonds between the IrO2 and BST which results in the Poole-Frenkel emission conduction mechanism. Pt/BST/IrO2 capacitor shows Schottky emission be havior and a positive temperature coefficient of resistivity (PTCR) ef fect depending on the bias polarity. The electron trap states at the P t/PST interface and the positive space charges within the carrier depl etion layer result in the PTCR effect. (C) 1998 American Institute of Physics. [S0021-8979(98)05307-9].